SBA MCQ Flashcards

Question

A 32yo had a normal vaginal delivery 10 days ago. Her uterus has involuted normally. Choose the single most likely predisposing factor for PPH? a. Retained product b. Uterine infection c. DIC d. Von Willebrand disease e. Primary PPH

Answer 1

The single most likely predisposing factor for postpartum hemorrhage (PPH) in this case would be: a. Retained product Retained products of conception, such as placental fragments or membranes, can lead to postpartum hemorrhage by preventing the uterus from contracting adequately and achieving proper hemostasis. In this scenario, if the uterus has involuted normally but the patient still experiences postpartum hemorrhage, retained products of conception are a likely cause. Prompt identification and management of retained products are crucial to prevent complications associated with postpartum hemorrhage.

Answer 2

Based on the given scenario of significant bleeding and the patient’s vital signs, the estimated blood loss can be categorized as follows: BP=80/50 mmHg, pulse=130 bpm These vital signs indicate hypotension and tachycardia, which are signs of compensatory mechanisms in response to significant blood loss. Based on the clinical signs and symptoms, the estimated blood loss would likely fall within the range of: e. >50% The patient’s condition with significant hypotension and tachycardia suggests a massive hemorrhage, indicating a loss of more than 50% of circulatory blood volume. This level of blood loss is severe and requires urgent medical attention and resuscitation to prevent further complications and improve outcomes.

Answer 3

The most probable cause of cough, fever, and bilateral cavitating consolidation in an old alcoholic is: a. AFB (acid-fast bacilli) This presentation is highly suggestive of tuberculosis, especially in an older alcoholic individual. Tuberculosis commonly presents with cough, fever, and pulmonary infiltrates, which can progress to cavitation, particularly in individuals with risk factors such as alcoholism. Acid-fast bacilli (AFB) are characteristic of Mycobacterium tuberculosis, the causative agent of tuberculosis, and are typically seen on sputum microscopy or culture in affected individuals. Therefore, AFB is the most probable cause in this case.

Answer 4

The most probable diagnosis in this case is: c. Ischemic mitral regurgitation Ischemic mitral regurgitation occurs as a complication of myocardial infarction, particularly involving the papillary muscles or chordae tendineae. The dysfunction of these structures leads to incomplete closure of the mitral valve, resulting in regurgitation of blood from the left ventricle into the left atrium during systole. Pulmonary edema is a common manifestation of severe mitral regurgitation, as the backward flow of blood increases the volume and pressure within the left atrium and pulmonary vasculature, leading to pulmonary congestion and edema. Therefore, ischemic mitral regurgitation is the most probable diagnosis in this scenario, given the patient’s history of recent myocardial infarction and presentation with pulmonary edema.

Answer 5

The single investigation most likely to lead to the diagnosis in this case is: a. Sweat chloride test The presentation of a wasted appearance in a 3-year-old child with a history of chronic diarrhea, bulky, frothy stools, and difficulty flushing suggests the possibility of cystic fibrosis (CF). The sweat chloride test is the gold standard for diagnosing CF, as elevated chloride levels in sweat are characteristic of the condition. Therefore, performing a sweat chloride test would be the most appropriate initial investigation to confirm or rule out the diagnosis of CF in this child.

Answer 6

The most appropriate treatment for anaphylaxis, as described in this scenario, is: b. 0.25ml IM adrenaline Anaphylaxis is a severe allergic reaction that can lead to life-threatening symptoms such as stridor, wheezing, and erythematous rash. The first-line treatment for anaphylaxis is adrenaline (epinephrine) administered intramuscularly (IM). Adrenaline acts rapidly to reverse the symptoms of anaphylaxis by constricting blood vessels, relaxing bronchial smooth muscle, and improving cardiac output. Therefore, administering 0.25ml of IM adrenaline is the most appropriate immediate treatment in this case.

Answer 7

The most appropriate C-Section complication in this case, given the history of retained placenta requiring manual removal in the operating theater and the current presentation of intermittent vaginal bleeding, is: e. DIC (Disseminated Intravascular Coagulation) Disseminated intravascular coagulation (DIC) can occur as a complication of retained products of conception (POC), such as retained placenta. Manual removal of the placenta can lead to excessive bleeding and disruption of normal clotting mechanisms, resulting in DIC. The intermittent vaginal bleeding in this case may be indicative of ongoing bleeding secondary to DIC. Therefore, DIC is the most appropriate complication to consider in this scenario.

Answer 8

The most appropriate initial action in this patient, who presents with breathlessness, chest pain, and confirmed rib fractures on CXR after a head-on collision, is: c. O2 by mask Given the potential for underlying lung injury or pneumothorax secondary to rib fractures and the patient’s symptoms of breathlessness, providing oxygen by mask is crucial to optimize oxygenation and prevent hypoxia. This action takes priority in the initial management of trauma patients with suspected chest injuries. After ensuring adequate oxygenation, further assessment and management, including analgesia and referral to a surgeon if necessary, can be initiated. However, oxygen therapy is the most immediate and appropriate initial action in this scenario.

Answer 9

The most appropriate action for the 30-year-old man with a deep penetrating knife wound who reports having received tetanus toxoid (TT) vaccination when he left school is: b. Antibiotic While tetanus prophylaxis is important in cases of penetrating wounds, if the patient has received a complete primary vaccination series and a booster within the past 10 years, additional tetanus toxoid vaccination may not be necessary. However, administering antibiotics is crucial to prevent wound infection and other potential complications. Therefore, providing antibiotics would be the most appropriate immediate action for this patient.

Answer 10

The option that would likely be of concern is: b. She can’t make a sentence At 15 months of age, most children should be able to make basic sentences consisting of a few words. The inability to form sentences could be a developmental red flag and may indicate a language delay or other developmental issue. Therefore, this option would be the one that raises concern.

Answer 11

The medication that can help prevent the progression of chronic glomerulonephritis (GN) in this case is: b. ACEi (Angiotensin-Converting Enzyme inhibitor) ACE inhibitors have been shown to be effective in slowing the progression of chronic kidney disease, including chronic glomerulonephritis. They help by reducing intraglomerular pressure and proteinuria, thereby protecting the kidneys from further damage and slowing the decline in kidney function. Therefore, prescribing an ACE inhibitor would be a suitable choice to help manage this patient’s condition and prevent progression.

Answer 12

The most probable diagnosis in this case is: d. Subdural hemorrhage The presentation of progressive confusion, bruises on the arms, and an elevated INR level in a patient on warfarin suggests the possibility of a subdural hemorrhage. Warfarin predisposes patients to bleeding events, and an elevated INR increases the risk of hemorrhage, including subdural hemorrhage, which can present with symptoms such as confusion and bruising. Therefore, subdural hemorrhage is the most probable diagnosis in this scenario.

Answer 13

The clinical presentation and investigation results are highly suggestive of: Sickle Cell Anemia Explanation: • Recurrent episodes of severe pain in the joints and abdomen: These pain crises are characteristic of sickle cell anemia due to vaso-occlusion. • Fatigue, shortness of breath, and occasional dizziness: These symptoms are consistent with chronic hemolytic anemia, common in sickle cell disease. • Pallor and jaundice: These signs indicate hemolysis. • Splenomegaly and tenderness over long bones: Splenomegaly is common in children with sickle cell anemia due to sequestration crises, though the spleen may become fibrotic and reduce in size over time. Bone pain and tenderness are frequent due to bone infarctions. • Limited range of motion due to pain: This is typical during pain crises. • Haemoglobin: 70 g/L: This is indicative of severe anemia. • Reticulocyte Count: 8%: Elevated reticulocyte count reflects increased red blood cell production in response to hemolysis. • Serum Bilirubin: 43.4 µmol/L: Elevated bilirubin is a result of increased breakdown of red blood cells. • Blood Smear: Presence of Howell-Jolly bodies: Howell-Jolly bodies indicate asplenia or hyposplenia, often seen in sickle cell anemia due to repeated splenic infarctions. Therefore, the correct diagnosis is: Sickle Cell Anemia

Answer 14

The mass arising from the head of the pancreas is most likely compressing the supraduodenal common bile duct. This is because the head of the pancreas lies closely adjacent to the common bile duct, specifically the supraduodenal part, which is the portion of the common bile duct that runs above the duodenum before it enters and runs behind the pancreas. Compression of this duct by a pancreatic head mass is a common cause of obstructive jaundice. Therefore, the correct answer is: E Supraduodenal common bile duct

Answer 15

The description of a lump protruding from the abdomen into the groin and upper part of the scrotum suggests an inguinal hernia. Specifically, for the hernia to reach the scrotum, it must pass through the inguinal canal. The entrance to the inguinal canal from the abdominal cavity is the deep inguinal ring. Therefore, the correct answer is: A Deep inguinal ring

Answer 16

The discharging swelling over the belly button (umbilicus) in a patient with advanced carcinoma of the stomach suggests a Sister Mary Joseph nodule, which is a metastatic tumor deposit at the umbilicus. The pathway through which such metastases can occur is often related to the ligamentum teres, which is a remnant of the umbilical vein and runs from the umbilicus to the liver. Therefore, the correct answer is: D Ligamentum teres

Answer 17

The patient’s presentation with pain in the left shoulder tip, left lower chest, and left upper abdomen, along with free fluid under the left hemidiaphragm on a FAST scan, strongly suggests splenic injury. The referred pain to the left shoulder tip is characteristic of Kehr’s sign, which occurs due to irritation of the diaphragm. The phrenic nerve, which innervates the diaphragm, originates from cervical nerves C3-C5 and can refer pain to the shoulder tip. Therefore, the correct answer is: E Splenic rupture causing pain through the phrenic nerve

Answer 18

For postoperative analgesia following an operation for a fistula-in-ano, the most appropriate nerve to block is the pudendal nerve. The pudendal nerve provides sensory innervation to the perineum and the external genitalia, as well as motor innervation to the external anal sphincter and other pelvic floor muscles. Blocking this nerve will provide effective pain relief for procedures involving the anal and perineal region. Therefore, the correct answer is: E Pudendal nerve The pudendal nerve (S2, S3 and S4) in the perineum is the one that can be blocked by local anaesthetic. The nerve is accessed through the lateral wall of the vagina to produce anaesthesia to the perineal and anal skin. The nerve is formed by the anterior divisions of the ventral rami of the 2nd, 3rd and 4th sacral nerves. After its origin, it leaves the pelvis through the greater sciatic foramen to enter the gluteal region near the ischial spine. The nerve accompanies the internal pudendal vessels into the pudendal (Alcock’s) canal on the lateral wall of the ischiorectal fossa. In the posterior part of the canal it gives off its branches – inferior rectal nerve, the perineal nerve and the dorsal nerve of clitoris or penis. The common peroneal nerve is formed by L4, L5 and S1 and S2. The lumbosacral trunk is constituted by L4 and L5, and joins the sacral plexus. S4 contributes to the nerve supplying the levator ani and external anal sphincter. The obturator nerve arises from the lumbar plexus from the anterior divisions of L2, L3 and L4. None of these nerves is the target of the caudal block.

Answer 19

The S3 nerve root is responsible for the sensation of the sitting area of buttock. It is a constituent of the sacral plexus. The most important nerve arising from the sacral plexus is the sciatic nerve. It arises from L4, L5, S1, S2 and S3 roots of the sacral plexus. At its origin it is 2 cm wide and is the thickest nerve in the body. It enters the gluteal region from the pelvis through the greater sciatic foramen. At a variable level in the back of the thigh proximal to the popliteal fossa it divides into the common peroneal (fibular, L4, L5, S1, S2 and tibial, L4, L5, S1, S2, S3) nerves. The surface anatomy is an imaginary line drawn from the midpoint of the ischial tuberosity and greater trochanter to the apex of the popliteal fossa formed by the junction of the semimembranosus and semitendinosus medially and biceps femoris laterally. As an aid to remember the dermatome levels, we stand mainly on S1 (sole of foot), sit on S3 (buttocks) and wipe S4 (immediate perianal area). The commonest cause of damage to the sciatic nerve is iatrogenic misplaced gluteal injection. It may be affected in pelvic disease, severe hip trauma (7% of dislocations and 16% of fracture dislocations), or after total hip replacement (1%). Complete sciatic nerve palsy is rare and results in a flail foot and severe difficulty in walking. Because of its anatomical location in close proximity to the fibular head, the common peroneal nerve is the commonest nerve to be damaged in the lower limb. This results in a foot drop, high stepping gait and sensory loss over the lower lateral part of the leg and dorsum of the foot.

Answer 20

The symptoms described suggest that the obturator nerve is causing the pain. Here’s the reasoning: • Pain location and radiation: The obturator nerve supplies sensation to the inner thigh and knee area. • Pain relief by hip position: Bending the hip and rotating it outwards, which relieves the pain, indicates involvement of the obturator nerve. • Palpable lump: A palpable lump in this area could be associated with a hernia or other mass compressing the obturator nerve. Answer: E. Obturator The obturator nerve is causing this patient’s pain. She has the clinical features of an obturator hernia. The pain is referred to the knee by the geniculate branch of the obturator nerve (anterior divisions of L2, L3 and L4). The pain is much more pronounced in a strangulated hernia. Arising from the lumbar plexus, the obturator nerve lies on the psoas muscle and enters the obturator foramen. In the obturator canal it divides into anterior and posterior branches. In an obturator hernia, a swelling is not often palpable unless the hip is abducted, flexed and externally rotated. The hernia can sometimes be felt as a tender swelling on rectal or vaginal examination. Explanation: The obturator nerve provides sensory innervation to the medial aspect of the thigh. Pain along the inner thigh to the knee, which is relieved by specific hip movements, is characteristic of obturator nerve involvement. The palpable lump further suggests a mass effect on this nerve.

Answer 21

In the context of left ureteric colic with a stone impacted at the pelvic brim, the anatomical site where the stone is likely impacted is the common iliac artery bifurcation. Answer: A. Common iliac artery bifurcation Explanation: The ureter has several natural points of narrowing where stones are commonly impacted. One of these points is where the ureter crosses over the bifurcation of the common iliac artery at the pelvic brim. This anatomical feature makes it a common site for ureteral stones to become lodged, leading to ureteric colic symptoms. The stone is impacted at the bifurcation of the common iliac artery where it leaves the psoas muscle. This is one of the points of natural narrowing where a stone may get arrested. The other points of natural narrowing are: pelviureteric junction, where it is crossed by the vas deferens or broad ligament and at the ureterovesical junction. Knowledge of the relationships of the ureter is very important, so as to prevent iatrogenic damage. On the left it underlies the apex of the sigmoid mesocolon. It then runs over the external iliac artery and vein and then down the side wall of the pelvis in front of the internal iliac artery and behind the ovary. On the right it will be in close proximity to a pelvic appendix. Further distally at the level of the ischial spine it travels forwards and medially to enter the bladder base. Here the vas deferens in the male crosses above the ureter and in the female it crosses the lateral vaginal fornix.

Answer 22

During a hysterectomy with preservation of the ovaries, the ureters are particularly vulnerable to iatrogenic damage. Answer: D. Ureters Explanation: The ureters are at risk during a hysterectomy because they run close to the uterine arteries, which need to be ligated during the procedure. The ureters pass underneath the uterine arteries (“water under the bridge”) and are at risk of being inadvertently cut, clamped, or ligated. This is a well-known complication of gynecological surgeries, including hysterectomy.

Answer 23

Given the presentation of a perineal hematoma and blood at the external urinary meatus following a straddle injury, the anatomical structure most likely to be injured is the bulbar urethra. Answer: B. Bulbar urethra Explanation: A straddle injury often results in trauma to the bulbar (or bulbous) part of the urethra, which is located in the perineum. This part of the urethra is vulnerable to direct trauma when a person falls astride an object. The presence of blood at the external urinary meatus is a typical sign of urethral injury, and in this context, the bulbar urethra is the most commonly affected segment. This patient has injured his bulbar urethra (sometimes referred to as the anterior urethra) in the perineum. This injury involves the junction of the membranous with the bulbar portion of the urethra. The anatomy of this region is such that extravasation of urine occurs, unless recognition of the injury and treatment is carried out promptly. Urine leaks between the perineal membrane and the membranous layer of the perineal fascia (Colles’ fascia). As both these layers are firmly attached to the ischiopubic rami posteriorly, urine extravasates anteriorly into the loose connective tissue around the scrotum, penis and anterior abdominal wall. Should the posterior urethra be injured, urine leaks into the pelvic extraperitoneal tissues. Tear of the perineal membrane results in extravasation in the perineum. Anatomically, the membranous urethra is the shortest (1.5 cm) and least dilatable part of the male urethra (which is 18–20 cm long). The anterior urethra (16 cm) has a proximal perineal and a distal penile component. The posterior urethra is subdivided into preprostatic, prostatic and membranous parts. The female urethra is 4 cm long and 6 mm wide. Injury to the bladder neck, membranous and prostatic urethra can occur in fractures of the pelvis. Bladder rupture, extra- or intraperitoneal, is highly unlikely with such an injury. The clinical findings are not those of a bladder rupture.

Answer 24

The condition described, where the boy passes urine from a meatus on the underside of his glans penis, is indicative of glandular hypospadias. Answer: C. Glandular hypospadias Explanation: Hypospadias is a congenital condition where the urethral opening is located on the underside of the penis rather than at the tip. Glandular hypospadias specifically refers to the urethral opening being located on the underside of the glans penis, which matches the description provided. This is one of the more common and less severe forms of hypospadias.

Answer 25

Given the patient’s history of major pelvic fractures and bladder and urethral injuries, and his resulting complete incontinence after removal of the urethral catheter, it is most likely that the external urethral sphincter has been irreparably damaged. Answer: A. External urethral sphincter Explanation: The external urethral sphincter (also known as the sphincter urethrae) is a critical structure for voluntary control of urination. Damage to this sphincter, which can occur due to severe trauma or injury to the pelvic region, can result in loss of voluntary control over urination, leading to complete incontinence. The internal urethral sphincter contributes to continence but is primarily responsible for involuntary control, whereas the external sphincter is key for voluntary control, which aligns with the patient’s presentation of incontinence following catheter removal. This person’s urinary incontinence is due to damage to the external urethral sphincter. The internal urethral sphincter surrounding the proximal prostatic urethra is not responsible for urinary continence. This helps to prevent retrograde ejaculation by closing off the bladder neck during ejaculation. The urethral sphincter mechanism extends from the perineum through the urogenital hiatus into the pelvic cavity. The mechanism consists of the striated and smooth muscle of the urethra and the pubourethral part of levator ani; this surrounds the membranous urethra in the male. The fibres also reach up to the lowest part of the bladder neck. The muscles are of the slow twitch variety. The innervation is from the perineal branch of the pudendal nerve and the pelvic splanchnic nerves. All these nerves originate in the S2, S3 and S4 spinal segments. The urethral sphincter mechanism compresses the urethra when the bladder contains urine. It is located around the region of the highest urethral closing pressure, thus playing an important role in maintaining urinary continence. It relaxes during micturition and contracts to expel final drops of urine or semen from the bulbar urethra.

Answer 26

The structure that lies outside (outwith) the femoral sheath is the femoral nerve. Answer: D. Femoral nerve Explanation: The femoral sheath is a fascial compartment located in the upper part of the thigh, containing the femoral artery, femoral vein, and the femoral canal, which includes Cloquet’s (or Rosenmüller’s) node. The femoral nerve, however, lies outside the femoral sheath, laterally to these structures. Therefore, it is not enclosed within the femoral sheath.

Answer 27

The presence of a left-sided Trendelenburg gait with weakness of the ipsilateral hip abductors following a lateral approach total hip arthroplasty indicates injury to the superior gluteal nerve. Answer: E. Superior gluteal nerve Explanation: The superior gluteal nerve innervates the gluteus medius and gluteus minimus muscles, which are responsible for hip abduction. Damage to this nerve can result in weakness of these muscles, leading to a Trendelenburg gait, where the pelvis drops on the contralateral side when standing on the affected leg. This nerve is particularly susceptible to injury during surgical approaches to the hip, such as a lateral approach used in total hip arthroplasty.

Answer 28

The muscle that comprises the borders of the popliteal fossa and has an insertion on the head of the fibula is the biceps femoris. Answer: A. Biceps femoris Explanation: The biceps femoris muscle, which forms the superolateral boundary of the popliteal fossa, inserts on the head of the fibula. The other muscles mentioned do not insert on the head of the fibula: • Gastrocnemius: Inserts into the calcaneus via the Achilles tendon. • Plantaris: Also inserts into the calcaneus. • Semimembranosus: Inserts on the medial condyle of the tibia. • Semitendinosus: Inserts on the proximal tibia (pes anserinus).

Answer 29

The structure found within the lateral compartment of the leg is the superficial peroneal nerve. Answer: D. Superficial peroneal nerve Explanation: The lateral compartment of the leg contains the peroneus longus and peroneus brevis muscles, as well as the superficial peroneal nerve. The other structures listed are found in different compartments: • Anterior tibial artery: Found in the anterior compartment. • Deep peroneal nerve: Found in the anterior compartment. • Peroneus tertius: Found in the anterior compartment. • Tibialis anterior: Found in the anterior compartment. The superficial peroneal nerve supplies the muscles in the lateral compartment and provides sensation to the dorsum of the foot and the lower part of the leg.

Answer 30

The structure found anterior to the medial malleolus is the saphenous nerve. Answer: C. Saphenous nerve Explanation: The saphenous nerve is a branch of the femoral nerve and provides sensory innervation to the medial side of the leg and foot. It runs anterior to the medial malleolus, making it vulnerable during surgical procedures involving this area. The other structures listed are located posterior to the medial malleolus: • Flexor digitorum longus tendon • Posterior tibial artery • Tibial nerve • Tibialis posterior tendon These structures pass behind the medial malleolus in the tarsal tunnel.

Answer 31

The presentation of lumbar back pain, sciatica, numbness over the lateral border of the foot and ankle, and an absent ipsilateral ankle jerk is consistent with involvement of the S1 spinal nerve. Answer: C. S1 Explanation: The S1 spinal nerve provides sensory innervation to the lateral aspect of the foot and ankle. It also contributes to the Achilles (ankle) reflex. Compression or irritation of the S1 nerve root can lead to the symptoms described, including sciatica, numbness in the specified area, and a diminished or absent ankle jerk.

Answer 32

Given the patient’s history of atrial fibrillation and treatment to prevent complications of irregular heartbeat, the most likely cause of the excessive bleeding is a deficient prothrombin level in the blood, which can be due to the use of anticoagulant medications. Answer: B. Deficient prothrombin level in the blood Explanation: Patients with atrial fibrillation are commonly prescribed anticoagulants such as warfarin or direct oral anticoagulants (DOACs) to prevent thromboembolic complications like stroke. These medications work by inhibiting various components of the clotting cascade, leading to a reduction in prothrombin and other clotting factors. This inhibition can result in excessive bleeding, especially in the context of trauma. • Heparin deficiency (A) would not cause bleeding; in fact, heparin is an anticoagulant, and a deficiency would lead to increased clotting. • Excessive calcium levels (C) and excessive vitamin D levels (E) do not directly relate to coagulation in a way that would cause excessive bleeding in this context. • Excessive haematocrit (D) typically relates to thickened blood, not increased bleeding. Therefore, the most plausible cause in this scenario is a deficient prothrombin level due to anticoagulant therapy.

Answer 33

The most likely cause of the fall in core temperature during a prolonged open cholecystectomy is loss of homeostasis due to the anaesthetic. Answer: D. Loss of homeostasis due to the anaesthetic Explanation: Anesthesia disrupts the body’s normal thermoregulatory mechanisms, leading to a loss of homeostasis. This disruption can cause a significant drop in core temperature, known as perioperative hypothermia. Contributing factors include: • Vasodilation: Anesthetics cause vasodilation, which increases heat loss from the body surface. • Impaired thermoregulation: Anesthetics impair the body’s ability to regulate temperature effectively. • Exposure to a cool environment: The operating room is often kept cooler to maintain a sterile environment and for the comfort of the surgical team, even if the range provided (25–30°C) is not typically that cool. • Cool intravenous fluids and exposed internal organs: Even though fluids are administered at around 35°C, they can still contribute to heat loss, especially when internal organs are exposed during surgery. The other options are less likely causes of significant hypothermia in this context: • Reaction to propofol (A) typically does not cause a significant drop in core temperature. • Operating theatre temperature (B) in the range of 25–30°C would not normally cause a significant fall in core temperature unless combined with other factors. • Intravenous fluids at around 35°C (C) are usually warmed to help maintain body temperature. • Patients’ increased metabolic rate (E) would generate more heat, not less. Therefore, the most likely cause of the observed drop in core temperature is the loss of thermoregulatory homeostasis due to the effects of anesthesia.

Answer 34

The most likely cause of the fall in blood pressure on standing in this patient with diabetic autonomic neuropathy is impaired sympathetically-induced peripheral vasoconstriction. Answer: D. Impaired sympathetically-induced peripheral vasoconstriction Explanation: Orthostatic hypotension in diabetic patients is often due to autonomic neuropathy, which affects the body’s ability to regulate blood pressure upon standing. In a healthy individual, standing up triggers sympathetic nervous system activity that causes vasoconstriction, which helps maintain blood pressure. In patients with diabetic autonomic neuropathy, this sympathetic response is impaired, leading to insufficient vasoconstriction and a subsequent drop in blood pressure upon standing. The other options are less likely causes: • Excessive blood pressure homeostasis (A) would actually help maintain blood pressure, not cause a drop. • Excessive variability of his resting heart rate due to sinus arrhythmia (B) is unrelated to the drop in blood pressure on standing. • Excessive venoconstriction (C) would help maintain or even increase blood pressure, not cause it to drop. • Impairment of his renin-angiotensin system (E) could contribute to chronic hypotension but is less directly involved in the acute orthostatic response compared to sympathetic vasoconstriction. Therefore, the most plausible cause of the orthostatic hypotension in this context is the impaired sympathetically-induced peripheral vasoconstriction due to diabetic autonomic neuropathy.

Answer 35

The most likely cause of disseminated intravascular coagulation (DIC) leading to hypofibrinogenemia and a risk of excessive hemorrhage in a patient with multiple injuries is activation of the extrinsic clotting pathway by products of tissue damage. Answer: B. Activation of the extrinsic clotting pathway by products of tissue damage Explanation: Disseminated intravascular coagulation (DIC) is a complex condition characterized by widespread activation of the coagulation cascade, leading to the formation of blood clots throughout the body’s small vessels. This process consumes clotting factors and platelets, leading to a paradoxical risk of both thrombosis and bleeding. In the context of multiple injuries, the extrinsic clotting pathway is activated by tissue factor (TF), which is released from damaged tissues. This pathway is a primary mechanism by which DIC is initiated in trauma and other conditions involving significant tissue injury. • Activation of the extrinsic clotting pathway by a drug (A) is less likely as the cause in the context of trauma unless a specific drug known to induce DIC is involved. • Activation of the intrinsic clotting pathway by excess factor VIII levels (C) and by excess calcium ions (D) are not typical mechanisms leading to DIC in trauma patients. • Excess production of prothrombin (factor II) (E) does not typically cause DIC; rather, DIC involves the consumption of clotting factors, including prothrombin. Therefore, the most plausible cause of DIC in a trauma patient is the activation of the extrinsic clotting pathway by products of tissue damage.

Answer 36

Given the patient’s history of exposure to extremely cold temperatures and the resulting gangrenous changes in her legs, the most likely cause of this condition is core temperature maintained by peripheral vasoconstriction. Answer: C. Core temperature maintained by peripheral vasoconstriction Explanation: When the body is exposed to cold environments, it attempts to maintain core temperature by constricting blood vessels in the periphery (including the legs) to reduce heat loss. Prolonged and severe peripheral vasoconstriction in response to cold exposure can lead to reduced blood flow to the extremities, resulting in tissue ischemia and potentially gangrene. • Abnormal temperature-regulating centre in the basal ganglia (A) is unlikely to be the cause in this context, as the basal ganglia are not primarily involved in thermoregulation. • Cerebrally-induced hypothermia (B) is not a typical mechanism leading to gangrene in cold exposure scenarios. • Disorder of the autonomic nerves (D) could theoretically affect peripheral circulation, but the primary issue here is the body’s natural response to cold. • Leg skin temperature has been only 20–25°C (E) indicates a low temperature but does not directly explain the mechanism leading to gangrene. Therefore, the most plausible cause of the gangrenous changes in this patient’s legs is the peripheral vasoconstriction that occurred as her body attempted to maintain core temperature in extremely cold conditions.

Answer 37

In this scenario, the key difference between the two men—one with immersion hypothermia and the other with haematemesis—is likely the total forearm and hand blood flow. Answer: E. Total forearm and hand blood flow Explanation: Both men have cool peripheries and contracted superficial veins, which can be a response to peripheral vasoconstriction. However, the underlying causes of vasoconstriction are different: • Immersion hypothermia leads to vasoconstriction primarily to conserve core body heat. This response decreases blood flow to the periphery to minimize heat loss. • Haematemesis (vomiting blood) can lead to vasoconstriction due to blood loss and subsequent hypovolemic shock. This response aims to maintain blood pressure and ensure adequate perfusion to vital organs. While both conditions result in peripheral vasoconstriction, the total forearm and hand blood flow would likely differ due to the distinct underlying mechanisms. The hypothermic patient will have reduced blood flow due to the body’s attempt to conserve heat, whereas the patient with haematemesis may have reduced blood flow due to compensatory mechanisms in response to blood loss and hypovolemia. • The level of activity in peripheral sympathetic nerves (A) might be similar in both cases as vasoconstriction is generally mediated by sympathetic activity. • The part of the brain initiating vasoconstriction (B) is typically the hypothalamus for both thermal regulation and volume control. • Heat exchange between forearm arteries and venae commitantes (C) would not be significantly different as this is more of a passive process. • Peripheral catecholamine receptors (D) would likely respond similarly in both situations to sympathetic stimulation. Therefore, the most likely difference between the two men lies in the total forearm and hand blood flow, influenced by the different physiological stressors they are experiencing.

Answer 38

The condition described, characterized by severely excessive sweating in the hands, is most likely due to over-activity of cholinergic sympathetic nerves. Answer: C. Over-activity of cholinergic sympathetic nerves Explanation: Hyperhidrosis, particularly in the hands (palmar hyperhidrosis), is typically caused by an over-activity of the sympathetic nervous system. The sweat glands in the skin are primarily innervated by sympathetic nerves that release acetylcholine, a cholinergic neurotransmitter. This condition is not related to parasympathetic nerves, temperature-sensitive receptors in the hands, nor a deficiency in noradrenergic sympathetic activity. • Emotional instability (A) can exacerbate sweating but is not the primary cause of hyperhidrosis. • Over-activity of cholinergic parasympathetic nerves (B) is incorrect because sweat glands are innervated by the sympathetic nervous system. • Over-activity of temperature-sensitive receptors in her hands (D) does not directly cause hyperhidrosis; these receptors regulate responses to temperature, not sweating. • Under-activity of noradrenergic sympathetic nerves (E) would not cause excessive sweating; rather, it would reduce adrenergic responses. Thus, the most likely cause of her condition is the over-activity of cholinergic sympathetic nerves.

Answer 39

Given the symptoms of severe diarrhea, weight loss, profuse sweating, normal temperature, and an elevated pulse rate, the most likely diagnosis is primary thyrotoxicosis. Answer: D. Primary thyrotoxicosis Explanation: Primary thyrotoxicosis (hyperthyroidism) is a condition where there is excessive production of thyroid hormones. This can lead to symptoms such as weight loss, increased bowel movements (which can present as severe diarrhea), and increased sweating (hyperhidrosis). The elevated pulse rate (tachycardia) is also a common feature of hyperthyroidism. • Anxiety neurosis (A) could cause sweating and an elevated pulse, but it is less likely to explain the severe diarrhea and significant weight loss. • Hyperhidrosis (B) causes excessive sweating but does not account for the other symptoms like severe diarrhea and weight loss. • Inflammatory bowel disease (C) can cause severe diarrhea and weight loss but is less likely to cause profuse sweating and a rapid pulse without a fever. • Sepsis (E) could cause sweating and an elevated pulse, but it would typically also cause fever and other signs of systemic infection. Therefore, primary thyrotoxicosis is the most consistent diagnosis given the combination of symptoms.

Answer 40

The most likely diagnosis for the woman who suffers intermittently from cold white hands, particularly in cold weather, is intermittent vasospasm related to sympathetic nervous activity. Answer: D. Intermittent vasospasm related to sympathetic nervous activity Explanation: The symptoms described, including intermittent cold and white hands that improve with warming, are characteristic of Raynaud’s phenomenon. This condition involves episodic vasospasm of the arteries and arterioles in the extremities, usually triggered by cold or stress, leading to reduced blood flow. When the vasospasm resolves, the hands warm up and the skin temperature increases. The rise in pulse rate and blood pressure during the warming period suggests a systemic response to the cold and subsequent warming. • Bilateral arterial disease in the arms (A) would likely cause persistent symptoms rather than intermittent ones and might not improve significantly with warming. • Early heart failure (B) would typically present with other symptoms such as shortness of breath, fatigue, and fluid retention, rather than isolated intermittent cold hands. • Excessive and dangerous body warming (C) would generally cause symptoms of overheating, such as sweating, heat exhaustion, or even heat stroke, rather than an improvement in hand temperature. • Thyrotoxicosis (E) typically presents with symptoms like weight loss, heat intolerance, and palpitations, rather than intermittent cold hands. Therefore, the intermittent vasospasm related to sympathetic nervous activity (Raynaud’s phenomenon) is the most consistent diagnosis given the patient’s symptoms and response to warming.

Answer 41

Given the context of being exposed to mist, rain, wind, and low temperatures (about 5°C), the most likely cause of the young man’s condition (cold peripheries, exhaustion, but still rational) is hypothermia. Answer: D. Hypothermia Explanation: Hypothermia occurs when the body loses heat faster than it can produce it, leading to a drop in core body temperature. Symptoms of mild hypothermia include shivering, cold peripheries, exhaustion, and impaired physical and mental function, but the person can still be rational and answer questions. • Early stage of infection (A) might cause exhaustion and possibly fever or chills, but the environmental context makes hypothermia more likely. • Frostbite (B) affects localized areas exposed to cold and results in numbness and discoloration, but does not explain the generalized exhaustion and cold peripheries. • Hypoglycaemia (C) could cause confusion and cold sweat, but the primary context here involves prolonged exposure to cold weather, making hypothermia the more likely cause. • Ventricular fibrillation (E) is a life-threatening heart rhythm problem that would cause unconsciousness or severe distress, not rational responses. Therefore, hypothermia is the most plausible cause given the circumstances of exposure to cold weather and the symptoms described.

Answer 42

In the context of neurogenic shock due to a burst fracture of T10 with significant impingement of the spinal canal, the most important contributor to hypotension is increased venous capacitance. Answer: E. Increased venous capacitance Explanation: Neurogenic shock results from the disruption of the autonomic pathways in the spinal cord, leading to a loss of sympathetic tone. This causes widespread vasodilation and increased venous capacitance (i.e., pooling of blood in the venous system), resulting in hypotension despite adequate fluid resuscitation. Key factors in neurogenic shock include: • Decreased parasympathetic tone (A): Neurogenic shock is primarily due to the loss of sympathetic tone, not parasympathetic tone. • Decreased circulating volume (B): While hypovolemia can cause hypotension, the patient is described as having warm peripheries, which suggests vasodilation rather than hypovolemic shock. • Increased sympathetic tone (C): Neurogenic shock is characterized by decreased sympathetic tone, not increased. • Increased systemic vascular resistance (D): In neurogenic shock, systemic vascular resistance is decreased due to vasodilation. • Increased venous capacitance (E): The loss of sympathetic tone leads to venous pooling and increased capacitance, which reduces venous return to the heart and lowers cardiac output, resulting in hypotension. Therefore, the increased venous capacitance is the most critical factor contributing to the hypotension seen in neurogenic shock.

Answer 43

The most common postoperative cause of cardiogenic shock, especially in an elderly patient with a history of chest pain and dyspnea, is myocardial infarction. Answer: B. Myocardial infarction Explanation: Cardiogenic shock occurs when the heart is unable to pump enough blood to meet the body’s needs, often due to a significant impairment in cardiac function. In the postoperative setting, especially following major surgery such as a laparotomy, myocardial infarction (MI) is a leading cause of cardiogenic shock. The symptoms described—chest pain, dyspnea, hypotension, tachycardia, cool peripheries, and raised jugular venous pressure—are all consistent with cardiogenic shock due to an MI. • Hypovolemia (A) is a common cause of shock but leads to hypovolemic shock, not cardiogenic shock. This is characterized by low central venous pressure, unlike the raised JVP seen here. • Pericardial tamponade (C) can cause cardiogenic shock but is less common postoperatively unless there is a specific reason to suspect it, such as chest trauma or recent cardiac surgery. • Pulmonary embolus (D) is a possible cause of postoperative shock but typically presents with signs such as acute shortness of breath, pleuritic chest pain, and signs of right heart strain rather than the more global heart failure picture suggested by raised JVP. • Ventricular fibrillation (E) would typically result in immediate loss of consciousness and is less likely to be described in a scenario where the patient remains conscious and hypotensive with raised JVP. Therefore, myocardial infarction is the most likely cause of cardiogenic shock in this patient.

Answer 44

The most common cause of anaphylaxis under anaesthesia is muscle relaxants, e.g. suxamethonium. Answer: E. Muscle relaxants, e.g. suxamethonium Explanation: Anaphylaxis during anaesthesia is most frequently caused by muscle relaxants. These agents can trigger a severe allergic reaction, leading to symptoms such as tachycardia, hypotension, bronchospasm, and urticaria. Suxamethonium and other neuromuscular blocking agents are well-documented as common culprits for such reactions. • Antibiotics, e.g. co-amoxiclav (A): While antibiotics can cause anaphylaxis, they are less commonly the cause compared to muscle relaxants in the setting of anaesthesia. • Colloids, e.g. gelofusine (B): Colloids can cause anaphylaxis, but they are not the most common cause under anaesthesia. • Induction agent, e.g. thiopentone (C): Induction agents can cause allergic reactions, but they are also less commonly the cause compared to muscle relaxants. • Latex, e.g. surgical gloves (D): Latex allergy is a concern, especially in patients with a history of latex sensitivity, but muscle relaxants are more frequently implicated in anaphylactic reactions during anaesthesia. Therefore, muscle relaxants like suxamethonium are the most common cause of anaphylaxis in the anaesthetic setting.

Answer 45

The most appropriate initial management according to the Surviving Sepsis Resuscitation bundle is to consider vasopressors if hypotension does not respond to a minimum 20 mL/kg initial fluid resuscitation. Answer: C. Consider vasopressors if hypotension does not respond to minimum 20 mL/kg initial fluid resuscitation Explanation: The Surviving Sepsis Campaign guidelines recommend early identification and aggressive management of sepsis and septic shock, including: • Administer broad spectrum antibiotic within 24 hours of admission (A): Antibiotics should be administered much sooner, ideally within the first hour of recognizing sepsis. • Blood cultures are not essential if broad spectrum antibiotics are used (B): Blood cultures are essential and should be obtained before administering antibiotics, if this does not cause significant delay, to identify the causative organism. • Consider vasopressors if hypotension does not respond to minimum 20 mL/kg initial fluid resuscitation (C): This is correct. If the patient remains hypotensive after adequate fluid resuscitation, vasopressors should be considered to maintain adequate mean arterial pressure. • Maintain central venous pressure >12 mmHg (D): The current guidelines focus more on dynamic assessment of fluid responsiveness rather than static targets like central venous pressure. • Measure lactate on an arterial blood sample (E): Lactate measurement is essential, but it can be measured on either arterial or venous blood samples. Therefore, considering vasopressors if hypotension does not respond to an initial fluid resuscitation of at least 20 mL/kg is the most appropriate initial management step according to the Surviving Sepsis Resuscitation bundle.

Answer 46

The most accurate description of cardiac preload is end diastolic ventricular volume. Answer: B. End diastolic ventricular volume Explanation: Preload refers to the initial stretching of the cardiac myocytes prior to contraction, which is related to the volume of blood filling the ventricles at the end of diastole. This volume directly influences the cardiac muscle fibers’ length and tension before systole, determining the stroke volume and overall cardiac output according to the Frank-Starling law of the heart. • Central venous pressure (A) is often used as a surrogate measure of preload, but it is not a direct measurement of the actual volume in the ventricles. • Pulmonary artery occlusion pressure (C), also known as wedge pressure, is another surrogate that estimates left ventricular preload, but it is still an indirect measure. • Ventricular myocyte length (D) and ventricular myocyte tension (E) are related to the concept of preload, as they describe the physical properties of the cardiac muscle fibers, but they do not directly quantify the volume of blood in the ventricles. Therefore, the end diastolic ventricular volume most accurately describes cardiac preload.

Answer 47

The main determinant of coronary blood flow is the coronary artery diameter. Answer: C. Coronary artery diameter Explanation: Coronary blood flow is significantly influenced by the diameter of the coronary arteries. Any reduction in the diameter, such as from atherosclerotic plaque, spasm, or other factors, can critically reduce blood flow to the myocardium, leading to ischemia. The diameter of the coronary arteries can change in response to various stimuli, including metabolic demands, autoregulation, and endothelial function. • Autonomic nervous system (A): While it can influence heart rate and contractility, its direct impact on coronary blood flow is secondary to the effects on coronary artery diameter and myocardial oxygen demand. • Blood viscosity (B): It has an effect on blood flow, but it is not the primary determinant of coronary blood flow. • Diastolic blood pressure (D): Important for coronary perfusion pressure, especially during diastole, but it is still secondary to the impact of coronary artery diameter. • Myocardial oxygen demand (E): Increases in myocardial oxygen demand lead to compensatory increases in coronary blood flow, but this is mediated by changes in coronary artery diameter. Therefore, the main determinant of coronary blood flow in this context is the coronary artery diameter.

Answer 48

To increase cardiac output with the least impact on myocardial oxygen demand, preload should be optimized. Answer: D. Preload Explanation: Optimizing preload improves cardiac output by increasing the volume of blood returning to the heart, thereby enhancing ventricular filling and stroke volume according to the Frank-Starling mechanism. This approach increases cardiac output without significantly increasing myocardial oxygen demand, as it relies on the heart’s inherent ability to pump more effectively when more blood fills the ventricles. • Afterload (A): Decreasing afterload can improve cardiac output, but manipulating it often involves using vasodilators, which may have other systemic effects. Increasing afterload would increase myocardial oxygen demand. • Contractility (B): Enhancing contractility with inotropes increases cardiac output but also significantly raises myocardial oxygen demand. • Heart rate (C): Increasing heart rate can improve cardiac output, but it also significantly increases myocardial oxygen demand and may reduce diastolic filling time, which can be detrimental. • Serum calcium (E): While calcium is essential for muscle contraction, manipulating serum calcium levels to affect cardiac output is not a common or practical approach. Therefore, optimizing preload by ensuring adequate fluid status and venous return is the best approach to increase cardiac output with the least impact on myocardial oxygen demand.

Answer 49

The histopathology report indicating a large proportion of elastic tissue suggests that the tissue is most likely to originate from the aorta. Answer: A. Aorta Explanation: The aorta is characterized by a high content of elastic tissue, which allows it to withstand and dampen the pulsatile output of the heart. The elasticity of the aorta helps maintain continuous blood flow during diastole by allowing the vessel to stretch and recoil. This feature is more pronounced in the aorta than in other blood vessels. • Arteries (B): While arteries contain elastic tissue, the proportion is less than that found in the aorta. • Arterioles (C): Arterioles have less elastic tissue and more smooth muscle relative to their size. • Veins (D): Veins contain some elastic tissue, but it is much less than in the arteries and particularly the aorta. • Vena cava (E): The vena cava has some elastic tissue, but again, not as much as the aorta. Given the significant amount of elastic tissue described in the biopsy, the aorta is the most likely source.

Answer 50

Before the start of cardiopulmonary exercise testing, the organ that receives the greatest proportion of cardiac output is the liver. Answer: C. Liver Explanation: At rest, the liver receives the largest proportion of cardiac output compared to other organs. The liver is highly vascular and requires a substantial blood supply to perform its various metabolic, detoxification, and synthetic functions. • Brain (A): The brain receives a significant portion of cardiac output, approximately 15%, but this is less than what the liver receives. • Heart (B): The heart receives about 5% of the cardiac output, primarily to supply the myocardium via the coronary arteries. • Liver (C): The liver receives about 25-30% of the cardiac output, primarily through the hepatic artery and portal vein. • Kidneys (D): The kidneys receive around 20% of the cardiac output to facilitate filtration and urine formation. • Skeletal muscle (E): At rest, skeletal muscle receives a smaller proportion of cardiac output compared to the liver. However, during exercise, blood flow to skeletal muscles increases significantly. Therefore, before the start of the test, the liver receives the greatest proportion of cardiac output.

Answer 51

The adrenoreceptor that causes vasoconstriction when stimulated by adrenaline is the α1 receptor. Answer: A. α1 Explanation: Adrenaline (epinephrine) acts on various adrenergic receptors in the body, but vasoconstriction is primarily mediated by the stimulation of α1 receptors, which are located on the vascular smooth muscle cells. Activation of these receptors causes vasoconstriction, leading to an increase in vascular resistance and, consequently, blood pressure. This can be particularly useful in a peri-arrest situation to help maintain perfusion to vital organs. • α2 (B): These receptors are involved in feedback inhibition of norepinephrine release and have some vasoconstrictive effects, but their primary role is not direct vasoconstriction in response to adrenaline. • β1 (C): These receptors are primarily located in the heart and increase heart rate and contractility when stimulated by adrenaline. • β2 (D): These receptors cause vasodilation and bronchodilation when stimulated by adrenaline. • β3 (E): These receptors are involved in lipolysis and have a minimal role in vasoconstriction. Therefore, the α1 receptors are the primary receptors responsible for vasoconstriction by adrenaline.

Answer 52

The afferent nerve supply of the carotid baroreceptors is the glossopharyngeal nerve. Answer: A. Glossopharyngeal nerve Explanation: The carotid baroreceptors, located in the carotid sinus, play a crucial role in sensing changes in blood pressure. The afferent signals from these baroreceptors are carried by the glossopharyngeal nerve (cranial nerve IX) to the brainstem, where they help regulate cardiovascular responses to maintain blood pressure. • Glossopharyngeal nerve (A): The correct answer, as it carries afferent signals from the carotid baroreceptors. • Phrenic nerve (B): This nerve primarily innervates the diaphragm and is not involved in baroreceptor signaling. • Recurrent laryngeal nerve (C): A branch of the vagus nerve, it innervates the muscles of the larynx but is not involved in baroreceptor signaling. • Sympathetic chain (D): Involved in the autonomic regulation of various body functions, but it does not carry afferent signals from baroreceptors. • Vagus nerve (E): While the vagus nerve carries afferent signals from the aortic baroreceptors, it is the glossopharyngeal nerve that carries afferent signals from the carotid baroreceptors. Therefore, the glossopharyngeal nerve is responsible for transmitting the afferent signals from the carotid baroreceptors. The neurohumoral response to acute hypovolaemia is complex and can be divided into an early phase where maintenance of tissue perfusion is the priority and a later phase aimed at restoring a normal circulating volume. Carotid and aortic baroreceptors are stretch receptors that are stimulated by increased distention of the vessel. Following acute blood loss venous return decreases and due to the Frank–Starling mechanism blood pressure falls. Decreased intra-arterial pressure causes less vessel wall stretch and hence reduced activation of the baroreceptors. Afferent neurones from the carotid baroreceptors (also known as the carotid sinuses) travel in the glossopharyngeal nerves and from the aortic baroreceptors via the vagus. These afferent neurones synapse with cardiovascular control centres in the brainstem. Decreased firing of these afferent neurones will lead to inhibition of central parasympathetic outflow and increased central sympathetic outflow. Increased sympathetic outflow causes vasoconstriction and an increase in heart rate and myocardial contractility thereby maintaining perfusion to vital organs. Other components of the early phase include an increase in serum levels of antidiuretic hormone (ADH), causing retention of water and vasoconstriction (ADH is also known as vasopressin). The renin–angiotensin–aldosterone system (RAAS) is also activated causing vasoconstriction and sodium and water retention. Atrial natriuretic peptide secretion is inhibited and together with ADH and the RAAS this leads to restoration of circulating volume. Increased erythropoiesis returns haemoglobin levels to normal over a few weeks. The phrenic nerves supply motor function to the diaphragm and sensation to the mediastinal pleura and most of the diaphragm. The recurrent laryngeal nerve supplies the intrinsic muscles of the larynx (except cricothyroid) and sensation below the vocal cords.

Answer 53

In this scenario, the most likely cause for the delay in wound healing is the presence of a foreign body. Answer: B. Foreign body Explanation: Foreign bodies, such as the wood splinter mentioned, can significantly impede the wound healing process. They can cause persistent inflammation, infection, and mechanical irritation, all of which can delay healing. Removing the foreign body is essential to allow the wound to heal properly. • Diabetes mellitus (A): While diabetes can delay wound healing, there is no indication that the patient has diabetes. • Malnutrition (C): Malnutrition can affect wound healing, but there is no evidence provided that the patient is malnourished. • Site of wound (D): The location of the wound can influence healing, but it is less likely to be a primary factor compared to the presence of a foreign body. • Smoking (E): Smoking can impair wound healing due to its effects on blood flow and tissue oxygenation, but there is no information suggesting that the patient smokes. Therefore, the presence of the wood splinter (foreign body) is the most likely cause for the delay in wound healing in this case.

Answer 54

In the case of a postoperative wound infection presenting with signs of inflammation, yellowish discharge, and a high swinging pyrexia, the most appropriate initial management is to open the wound on the ward. Answer: B. Open the wound on the ward Explanation: Opening the wound on the ward allows for immediate drainage of any purulent material and helps relieve the infection. This step is essential for proper wound management and to control the infection locally. Once the wound is opened and drained, further steps such as wound culture, antibiotics, and other supportive measures can be considered based on the clinical findings. • CT scan of the abdomen (A): While imaging might be useful in certain scenarios to rule out deeper infections or abscesses, the initial step in managing a clearly infected surgical wound is to address the infection directly. • Re-exploration in the operating theatre (C): This is generally reserved for cases where there is suspicion of intra-abdominal complications that cannot be managed with simple drainage. • Start antibiotics (D): Antibiotics may be necessary, but they should be started after obtaining wound cultures and addressing the local infection through drainage. • Start intravenous fluids and antipyretics (E): These supportive measures can help manage symptoms but do not address the underlying source of infection. Therefore, opening the wound on the ward for drainage is the most appropriate initial management in this situation.

Answer 55

The wounds created for the ports during an elective laparoscopic cholecystectomy are best described as clean contaminated. Answer: B. Clean contaminated Explanation: Surgical wounds are classified based on their risk of infection: • Clean (A): These wounds are created under sterile conditions without entering the respiratory, alimentary, or genitourinary tracts. An example is a hernia repair. • Clean contaminated (B): These wounds involve controlled entry into the respiratory, alimentary, or genitourinary tracts under elective and controlled conditions without significant spillage or contamination. Laparoscopic cholecystectomy fits this category as it involves entering the biliary tract, which is a part of the alimentary system. • Contaminated (C): These wounds involve significant spillage from the gastrointestinal tract, major breaks in sterile technique, or traumatic wounds with non-purulent inflammation. • Dirty (D) and Dirty infected (E): These wounds involve existing infection or perforated viscera, often with purulent discharge. Therefore, the wounds created for the ports during a laparoscopic cholecystectomy are considered clean contaminated because the procedure involves controlled entry into the biliary tract.

Answer 56

The most likely histological abnormality associated with Barrett’s oesophagus in this patient is dysplasia. Answer: C. Dysplasia Explanation: Barrett’s oesophagus is a condition in which the normal squamous epithelium of the lower oesophagus is replaced by columnar epithelium, which is more typical of the intestinal lining. This process is known as metaplasia. However, the question specifies an “associated mucosal abnormality,” which is most likely referring to dysplasia in the context of Barrett’s oesophagus. Dysplasia represents a precancerous change and indicates abnormal epithelial cell growth and differentiation, which can progress to adenocarcinoma if not monitored and managed appropriately. • Accretionary growth (A): This term is not typically used in the context of Barrett’s oesophagus. • Differentiation (B): Differentiation refers to the process by which cells become specialized, but it is not specific to the abnormal changes seen in Barrett’s oesophagus. • Dysplasia (C): Dysplasia indicates abnormal cell growth and is a precancerous condition often seen in Barrett’s oesophagus. • Heterotopia (D): Heterotopia refers to the presence of normal tissue in an abnormal location, which is not the primary concern in Barrett’s oesophagus. • Metaplasia (E): Metaplasia is the initial change in Barrett’s oesophagus where the squamous epithelium is replaced by columnar epithelium. However, the “associated mucosal abnormality” likely refers to dysplasia rather than the initial metaplastic change. Therefore, dysplasia is the most likely associated mucosal abnormality in a patient with Barrett’s oesophagus.

Answer 57

In a patient presenting with haematuria and bilharzial nodules with papillomas, the most likely mucosal abnormality seen on histology would be a granuloma. Answer: B. Granuloma Explanation: Schistosomiasis (bilharzia) is caused by parasitic worms, and it is prevalent in North Africa. The presence of bilharzial nodules with papillomas in the bladder is indicative of chronic infection with Schistosoma haematobium. The body’s immune response to the eggs of the parasite often results in the formation of granulomas. These granulomas are characterized by collections of immune cells that form as the body attempts to wall off and contain the parasitic eggs. • Dysplasia (A): Dysplasia refers to abnormal growth and development of cells, which is a precancerous condition. However, it is not the typical response to schistosomiasis. • Granuloma (B): Granulomas are the characteristic histological finding in chronic schistosomiasis due to the immune response to the parasite’s eggs. • Metaplasia (C): Metaplasia refers to a change in the type of epithelium, which is not the primary feature in schistosomiasis. • Multiplicative growth (D): This term is not typically used in the context of schistosomiasis-related changes. • Pseudotubercles (E): Pseudotubercles are not a common finding in schistosomiasis. They are usually associated with other granulomatous diseases. Therefore, the most likely mucosal abnormality in this patient with bilharzial nodules and papillomas is the formation of granulomas.

Answer 58

In a patient with a long history of ulcerative colitis undergoing annual colonoscopic surveillance with random colonic biopsies, the pathologist is primarily looking for dysplasia. Answer: B. Dysplasia Explanation: Patients with long-standing ulcerative colitis are at an increased risk of developing colorectal cancer. Dysplasia refers to the presence of abnormal cells that have the potential to progress to cancer. Monitoring for dysplasia through regular surveillance biopsies is critical in managing these patients, as the detection of dysplasia can prompt early intervention to prevent progression to invasive carcinoma. • Auxetic growth (A): This term is not typically used in the context of pathological changes in ulcerative colitis. • Dysplasia (B): Dysplasia indicates abnormal, precancerous cell growth and is the primary concern in surveillance of patients with ulcerative colitis. • Hyperplasia (C): Hyperplasia refers to an increase in the number of normal cells, which is not specifically monitored in this context. • Metaplasia (D): Metaplasia refers to a change in cell type, which is not the main focus of surveillance in ulcerative colitis. • Regeneration (E): Regeneration refers to the repair and replacement of tissues, which is a normal process and not a pathological change looked for in this context. Therefore, the pathologist is looking for dysplasia in the random colonic biopsies taken during surveillance colonoscopies in this patient with long-standing ulcerative colitis.

Answer 59

The most likely diagnosis for a breast lump developing two weeks after a blunt injury to the breast is fat necrosis. Answer: E. Fat necrosis Explanation: Fat necrosis is a benign inflammatory response to trauma or surgery in the fatty tissue of the breast. It often presents as a lump, which can be tender and sometimes mimic malignancy, but it is non-cancerous. The history of trauma, such as a blunt injury from a road traffic accident, makes fat necrosis the most likely diagnosis in this scenario. • Apoptosis (A): Apoptosis is a programmed cell death process and does not typically result in a palpable lump. • Caseous necrosis (B): Caseous necrosis is associated with granulomatous infections like tuberculosis and is not typical in the context of trauma. • Coagulative necrosis (C): Coagulative necrosis is usually seen in ischemic injury to solid organs, such as the heart and kidneys, and not in the breast following trauma. • Colliquative necrosis (D): Also known as liquefactive necrosis, it is typically associated with brain tissue and abscess formation, not with trauma to the breast. Therefore, the presence of a breast lump following a blunt injury is most consistent with fat necrosis.

Answer 60

The role of the spleen that will be lost with its removal, which may affect the patient’s future health, is removal of encapsulated bacteria by phagocytic mechanisms. Answer: D. Removal of encapsulated bacteria by phagocytic mechanisms Explanation: The spleen plays a crucial role in the immune system, particularly in filtering blood and removing pathogens, including encapsulated bacteria (such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis) via its phagocytic cells. Splenectomy (removal of the spleen) significantly reduces the body’s ability to fight off these types of bacteria, increasing the risk of severe infections. This condition is known as overwhelming post-splenectomy infection (OPSI). • Deletion of immature autoreactive T cells (A): This function is primarily performed by the thymus, not the spleen. • Major site of insulin-producing cells (B): Insulin is produced by the pancreas, not the spleen. • Primary lymphoid organ where immature lymphocytes arise (C): The bone marrow and thymus are the primary lymphoid organs responsible for the generation and maturation of lymphocytes. • Responds to the pituitary gland to produce thyroxine (E): The thyroid gland produces thyroxine in response to signals from the pituitary gland, not the spleen. Therefore, the critical role lost with the removal of the spleen is its ability to remove encapsulated bacteria by phagocytic mechanisms, impacting the patient’s immune function and increasing the risk of infection.

Answer 61

The most likely effect of HIV infection on his immune response to infection is that activation of an effective adaptive immune response will be impaired. Answer: B. Activation of an effective adaptive immune response will be impaired Explanation: HIV (Human Immunodeficiency Virus) primarily targets CD4+ T cells, which are crucial for the activation and coordination of the adaptive immune response. The depletion of these cells leads to a weakened immune system, reducing the body’s ability to mount an effective response to infections and increasing susceptibility to opportunistic infections and certain cancers. • Ability to phagocytose and kill bacteria will be lost (A): HIV does not directly impair the function of phagocytes (such as macrophages and neutrophils) initially; however, over time, the overall immune dysfunction can indirectly affect phagocytic activity. • Activation of the alternative complement pathway will be prevented (C): The complement pathways, including the alternative pathway, are part of the innate immune system and are not directly affected by HIV infection. • None. HIV infection does not affect the immune response (D): This is incorrect; HIV significantly impairs the immune system, particularly the adaptive immune response. • Innate immune defences will be impaired (E): While HIV primarily affects the adaptive immune system, chronic HIV infection and the resultant immune dysfunction can indirectly impair innate immune responses over time. Therefore, the most significant effect of HIV infection is the impairment of the adaptive immune response, due to the depletion of CD4+ T cells.

Answer 62

Cytokines are small signalling proteins that regulate immune activation. Answer: C. Small signalling proteins that regulate immune activation Explanation: Cytokines are a broad category of small proteins that are important in cell signaling. They are secreted by various cells, particularly those of the immune system, and play crucial roles in regulating the immune response, inflammation, and hematopoiesis. In the context of septicaemia (sepsis), an uncontrolled release of pro-inflammatory cytokines can lead to systemic inflammation, acute respiratory distress syndrome (ARDS), and multiorgan failure. • Antigen-specific molecules produced by B lymphocytes (A): This describes antibodies, not cytokines. • Part of an enzyme cascade activated by immune complexes (B): This describes components of the complement system, not cytokines. • Subtype of cytotoxic T cells (D): This describes a type of T cell, not cytokines. • Ultracellular enzymes which kill bacteria within phagocytic cells (E): This describes lysosomal enzymes, not cytokines. Therefore, cytokines are the small signaling proteins that regulate immune activation and play a critical role in the immune response and inflammation.

Answer 63

The most likely mechanism causing autoimmune disease is that the body mounts an immune response against itself. Answer: A. Body mounts an immune response against itself Explanation: Autoimmune diseases occur when the body’s immune system mistakenly attacks its own tissues, recognizing them as foreign. This immune response can lead to chronic inflammation and progressive tissue damage, as seen in conditions like rheumatoid arthritis. • Chronic activation of allergen specific IgE sensitised mast cells initiates the disease (B): This describes the mechanism of allergic reactions, not autoimmune diseases. • Deficient immune response due to the action of an external agent (C): This could describe immunodeficiency, not autoimmunity. • Genetic defect causing a deranged immune response (D): While genetic factors can contribute to the development of autoimmune diseases, the primary mechanism is the immune system attacking self-tissues. • T cell activation is inhibited (E): This would describe a scenario of immunosuppression, not autoimmunity. Therefore, autoimmune diseases are primarily caused by the body mounting an immune response against its own tissues.

Answer 64

IgM antibodies are best described as short-lived antibodies produced during the early stages of ongoing infection. Answer: E. Short-lived antibodies produced during the early stages of ongoing infection Explanation: IgM is the first antibody isotype produced in response to an infection. It is effective at forming antigen-antibody complexes and is crucial in the initial stages of the immune response. IgM antibodies are typically short-lived and are later replaced by other isotypes such as IgG. • Antibodies that can survive on mucosal surfaces (A): This describes IgA antibodies, which are present in mucosal areas and secretions. • Antibodies which bind to mast cells during allergic reactions (B): This describes IgE antibodies, which play a role in allergic responses. • Antibodies which can confer protection to newborn infants (C): This describes IgG antibodies, which can cross the placenta and provide passive immunity to the fetus. • Long-lived antibodies that provide long-term protection against infection (D): This describes IgG antibodies, which are responsible for long-term immunity. Therefore, IgM antibodies are short-lived antibodies produced during the early stages of an ongoing infection.

Answer 65

The Heaf test, also known as the Mantoux test or tuberculin skin test (TST), is used to determine whether a person has been exposed to the bacterium Mycobacterium tuberculosis, which causes tuberculosis (TB). The test involves injecting a small amount of tuberculin purified protein derivative (PPD) into the skin and observing the reaction. Given this information, the most likely immunological significance of a positive Heaf test result is: C. Determines T cell responses to the tubercle bacillus A positive reaction indicates that the person’s immune system has been exposed to TB bacteria and has mounted a T cell-mediated immune response. This does not necessarily mean the person has active tuberculosis, but it does suggest that they have been infected with the bacteria at some point. Further tests would be needed to determine if there is an active infection.

Answer 66

The concept of “immune privilege” refers to certain sites in the body where immune responses are limited or regulated to prevent damage to delicate tissues. The anterior chamber of the eye is one such site. This privilege helps to protect the eye from inflammatory damage that could impair vision. Given this context, the most likely immunological mechanism involved in why the woman will not require immunosuppressive therapy after a corneal graft is: C. Beneficial responses are promoted while damaging ones are suppressed. This mechanism explains how the eye can tolerate foreign tissue, such as a corneal graft, without initiating a damaging immune response. In immune-privileged sites, the immune system is selectively regulated to allow tolerance of antigens without causing harmful inflammation.

Answer 67

Given the details provided: • Haemoglobin of 105 g/L, which indicates anemia (normal range for women is typically 120-160 g/L). • Mean cell volume (MCV) is low, indicating microcytosis. • Red blood cells are pale, suggesting hypochromia. • The patient has a history of heavy menstrual bleeding, which can lead to iron deficiency. • She has been on oral iron preparations intermittently, suggesting she has been treated for iron deficiency. The most likely diagnosis is: D. Microcytic anaemia due to iron deficiency Iron deficiency anemia is characterized by low hemoglobin levels, low MCV (microcytosis), and hypochromic red blood cells. This is consistent with the patient’s history of heavy menstrual bleeding and intermittent iron supplementation.

Answer 68

Given the details provided: • The patient is anemic with a hemoglobin level of 105 g/L. • The mean red cell volume (MCV) is above the normal range, indicating macrocytosis. • The reticulocyte count is around the lower limit of normal. The most likely diagnosis is: B. Macrocytic anaemia due to deficiency of vitamin B12 Macrocytic anemia is often caused by deficiencies in vitamin B12 or folate. Given the patient’s age and the gradually increasing tiredness, a deficiency in vitamin B12 is a likely cause. This type of anemia is characterized by larger than normal red blood cells and can be accompanied by neurological symptoms if left untreated.

Answer 69

Given the patient’s clinical scenario: • The patient has chronic renal failure and is undergoing peritoneal dialysis. • His hemoglobin level is 105 g/L, indicating anemia. • His mean cell volume (MCV) is normal, and red cells look normal microscopically, suggesting normocytic anemia. In chronic renal failure, anemia is commonly caused by a deficiency in erythropoietin, a hormone produced by the kidneys that stimulates red blood cell production in the bone marrow. The most effective treatment for anemia in patients with chronic renal failure is: A. Erythropoietin to stimulate his bone marrow Explanation: 1. Erythropoietin Deficiency: In chronic renal failure, the kidneys fail to produce adequate amounts of erythropoietin, leading to reduced red blood cell production and anemia. 2. Effective Treatment: Administering erythropoietin directly addresses the primary cause of anemia in these patients. It stimulates the bone marrow to produce more red blood cells. 3. Other Options: While iron and vitamin B12 can be beneficial if deficiencies exist, they are not the primary issue in this scenario. Regular transfusions are not the first-line treatment due to risks such as iron overload and alloimmunization. Thus, erythropoietin is the most effective and appropriate management for anemia in a patient with chronic renal failure undergoing peritoneal dialysis.

Answer 70

The 6-year-old girl with cyanotic heart disease and central cyanosis has a hemoglobin level of 165 g/L, indicating polycythemia. Given the context of cyanotic heart disease, the most likely cause of her polycythemia is: E. Increased circulating erythropoietin Explanation: 1. Cyanotic Heart Disease: Cyanotic heart disease leads to chronic hypoxia, as the body is not receiving enough oxygen due to the heart’s inability to properly oxygenate the blood. 2. Erythropoietin Response: The kidneys respond to chronic hypoxia by increasing the production of erythropoietin, a hormone that stimulates red blood cell production in the bone marrow. 3. Polycythemia: Increased levels of erythropoietin lead to increased red blood cell production, resulting in polycythemia, which is a compensatory mechanism to improve oxygen delivery to tissues. Incorrect Options: • A. Decreased circulating erythropoietin: This would lead to anemia, not polycythemia. • B. Direct stimulation of her red bone marrow by hypoxia: While hypoxia stimulates erythropoietin production, it is the increased erythropoietin that directly stimulates the bone marrow. • C. Direct stimulation of her red bone marrow by a raised carbon dioxide level: Elevated CO2 levels do not directly stimulate the bone marrow. It is the hypoxia that triggers erythropoietin production. • D. Frequent blood transfusions: This could cause polycythemia, but there is no indication in the scenario that the child is receiving frequent transfusions. Thus, the increased circulating erythropoietin due to chronic hypoxia from cyanotic heart disease is the most likely cause of her polycythemia.

Answer 71

Given the context of a 60-year-old man undergoing chemotherapy for non-Hodgkin lymphoma who has developed a painful throat with irregular ulceration on his pharynx, the most likely cause of his throat problem is: A. Acute depression of bone marrow function Explanation: 1. Chemotherapy Side Effects: Chemotherapy for non-Hodgkin lymphoma can cause myelosuppression, which is a significant reduction in bone marrow activity. This results in decreased production of white blood cells, red blood cells, and platelets. 2. Neutropenia and Infections: The reduction in white blood cells, particularly neutrophils, can lead to neutropenia, making the patient highly susceptible to infections, including those in the oral and pharyngeal regions. 3. Mucosal Damage: Chemotherapy can also cause direct damage to the mucosal lining of the mouth and throat, leading to mucositis, which presents as painful ulcerations and inflammation. Incorrect Options: • B. Acute lymphatic leukemia: This is a different condition and not directly related to the patient’s current chemotherapy for non-Hodgkin lymphoma. • C. Exacerbation of chronic myeloid leukemia: This is another unrelated condition and would not be a typical consequence of chemotherapy for non-Hodgkin lymphoma. • D. Throat infection with Clostridium difficile organisms: C. difficile primarily causes gastrointestinal infections, particularly colitis, not throat infections. • E. Throat infection with MRSA organisms: While possible, MRSA infections typically occur in hospitalized patients or those with invasive devices. The description suggests a more general immune suppression and susceptibility to infections due to chemotherapy. Therefore, the most likely cause of his throat problem is the acute depression of bone marrow function resulting from his chemotherapy regimen.

Answer 72

Given the context of a 27-year-old man with extensive and persistent blood loss from superficial cuts and abrasions, the most likely cause of this excessive bleeding is: D. His factor VIII level is about 20% of the normal average Explanation: 1. Factor VIII Deficiency (Hemophilia A): A significantly reduced level of factor VIII (about 20% of the normal average) suggests a moderate form of Hemophilia A. Hemophilia A is a genetic disorder that impairs the body’s ability to make blood clots, leading to prolonged bleeding from even minor injuries. 2. Excessive and Persistent Bleeding: This level of factor VIII deficiency would result in more extensive and prolonged bleeding from superficial cuts and abrasions than would normally be expected. Incorrect Options: • A. He completed, two weeks previously, a course of low molecular weight heparin to prevent deep venous thrombosis: The effects of low molecular weight heparin typically do not persist for two weeks after cessation of therapy. • B. He is on warfarin treatment and his INR is 1.2: An INR of 1.2 is within the normal range (therapeutic range for warfarin treatment is typically 2-3), suggesting no significant anticoagulation effect. • C. He is on warfarin treatment and his INR is 0.8: An INR of 0.8 is below the normal range, indicating that his blood is more prone to clotting rather than excessive bleeding. • E. His platelet count is slightly below the lower limit of the normal range: A slightly low platelet count would not usually cause extensive and persistent bleeding from superficial cuts and abrasions. Severe thrombocytopenia (very low platelet count) would be required to cause such symptoms. Therefore, a significantly low factor VIII level is the most likely cause of his excessive bleeding.

Answer 73

Total parenteral nutrition (TPN) should provide a balanced mix of carbohydrates, proteins, and fats to meet the energy and nutrient requirements of a patient. The most appropriate management to meet the 24-hour energy requirements for a 50-year-old woman requiring total parenteral feeding would be: B. 20% dextrose and 10% lipid Explanation: 1. Balanced Nutrient Supply: Total parenteral nutrition should include a balanced combination of macronutrients (carbohydrates, proteins, and fats) to adequately meet the patient’s energy needs and maintain metabolic balance. 2. Energy Density: A combination of 20% dextrose and 10% lipid provides a substantial amount of energy. Dextrose (glucose) is a primary source of carbohydrate energy, while lipids provide a dense source of calories and essential fatty acids. 3. Amino Acids: While not explicitly mentioned in option B, TPN typically also includes amino acids to meet the protein needs of the patient. It’s essential to include amino acids in TPN to prevent muscle wasting and promote tissue repair. Incorrect Options: • A. 5% dextrose and 10% amino acid solution: This combination may not provide sufficient energy because 5% dextrose is a low concentration for carbohydrate energy, and amino acids are primarily for protein needs, not energy. • C. 5% dextrose as the sole provider of energy: This would not provide sufficient energy and lacks essential proteins and fats, leading to nutritional deficiencies. • D. 50% dextrose as the sole provider of energy: This would provide a high carbohydrate load, which could cause hyperglycemia and other metabolic complications. It also lacks proteins and fats. • E. 20% lipid as the sole provider of energy: Lipids alone cannot meet all nutritional requirements and may lead to complications if used as the sole energy source, such as essential fatty acid deficiency and insufficient carbohydrate and protein intake. Therefore, the combination of 20% dextrose and 10% lipid is the most appropriate choice for meeting the 24-hour energy requirements of a patient requiring total parenteral feeding.

Answer 74

The most likely cause of the spasm in a 60-year-old man with a long history of duodenal ulcer, presenting with gastric outlet obstruction and Chvostek’s sign, is: C. Alkalotic tetany from metabolic alkalosis Explanation: 1. Gastric Outlet Obstruction: This condition leads to incessant vomiting, which results in the loss of gastric acid (hydrochloric acid). 2. Metabolic Alkalosis: The loss of gastric acid through vomiting results in a decrease in hydrogen ions and an increase in bicarbonate ions, leading to metabolic alkalosis. 3. Chvostek’s Sign: This is a clinical sign of hypocalcemia, which can be a result of metabolic alkalosis. In alkalosis, the ionized calcium levels in the blood decrease because calcium binds more to albumin when the pH is high, leading to symptoms like muscle spasms and tetany. 4. Non-bilious Vomiting: Since the vomiting is non-bilious (does not contain bile), it suggests that the obstruction is above the level where bile enters the gastrointestinal tract (i.e., proximal to the duodenum). Incorrect Options: • A. Acidotic tetany from respiratory acidosis: Respiratory acidosis results from hypoventilation and an increase in CO2 levels, leading to acidemia. This does not fit the clinical scenario of incessant vomiting. • B. Acidotic tetany from respiratory alkalosis: Respiratory alkalosis results from hyperventilation and a decrease in CO2 levels. It can cause tetany, but it does not match the clinical context of gastric outlet obstruction. • D. Alkalotic tetany from respiratory acidosis: This is a contradictory statement, as respiratory acidosis is an acidotic condition, not alkalotic. • E. Alkalotic tetany from respiratory alkalosis: Respiratory alkalosis is not related to vomiting and gastric outlet obstruction, which clearly indicate a gastrointestinal cause. Therefore, the patient’s spasm is most likely due to alkalotic tetany from metabolic alkalosis, resulting from the loss of gastric acid due to incessant vomiting caused by gastric outlet obstruction.

Answer 75

The most likely cause of the acidosis in a 25-year-old woman with poorly managed type 1 diabetes who presents with diabetic ketoacidosis and a high anion gap acidosis is: A. A decrease in bicarbonate concentration Explanation: 1. Diabetic Ketoacidosis (DKA): In DKA, the body breaks down fats into ketones due to the lack of insulin, leading to the accumulation of acidic ketone bodies in the blood, which causes metabolic acidosis. 2. High Anion Gap Acidosis: This is characterized by an increase in unmeasured anions (such as ketones) in the blood, leading to a high anion gap. The anion gap is calculated as [Na+] - ([Cl-] + [HCO3-]). 3. Decrease in Bicarbonate: The accumulation of ketones in DKA leads to a buffering response that consumes bicarbonate, resulting in a decreased bicarbonate concentration, which is a primary cause of the high anion gap acidosis seen in DKA. Incorrect Options: • B. A decrease in chloride concentration: A decrease in chloride concentration would not directly cause a high anion gap acidosis. Chloride levels may decrease in some forms of metabolic alkalosis but are not the primary factor in DKA. • C. An increase in potassium concentration: While hyperkalemia can be seen in DKA due to shifts of potassium from cells to the blood, it is not the primary cause of the acidosis. • D. An increase in sodium concentration: An increase in sodium concentration does not cause acidosis and is not typically seen in DKA. • E. Combined increase in sodium and decrease in chloride: This scenario does not describe the pathophysiology of DKA and would not explain the high anion gap acidosis. Therefore, the acidosis in this patient with diabetic ketoacidosis is most likely caused by a decrease in bicarbonate concentration.

Answer 76

Correct answer: B) Abductor pollicis longus tendon Explanation: The thenar eminence is a muscular prominence on the palmar surface of the hand, primarily composed of thumb muscles. The abductor pollicis longus tendon is prone to tenosynovitis or tendonitis, leading to pain and swelling in this area, commonly known as de Quervain's tenosynovitis. Additional Information De Quervain's tenosynovitis affects the tendons on the thumb side of your wrist. Symptoms include pain and tenderness, especially when forming a fist, grasping or turning the wrist. Treatment options range from physical therapy and injections to surgery.

Answer 77

Correct answer: D) All of the above Explanation: Preventing surgical site infections requires a multifaceted approach. While preoperative skin scrub with antibacterial soap (A) reduces skin flora, it's just one aspect. Proper hand hygiene and double gloving (B) minimize transmission from surgical staff. Maintaining patient normothermia (C) reduces infection risk by promoting immune function, blood flow and oxygen delivery to tissues. Additional measures include: Antibiotic prophylaxis Sterile equipment and supplies Surgical technique and tissue handling Postoperative wound care

Answer 78

Correct answer: B) Non-Hodgkin lymphoma (follicular) Explanation: Follicular lymphoma, a type of non-Hodgkin lymphoma (NHL), typically presents with painless lymphadenopathy (enlarged lymph nodes). Histopathology shows lymphoid follicles with germinal centers, characteristic of follicular lymphoma. Key features: Indolent course: Slow growth, often asymptomatic. Follicular architecture: Germinal centers surrounded by mantle zones. Immunohistochemistry: CD20+, CD10+, BCL2+. Differential diagnoses: Reactive lymphadenopathy (C): Typically resolves, lacks follicular pattern. Hodgkin lymphoma (A): Presence of Reed-Sternberg cells. Papillary thyroid carcinoma (D): Characteristic nuclear features, different clinical context.

Answer 79

Correct answer: B) Closed reduction under sedation Explanation: Initial management for a closed distal radius fracture with dorsal angulation involves closed reduction to restore anatomical alignment, minimize complications and improve outcomes. Steps for closed reduction: Analgesia and sedation: Ensure patient comfort. Assistant: Maintain traction. Reduction maneuver: Apply gentle pressure to fracture fragments. Post-reduction imaging: Confirm alignment. Immobilization: Cast or splint application. Indications for open reduction and internal fixation (ORIF) (Option A): Unstable fractures Failed closed reduction Articular involvement Neurovascular compromise Other options: Application of a plaster cast (C): Suitable after successful closed reduction. Traction and manipulation under anesthesia (D): Typically reserved for complex or unstable fractures.

Answer 80

Answer and Explanation Correct answer: A) Patient's autonomy and informed decision Explanation: Surgical consent prioritizes respecting patients' autonomy, ensuring they make informed decisions. Key elements: Capacity: Patients must understand implications. Voluntariness: Free from coercion. Information: Clear explanation of risks, benefits and alternatives. Comprehension: Patients understand provided information. Additional Principles Respecting patient autonomy and dignity Ensuring informed consent for all procedures Documenting consent accurately Considering cultural, linguistic and cognitive factors Relevance to Surgical Practice Informed consent promotes trust, accountability and patient-centered care. Breaches can lead to medico-legal consequences.

Answer 81

Correct answer: A) Common bile duct Explanation: Calot's triangle, bounded by the liver edge, cystic duct and common hepatic duct, contains crucial structures. The common bile duct (CBD) is most vulnerable during dissection due to: Anatomical variability: CBD location and course. Proximity to cystic duct: Risk of misidentification. Inflammation or fibrosis: Obscured anatomy. Consequences of CBD injury: Bile leakage: Peritonitis, abscesses. Stricture formation: Cholestasis, jaundice. Long-term complications: Liver damage, cirrhosis. Prevention strategies: Clear identification: Confirm anatomy. Careful dissection: Minimize tissue damage. Intraoperative cholangiography: Visualize bile ducts.

Answer 82

Correct answer: A) Endovascular angioplasty and stenting Explanation: Endovascular intervention is the preferred initial management for intermittent claudication due to superficial femoral artery stenosis. Rationale Minimally invasive: Reduces recovery time and complications. Effective symptom relief: Improves walking distance. Low risk: Compared to open surgery. Indications for Endovascular Intervention Symptomatic stenosis: Intermittent claudication, critical limb ischemia. Lesion characteristics: Short-segment stenosis, non-calcified. Patient factors: Comorbidities, high surgical risk. Alternative Options Medical therapy (C): Best for mild symptoms or non-revascularizable patients. Surgical bypass (B): Reserved for complex lesions, failed endovascular treatment or severe ischemia. Thrombolysis (D): Suitable for acute limb ischemia. Additional Considerations Lifestyle modifications: Smoking cessation, exercise and healthy diet. Pharmacological management: Antiplatelets, statins, ACE inhibitors. Regular follow-up: Monitor disease progression, intervention effectiveness.

Answer 83

Correct answer: B) Posterior cervical laminectomy Explanation: For spinal cord tumors at C5-C6, posterior cervical laminectomy is often preferred. Rationale Direct access: Posterior approach provides straightforward access to spinal cord tumors. Minimal disruption: Preserves anterior spinal stability. Effective decompression: Relieves spinal cord compression. Indications Intraspinal tumors: Meningiomas, neurofibromas, schwannomas. Spinal cord compression: Symptomatic cord impingement. Posterior or lateral tumor location: Optimizes surgical exposure. Considerations Tumor histology: Influences surgical strategy. Spinal stability: May require fusion. Neurological status: Guides surgical urgency. Alternative Options Anterior cervical discectomy and fusion (ACDF) (A): Suitable for anteriorly located tumors or cervical disc disease. Posterolateral approach (costotransversectomy) (C): Ideal for thoracic spine tumors. Transoral odontoidectomy (D): Reserved for high cervical or odontoid tumors.

Answer 84

Answer and Explanation Correct answer: B) Air enema reduction under fluoroscopy Explanation: For pediatric intussusception, air enema reduction under fluoroscopy is the preferred initial management. Rationale High success rate: 80-90% reduction success. Minimally invasive: Avoids surgery. Quick recovery: Reduces hospital stay. Indications Symptomatic intussusception: Abdominal pain, vomiting, bloody stools. Diagnostic confirmation: Ultrasound or CT scan. Stable patient: No signs of shock, peritonitis or free fluid. Contraindications Shock or instability: Requires surgical intervention. Perforation or peritonitis: Surgical emergency. Failed reduction: Requires surgical exploration. Additional Considerations Monitoring: Post-reduction observation for recurrence or complications. Surgical backup: Preparedness for emergency laparotomy. Investigation for lead point: Evaluate for underlying conditions (e.g., Meckel's diverticulum).

Answer 85

Correct answer: B) Core needle biopsy (CNB) Explanation: Core needle biopsy (CNB) is the preferred diagnostic method for palpable breast lesions with a BI-RADS 4 classification. Rationale Tissue sampling: Provides histological diagnosis. Accuracy: Higher than fine-needle aspiration cytology (FNAC). Guides management: Informs treatment decisions. Indications Palpable lesions: Confirming diagnosis before surgery. Imaging abnormalities: BI-RADS 4 or 5 lesions. Preoperative diagnosis: Essential for breast cancer management. Advantages Over Other Options FNAC (A): Lower accuracy, limited tissue sampling. Excisional biopsy (C): More invasive, often unnecessary. Mammography-guided vacuum-assisted biopsy (D): Suitable for non-palpable, image-detected lesions. Additional Considerations Multidisciplinary team discussion: Radiologist, pathologist and surgeon collaboration. Genetic testing: Consider for high-risk patients. Preoperative axillary staging: Evaluate lymph node involvement.

Answer 86

Correct Answer C) Urinary tract infection (UTI) Explanation Urinary tract infections (UTIs) are characterized by: Dysuria: Painful urination Frequency: Frequent voiding Urgency: Sudden need to urinate Hematuria: Blood in urine (microscopic or gross) Leukocyte esterase: Positive test indicating white blood cells Additional Considerations Urinalysis confirmation: Verify infection. Antibiotic therapy: Treat bacterial UTIs. Further evaluation: Consider imaging or urology referral for recurrent or complex infections. Other Options Bladder cancer (B): Typically presents with gross hematuria. Benign prostatic hyperplasia (D): Causes obstructive symptoms without infection signs.

Answer 87

Correct answer: D) All of the above Explanation: Postoperative left ventricular dysfunction after CABG requires multifaceted management. Initial Support Inotropic support (A): Enhance contractility, maintain perfusion. Vasopressors: Support blood pressure. Advanced Therapies Mechanical circulatory support (B): Consider intra-aortic balloon pump (IABP), extracorporeal membrane oxygenation (ECMO) or ventricular assist devices (VADs). Heart transplantation evaluation (C): For severe, irreversible dysfunction. Additional Measures Optimize volume status: Ensure adequate filling pressures. Electrolyte and acid-base balance: Correct abnormalities. Reduce afterload: Vasodilators or ACE inhibitors. Anti-arrhythmic prophylaxis: Prevent arrhythmias. Early mobilization and rehabilitation: Enhance recovery. Timing and Teamwork Early intervention: Prevents further decline. Multidisciplinary team: Collaborate with cardiologists, intensivists and surgeons.

Answer 88

Correct Answer A) Aneurysmal rupture Explanation Aneurysmal rupture is the most common cause (80-90%) of spontaneous subarachnoid hemorrhage. Characteristics Sudden, severe headache: "Thunderclap headache" Vomiting and altered consciousness: Indicates increased intracranial pressure Subarachnoid hemorrhage on CT: Blood in cerebrospinal fluid spaces Risk Factors Hypertension: Accelerates aneurysm formation Family history: First-degree relatives Smoking: Increases rupture risk Immediate Actions Stabilization: Secure airway, breathing and circulation Neurosurgical consultation: Consider clipping or coiling Monitoring: Watch for vasospasm, hydrocephalus and rebleeding Other Options Arteriovenous malformation (B): Less common, often congenital. Hypertensive hemorrhage (C): Typically intraparenchymal, not subarachnoid. Traumatic brain injury (D): History of trauma, different imaging findings.

Answer 89

Correct answer: A) Zollinger-Ellison syndrome Explanation Zollinger-Ellison syndrome (ZES) is characterized by: Multiple duodenal ulcers: Unusual locations, large or recurrent. Severe abdominal pain: Epigastric, radiating to back. Diarrhea: Gastric acid hypersecretion. Weight loss: Malabsorption. Diagnostic Features Elevated gastrin levels: Fasting gastrin >1000 pg/mL. Gastric acid hypersecretion: Basal acid output increased. Endoscopic findings: Multiple, large or atypical ulcers. Management Proton pump inhibitors (PPIs): Control acid secretion. Surgical resection: Gastrinoma localization and removal. Somatostatin analogs: Octreotide for symptom control. Differential Diagnosis Peptic ulcer disease (B): Typically single, benign ulcers. Crohn's disease (C): Inflammation, skip lesions, and fistulae. Giardiasis (D): Parasitic infection causing diarrhea. Key Considerations Gastrinoma localization: Imaging studies (CT, MRI, PET). Multiple endocrine neoplasia type 1 (MEN1): Association with ZES. Long-term follow-up: Monitoring for recurrence, metastasis.

Answer 90

Correct answer: A) Anterior cruciate ligament (ACL) tear Explanation ACL tears typically result from twisting injuries, sudden stops or deceleration. Diagnostic Features Positive Lachman test: Excessive anterior tibial translation. Anterior drawer test: Abnormal tibial movement. Pivot shift test: Abnormal knee movement. Knee instability: Giving way or buckling. MRI confirmation: Definitive diagnosis. Mechanism of Injury Non-contact injuries: Sudden changes in direction. Landing from jumps: Incorrect landing technique. Deceleration: Quick reductions in speed. Treatment Options Conservative management: Rehabilitation for partial tears or low-activity patients. Surgical reconstruction: ACL reconstruction for active patients or complete tears. Physical therapy: Strengthening surrounding muscles. Differential Diagnosis Posterior cruciate ligament (PCL) tear (B): Posterior instability. Medial collateral ligament (MCL) tear (C): Medial knee pain. Meniscal tear (D): Joint line pain, locking or catching. Key Considerations Early diagnosis: Prevents secondary injuries. Individualized treatment: Activity level, tear severity. Rehabilitation focus: Strength, proprioception and agility.

Answer 91

Correct answer: D) All of the above Preoperative Evaluation for Tonsillectomy Complete Blood Count (CBC) (A): Assess for anemia, infection or bleeding disorders. Bleeding Disorders Screening (B): Identify coagulopathy, von Willebrand disease or platelet dysfunction. Liver Function Tests (LFTs) (C): Evaluate liver status, affecting metabolism of anesthetics and medications. Additional Preoperative Considerations: Medical history: Review for diabetes, hypertension or respiratory issues. Allergy history: Document antibiotic allergies. Current medications: Note anticoagulants, antiplatelets or immunosuppressants. Physical examination: Assess airway, neck mobility and overall health. Informed consent: Discuss risks, benefits and alternatives. Importance of Comprehensive Evaluation Risk stratification: Identify potential complications. Perioperative planning: Optimize patient condition. Anesthetic strategy: Tailor to patient needs.

Answer 92

Correct Answer A) Complete heart block Explanation Complete heart block (CHB) is characterized by: Atrioventricular (AV) block: 2:1 or 3:1 block. Exertional dyspnea: Reduced cardiac output. Fatigue: Decreased exercise tolerance. Palpitations: Awareness of abnormal heart rhythm. Diagnostic Features Electrocardiogram (ECG): AV block, widened QRS. Echocardiogram: Confirm AV block, rule out structural anomalies. Holter monitor: Document arrhythmias. Management Pacemaker implantation: Corrects AV block. Medical therapy: Symptomatic relief. Differential Diagnosis Wolff-Parkinson-White (WPW) syndrome (B): Pre-excitation, tachycardia. Atrioventricular canal defect (C): Congenital heart defect, heart failure. Ebstein's anomaly (D): Congenital tricuspid valve anomaly. Key Considerations Early diagnosis: Prevents complications. Pacemaker timing: Based on symptoms, age and block severity. Long-term follow-up: Monitor pacemaker function.

Answer 93

Answer and Explanation Correct answer: A) Glioblastoma multiforme Explanation Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor. Clinical Features Progressive hemiparesis: Weakness on one side. Seizures: Focal or generalized. Cognitive decline: Memory, language or personality changes. Headache and nausea: Increased intracranial pressure. Diagnostic Imaging MRI: Heterogeneous, contrast-enhancing mass. CT scan: Hyperdense or isodense lesion. Histopathology High-grade astrocytoma: Microscopic examination. Necrosis and angiogenesis: Hallmark features. Management Surgical resection: Maximal safe removal. Radiation therapy: Adjuvant treatment. Chemotherapy: Temozolomide. Supportive care: Seizure control, symptom management. Differential Diagnosis Meningioma (B): Extra-axial, well-circumscribed. Brain metastasis (C): Multiple lesions, known primary cancer. Low-grade glioma (D): Slower progression, better prognosis. Key Considerations Multidisciplinary team: Neurosurgeon, oncologist, radiologist collaboration. Surgical planning: Functional MRI, neuronavigation. Prognosis: Generally poor, 5-year survival <10%.

Answer 94

Correct answer: A) Malaria Explanation Malaria is a mosquito-borne disease prevalent in Africa, characterized by: Clinical Features Fever: Recurring, cyclical. Chills: Rigors, sweating. Flu-like symptoms: Headache, fatigue, muscle aches. Thrombocytopenia: Low platelet count. Elevated liver enzymes: Hepatocellular damage. Diagnostic Tests Peripheral smear: Parasites in red blood cells. Rapid diagnostic tests (RDTs): Antigen detection. PCR: Molecular confirmation. Management Artemisinin-based combination therapy (ACT): First-line treatment. Supportive care: Fluids, antipyretics. Hospitalization: Severe cases, monitoring. Differential Diagnosis Typhoid fever (B): Salmonella Typhi infection, abdominal symptoms. Yellow fever (C): Hemorrhagic fever, jaundice. Dengue fever (D): Severe flu-like illness, hemorrhagic manifestations. Key Considerations Prompt diagnosis: Prevents complications. Chemoprophylaxis: For travelers to endemic areas. Vector control: Mosquito elimination.

Answer 95

Correct Answer: D. Heparin is the most appropriate initial pharmacotherapy for managing acute renal vein thrombosis in this patient. Renal vein thrombosis is a known complication of nephrotic syndrome, particularly with membranous nephropathy, due to the hypercoagulable state induced by loss of antithrombin III, increased fibrinogen levels, and other prothrombotic factors. The patient's presentation with sudden flank pain, hematuria, and ultrasound findings supports this diagnosis. Immediate anticoagulation with heparin is crucial to prevent further thrombus propagation and potential complications such as renal infarction or pulmonary embolism. Heparin acts quickly to inhibit clot formation by activating antithrombin III, which then inactivates thrombin and factor Xa. Following stabilization with heparin, long-term anticoagulation with warfarin may be considered. Incorrect Answer Explanation: Aspirin (Answer A) is an antiplatelet agent that inhibits cyclooxygenase, reducing thromboxane A2 production and platelet aggregation. While aspirin is useful in preventing arterial thrombosis, it is not effective for treating venous thrombosis, such as renal vein thrombosis, where anticoagulation is required. Aspirin would not address the underlying hypercoagulable state associated with nephrotic syndrome. It is more commonly used for cardiovascular disease prevention and management of conditions like myocardial infarction and stroke. Warfarin (Answer B) is an oral anticoagulant that inhibits vitamin K-dependent clotting factors (II, VII, IX, X). While it is used for long-term anticoagulation following initial treatment with heparin, it is not suitable for immediate management of acute thrombosis due to its delayed onset of action. Warfarin requires several days to achieve therapeutic anticoagulation, making it inappropriate for the acute setting where rapid anticoagulation is necessary. Initiating treatment with heparin allows for immediate anticoagulation, after which transition to warfarin can be considered for long-term management. Tissue plasminogen activator (tPA) (Answer C) is a thrombolytic agent used to dissolve existing clots by converting plasminogen to plasmin, which degrades fibrin. While tPA is used in certain acute situations, such as ischemic stroke or massive pulmonary embolism, it carries a significant risk of bleeding and is not typically used for renal vein thrombosis. The risks associated with thrombolysis, including hemorrhagic complications, generally outweigh the benefits in this context, especially when anticoagulation with heparin is effective and safer for managing venous thrombosis. Clopidogrel (Answer E) is another antiplatelet agent that inhibits the P2Y12 component of ADP receptors on platelets, preventing platelet aggregation. Similar to aspirin, clopidogrel is used for arterial thrombosis prevention and is not effective for treating venous thrombosis like renal vein thrombosis. Anticoagulation, rather than antiplatelet therapy, is required to manage the hypercoagulable state and thrombus in this patient. Clopidogrel is often used in conjunction with aspirin for dual antiplatelet therapy in conditions like acute coronary syndromes and after stent placement.

Answer 96

Thank you for your answer. The correct answer is C. Serratus anterior. Explanation: The long thoracic nerve (C5, C6, C7) specifically innervates the serratus anterior muscle. This nerve runs along the lateral chest wall and can be injured during procedures like radical mastectomy. When damaged, it results in “winging of the scapula” because the serratus anterior is responsible for holding the scapula against the thoracic wall and rotating it during arm elevation. The other muscles listed are innervated by different nerves: • Anterior and Middle scalene: Branches from cervical spinal nerves • Subscapularis: Subscapular nerve (from posterior cord of brachial plexus) • Teres major: Lower subscapular nerve (from posterior cord of brachial plexus)

Answer 97

Thank you for your answer. The correct answer is E. Triceps brachii. Explanation: The triceps brachii muscle inserts on the olecranon process of the ulna. When there is a fracture of the olecranon process, the insertion of the triceps brachii is disrupted. The triceps is the primary extensor of the elbow joint and consists of three heads (long, lateral, and medial). The other muscles listed have different insertions: • Brachialis: Inserts on the coronoid process and tuberosity of the ulna • Flexor digitorum profundus: Inserts on the distal phalanges of fingers 2-5 • Flexor pollicis longus: Inserts on the distal phalanx of the thumb • Pronator teres: Inserts on the middle third of the lateral surface of the radius

Answer 98

Thank you for your answer. The correct answer is D. Thoracodorsal nerve. Explanation: The thoracodorsal nerve innervates the latissimus dorsi muscle, which is a powerful extensor of the shoulder joint (specifically, it extends, adducts, and medially rotates the humerus). When this nerve is injured, extension of the humerus becomes limited. The other nerves listed have different functions: • Long thoracic nerve: Innervates the serratus anterior muscle • Medial pectoral nerve: Innervates the pectoralis major and minor muscles • Suprascapular nerve: Innervates the supraspinatus and infraspinatus muscles • Upper subscapular nerve: Innervates the subscapularis muscle

Answer 99

Thank you for your answer. The correct answer is A. Encircles the head of the radius. Explanation: The annular ligament is a strong band of fibers that encircles the head of the radius and holds it in place against the radial notch of the ulna at the proximal radioulnar joint. It allows the radius to rotate during pronation and supination movements of the forearm while maintaining joint stability. When sprained, it can cause pain and limited rotation of the forearm. This injury is common in children and is sometimes called “nursemaid’s elbow” or “pulled elbow” when the radial head partially dislocates from the annular ligament.

Answer 100

Thank you for your answer. The correct answer is B. Elbow joint. Explanation: The brachial artery gives off several branches that contribute to the anastomotic circulation around the elbow joint. These include: • The superior ulnar collateral artery • The inferior ulnar collateral artery • The radial recurrent artery • The anterior and posterior ulnar recurrent arteries These branches form an anastomotic network around the elbow joint that provides collateral circulation when the main vessels are obstructed. This is clinically important during injuries or surgical procedures involving the elbow region. The other joints listed have different arterial supplies: • Acromioclavicular joint: Branches from the suprascapular and thoracoacromial arteries • Glenohumeral joint: Branches from the anterior and posterior circumflex humeral arteries • Head of the humerus: Primarily supplied by the anterior and posterior circumflex humeral arteries • Scapula: Supplied by the suprascapular, subscapular, and dorsal scapular arteries

Answer 101

Thank you for your answer. The correct answer is D. Initiation of abduction of the humerus. Explanation: The supraspinatus muscle is one of the four rotator cuff muscles. Its primary function is to initiate abduction of the arm (the first 15-30 degrees). After this initial movement, the deltoid muscle takes over to continue abduction beyond 30 degrees. The supraspinatus also helps stabilize the glenohumeral joint by keeping the head of the humerus in the glenoid fossa. The other options are incorrect because: • Adduction of the humerus: Primarily performed by pectoralis major, latissimus dorsi, and teres major • Abduction above the horizontal plane: Primarily performed by the deltoid muscle • Lateral rotation of the humerus: Primarily performed by infraspinatus and teres minor • Superior rotation of the scapula: Primarily performed by the trapezius and serratus anterior

Answer 102

Thank you for your answer. The correct answer is C. Accompanies the long thoracic nerve to the serratus anterior muscle. Explanation: The lateral thoracic artery is a branch of the axillary artery (second part) and runs along the lateral border of the pectoralis minor muscle. It supplies the serratus anterior muscle and accompanies the long thoracic nerve. It also supplies the lateral aspect of the breast and forms anastomoses with the intercostal arteries. The other options are incorrect because: • The lateral thoracic artery is not a branch of the subclavian or brachial artery • It does not accompany the thoracodorsal nerve (which supplies the latissimus dorsi muscle) • It does not emerge through the triangular space (the circumflex scapular artery passes through the triangular space)

Answer 103

Thank you for your answer. The correct answer is A. Pectoralis minor. Explanation: The pectoralis minor muscle originates from the 3rd to 5th ribs and inserts on the coracoid process of the scapula. When it contracts, it directly pulls the scapula (and thus the glenoid fossa) downward and forward, causing depression of the glenoid fossa. It also assists in downward rotation of the scapula. The other muscles have different actions: • Serratus anterior: Primarily protracts the scapula and rotates it upward • Pectoralis major: Acts on the humerus (not the scapula), adducting and medially rotating it • Latissimus dorsi: Acts on the humerus, extending, adducting, and medially rotating it • Supraspinatus: Acts on the humerus, initiating abduction

Answer 104

Thank you for your answer. The correct answer is A. Flexor digitorum superficialis. Explanation: The common flexor tendon (also known as the common flexor origin) attaches to the medial epicondyle of the humerus. The muscles that originate from this common tendon include: • Flexor digitorum superficialis (partially) • Flexor carpi radialis • Palmaris longus • Flexor carpi ulnaris • Pronator teres The other muscles mentioned have different origins: • Flexor digitorum profundus: Originates from the anterior and medial surfaces of the ulna • Flexor pollicis longus: Originates from the anterior surface of the radius • Pronator quadratus: Originates from the distal fourth of the anterior surface of the ulna • Extensor carpi ulnaris: Originates from the common extensor tendon on the lateral epicondyle of the humerus

Answer 105

Thank you for your answer. The correct answer is C. Extensor carpi radialis brevis and flexor carpi radialis. Explanation: Abduction of the wrist (radial deviation) is produced by the combined action of extensor carpi radialis brevis and flexor carpi radialis. These muscles are positioned on the radial (thumb) side of the forearm and wrist. When they contract together, they pull the wrist toward the radial side, causing radial deviation (abduction). The other combinations have different actions: • Pronator teres and brachioradialis: Primarily involved in pronation and elbow flexion, respectively • Palmaris longus and extensor digitorum: Involved in wrist flexion and finger extension, respectively • Extensor carpi radialis brevis and extensor carpi ulnaris: When acting together, they extend the wrist but do not cause radial deviation • Supinator and extensor pollicis longus: Involved in supination and thumb extension, respectively

Answer 106

Thank you for your answer. The correct answer is D. All of the adductors of the digits take at least part of their attachments from metacarpal bones. Explanation: The adductors of the digits include the palmar interosseous muscles and the adductor pollicis muscle. All of these muscles have at least part of their attachments from the metacarpal bones: • The palmar interosseous muscles (which adduct the 2nd, 4th, and 5th digits toward the middle finger) originate from the metacarpal bones of the fingers they act upon. • The adductor pollicis muscle (which adducts the thumb) has two heads: the transverse head originates from the third metacarpal bone, and the oblique head originates from the capitate bone, the bases of the 2nd and 3rd metacarpals, and the adjacent carpal bones. The other options are incorrect: • The palmar interosseous muscles are not the sole adductors (the adductor pollicis also performs adduction) • The lumbrical muscles flex the metacarpophalangeal joints and extend the interphalangeal joints; they don’t adduct digits • There is only one adductor muscle of the thumb (adductor pollicis), though it has two heads • Carpal tunnel syndrome affects the median nerve, which doesn’t innervate the adductors of the digits (palmar interossei are innervated by the ulnar nerve)

Answer 107

Thank you for your answer. The correct answer is A. Ulnar nerve. Explanation: The ulnar nerve innervates all the intrinsic muscles responsible for digit adduction in the hand. These include: • All palmar interosseous muscles (which adduct the index, ring, and little fingers toward the middle finger) • The adductor pollicis muscle (which adducts the thumb) The ulnar nerve supplies most of the intrinsic muscles of the hand, including all the hypothenar muscles, the deep branch of the ulnar nerve supplies all the interossei (both palmar and dorsal), the 3rd and 4th lumbricals, adductor pollicis, and the deep head of flexor pollicis brevis. The other nerves have different functions: • Median nerve: Supplies the thenar muscles and the 1st and 2nd lumbricals • Radial nerve: Supplies the extensor muscles of the forearm and hand • Upper subscapular nerve: Supplies the subscapularis muscle • Musculocutaneous nerve: Supplies the flexor muscles of the arm

Answer 108

Thank you for your answer. The correct answer is D. Lateral pectoral. Explanation: The lateral cord of the brachial plexus gives rise to the following nerves: • Lateral pectoral nerve (supplies the pectoralis major muscle) • Musculocutaneous nerve • Lateral root of the median nerve The other nerves originate from different parts of the brachial plexus: • Ulnar nerve: Comes from the medial cord • Medial pectoral nerve: Comes from the medial cord • Suprascapular nerve: Comes from the upper trunk (C5, C6) • Thoracodorsal nerve: Comes from the posterior cord The lateral pectoral nerve supplies the pectoralis major muscle, and injury to this nerve during axillary surgery can result in weakness of the pectoralis major, affecting arm adduction and medial rotation.

Answer 109

Thank you for your answer. The correct answer is C. The hypothenar muscles would be completely paralysed. Explanation: A spinal cord injury at the C8 level would affect the C8 nerve root and all nerve roots below it. The C8 nerve root contributes significantly to the ulnar nerve, which innervates the hypothenar muscles (abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi). Therefore, with a C8 spinal cord injury, the hypothenar muscles would be completely paralyzed. The other options are incorrect because: • The brachialis muscle is primarily innervated by C5-C6 (via the musculocutaneous nerve), which would be spared in a C8 injury • The radial nerve receives contributions from C5-T1, and its proximal muscles (triceps) are mainly supplied by C7-C8, but not exclusively C8 • The deltoid muscle is innervated by C5-C6 (via the axillary nerve), which would be spared in a C8 injury • Flexion of the humerus is primarily controlled by muscles innervated by C5-C6 (biceps, brachialis), which would be spared in a C8 injury

Answer 110

Thank you for your answer. The correct answer is E. Tendon of the long head of the biceps brachii muscle. Explanation: The intertubercular groove (also called the bicipital groove) is a vertical groove located between the greater and lesser tubercles on the proximal humerus. It contains the tendon of the long head of the biceps brachii muscle, which originates from the supraglenoid tubercle of the scapula. The tendon passes through the shoulder joint, then travels down the intertubercular groove, where it is held in place by the transverse humeral ligament. The other options are incorrect because: • The pectoralis minor inserts on the coracoid process of the scapula • The long head of the triceps brachii originates from the infraglenoid tubercle of the scapula • The coracobrachialis originates from the coracoid process and inserts on the medial surface of the humerus • The short head of the biceps brachii originates from the coracoid process of the scapula

Answer 111

Thank you for your answer. The correct answer is C. Brachial. Explanation: The superior ulnar collateral artery is a direct branch of the brachial artery. It typically arises from the brachial artery in the middle of the arm and runs with the ulnar nerve behind the medial intermuscular septum. It contributes to the anastomotic network around the elbow joint, specifically the periarticular arterial anastomosis. This network is important as it provides collateral circulation when the main vessels are obstructed. The other options are incorrect because: • The ulnar artery gives rise to anterior and posterior ulnar recurrent arteries, not the superior ulnar collateral • The radial artery gives rise to the radial recurrent artery • The profunda brachii (deep brachial artery) is itself a branch of the brachial artery • The axillary artery becomes the brachial artery at the lower border of the teres major muscle

Answer 112

Thank you for your answer. The correct answer is D. Form the trunks of the brachial plexus. Explanation: The primary ventral rami of the brachial plexus (C5-T1) form the trunks of the brachial plexus. Specifically: • The ventral rami of C5 and C6 unite to form the upper trunk • The ventral ramus of C7 continues as the middle trunk • The ventral rami of C8 and T1 unite to form the lower trunk These trunks then divide into anterior and posterior divisions, which regroup to form the cords of the brachial plexus. The other options are incorrect because: • The ventral rami emerge between the anterior and middle scalene muscles (not middle and posterior) • The brachial plexus is typically formed from spinal levels C5 to T1 (not C7 to T3) • The ventral rami do give rise to some nerves directly (e.g., dorsal scapular nerve from C5, long thoracic nerve from C5-C7) • The trunks form the divisions, which then form the cords (the ventral rami don’t directly form the cords)

Answer 113

Thank you for your answer. The correct answer is B. Pronator teres. Explanation: The main movements at the proximal radioulnar joint are pronation and supination of the forearm. The pronator teres is the primary muscle responsible for pronation at this joint. It has two heads: the humeral head (from the medial epicondyle of the humerus) and the ulnar head (from the coronoid process of the ulna). It inserts on the lateral surface of the radius. A stab wound to the cubital fossa could damage the median nerve, which innervates the pronator teres, resulting in weakness of pronation. The other options are incorrect because: • Extensor carpi ulnaris: Primarily extends and adducts the wrist • Triceps brachii: Extends the elbow joint • Brachioradialis: Primarily flexes the elbow joint (can assist with both pronation and supination) • Brachialis: Flexes the elbow joint

Answer 114

Thank you for your answer. The correct answer is E. It prevents the tendons of the posterior compartment of the forearm from ‘bowstringing’ when the hand is extended at the wrist. Explanation: The extensor retinaculum is a strong fibrous band that runs obliquely across the back of the wrist. Its primary function is to hold the extensor tendons in place and prevent them from “bowstringing” (lifting away from the bone) when the wrist is extended. It creates six compartments through which the extensor tendons pass. The other options are incorrect because: • The extensor retinaculum is not a direct extension of the axillary fascia • The median nerve passes through the carpal tunnel deep to the flexor retinaculum (not the extensor retinaculum) • The brachioradialis tendon inserts on the radius proximal to the wrist and does not pass through the extensor retinaculum • The extensor retinaculum does not contain a compartment for the thenar muscles (these are intrinsic hand muscles)

Answer 115

Thank you for your answer. The correct answer is D. Anterior aspect of the elbow. Explanation: The median cubital vein is located in the anterior aspect of the elbow (the cubital fossa). It is a superficial vein that connects the cephalic vein (laterally) with the basilic vein (medially) and crosses the cubital fossa. This vein is commonly used for venipuncture (blood drawing) and intravenous access because it is usually visible, relatively large, and easily accessible in the anterior aspect of the elbow. The other options are incorrect because: • The posterior aspect of the knee does not contain the median cubital vein • The femoral triangle contains the femoral vein, not the median cubital vein • The dorsal surface of the hand contains dorsal venous networks, not the median cubital vein • The deltopectoral triangle contains the cephalic vein, not the median cubital vein

Answer 116

Thank you for your answer. The correct answer is C. Olecranon process of the ulna. Explanation: When you rest your elbows on a desk, you are resting on the olecranon process of the ulna. The olecranon process is the large, curved bony prominence at the proximal end of the ulna that forms the point of the elbow. It serves as the attachment site for the triceps brachii muscle and is easily palpable beneath the skin. This is the part that makes contact with surfaces when you “lean on your elbows.” The other options are incorrect because: • The styloid process of the radius is located at the distal end of the radius at the wrist • The deltoid tuberosity is located on the lateral surface of the humerus (upper arm) • The coronoid process of the ulna is located on the anterior aspect of the proximal ulna and is not superficial • The radial tuberosity is located on the medial side of the proximal radius and is not superficial

Answer 117

Thank you for your answer. The correct answer is D. Teres minor. Explanation: The rotator cuff is a group of four muscles and their tendons that surround the shoulder joint and provide stability and movement. The four muscles that make up the rotator cuff are: 1. Supraspinatus 2. Infraspinatus 3. Subscapularis 4. Teres minor The teres minor originates from the lateral border of the scapula and inserts on the greater tubercle of the humerus. It functions to laterally rotate the arm and stabilize the shoulder joint. The other options are incorrect because: • Deltoid: This is a large, triangular muscle that covers the shoulder joint but is not part of the rotator cuff • Subclavius: This small muscle runs from the first rib to the clavicle • Long head of the biceps brachii: Although its tendon passes through the shoulder joint, it is not considered part of the rotator cuff • Coracobrachialis: This muscle runs from the coracoid process to the humerus and is not part of the rotator cuff

Answer 118

Thank you for your answer. The correct answer is C. Scaphoid. Explanation: The distal end of the radius articulates primarily with the scaphoid and lunate bones of the proximal row of carpal bones when the wrist is in the anatomical position. The scaphoid is the most commonly fractured carpal bone, especially during falls on an outstretched hand (FOOSH injuries). This is because the scaphoid acts as a link between the proximal and distal rows of carpal bones and bears much of the force transmitted through the wrist during such falls. The other options are incorrect because: • Triquetrum: Articulates primarily with the lunate and hamate • Capitate: Articulates primarily with the lunate, scaphoid, trapezoid, and hamate • Pisiform: Articulates with the triquetrum and does not articulate with the radius • Trapezium: Articulates with the scaphoid and first metacarpal

Answer 119

Thank you for your answer. The correct answer is B. Hinge. Explanation: The elbow joint is classified as a hinge joint (ginglymus). It allows movement primarily in one plane (flexion and extension) around a single axis, similar to a door hinge. The elbow joint is formed by the articulation between the trochlea of the humerus and the trochlear notch of the ulna, and between the capitulum of the humerus and the head of the radius. The other options are incorrect because: • Ellipsoid: Allows movement in two planes (e.g., wrist joint between radius and carpal bones) • Ball and socket: Allows movement in multiple planes (e.g., hip and shoulder joints) • Plane: Allows gliding movements (e.g., intercarpal joints) • Bicondylar: Has two distinct articular surfaces (e.g., knee joint)

Answer 120

Thank you for your answer. The correct answer is D. Lower subscapular. Explanation: The muscle that inserts onto the crest of the lesser tubercle of the humerus is the teres major muscle. The teres major is innervated by the lower subscapular nerve, which is a branch of the posterior cord of the brachial plexus. The teres major muscle acts to adduct, medially rotate, and extend the arm at the shoulder joint. The other options are incorrect because: • Radial nerve: Innervates the triceps brachii and muscles of the posterior compartment of the forearm • Long thoracic nerve: Innervates the serratus anterior muscle • Median nerve: Innervates most of the anterior forearm muscles and some intrinsic hand muscles • Axillary nerve: Innervates the deltoid and teres minor muscles

Answer 121

Thank you for your answer. The correct answer is B. Flexion in the distal interphalangeal joint of digit 5. Explanation: The nerve that runs posterior to the medial epicondyle of the humerus is the ulnar nerve. When damaged at this location (a common injury known as “cubital tunnel syndrome”), it typically affects: • Flexion of the distal interphalangeal joints of the 4th and 5th digits (via the flexor digitorum profundus muscle for these digits) • The intrinsic hand muscles innervated by the ulnar nerve (hypothenar muscles, interossei, adductor pollicis, and the 3rd and 4th lumbricals) The other options are incorrect because: • Extension of the metacarpophalangeal joints is primarily controlled by the extensor digitorum, which is innervated by the radial nerve • Abduction of the thumb is primarily controlled by the abductor pollicis brevis, which is innervated by the median nerve • Cutaneous sensation over the thenar eminence is supplied by the median nerve • The 1st and 2nd lumbricals are innervated by the median nerve, not the ulnar nerve

Answer 122

Thank you for your answer. The correct answer is A. Latissimus dorsi. Explanation: The posterior wall of the axilla is formed by the subscapularis muscle, teres major muscle, and latissimus dorsi muscle, all overlying the scapula. The latissimus dorsi is a large, flat muscle that covers the lower part of the back and forms part of the posterior axillary fold. It originates from the spinous processes of the lower thoracic vertebrae, thoracolumbar fascia, iliac crest, and the lower ribs, and inserts onto the intertubercular groove of the humerus. It functions to extend, adduct, and medially rotate the arm. The other options are incorrect because: • Trapezius: Located in the upper back and neck, not part of the axillary walls • Pectoralis major: Forms the anterior wall of the axilla • Serratus anterior: Forms the medial wall of the axilla • Supraspinatus: Located in the supraspinous fossa of the scapula, not part of the axillary walls

Answer 123

Thank you for your answer. The correct answer is C. C5, C6, C7, C8 and T1. Explanation: The posterior cord of the brachial plexus contains nerve fibers from all the roots that contribute to the brachial plexus (C5, C6, C7, C8, and T1). The posterior cord is formed by the posterior divisions of the upper, middle, and lower trunks of the brachial plexus. Since all three trunks contribute to the posterior cord, it contains fibers from all five spinal nerve roots (C5-T1). The posterior cord gives rise to several important nerves: • Axillary nerve (C5, C6) • Radial nerve (C5, C6, C7, C8, T1) • Upper and lower subscapular nerves (C5, C6) • Thoracodorsal nerve (C6, C7, C8) The other options are incorrect because they do not include the full range of spinal levels that contribute to the posterior cord.

Answer 124

Thank you for your answer. The correct answer is A. Subclavian → axillary → subscapular → thoracodorsal. Explanation: The blood supply to the latissimus dorsi muscle follows this pathway: 1. The subclavian artery continues as the axillary artery as it passes the lateral border of the first rib 2. The axillary artery gives off the subscapular artery (its largest branch) at the lower border of the subscapularis muscle 3. The subscapular artery gives off the thoracodorsal artery, which runs along with the thoracodorsal nerve to supply the latissimus dorsi muscle The other options are incorrect because: • There is no “acromioclavicular artery” (option B) • The supreme thoracic artery supplies the first and second intercostal spaces, not the latissimus dorsi (option C) • The thoracervical trunk gives rise to the suprascapular artery, which supplies the supraspinatus and infraspinatus muscles, not the latissimus dorsi (option D) • The costocervical trunk supplies deep muscles of the neck, not the latissimus dorsi (option E)

Answer 125

Thank you for your answer. The correct answer is B. It contains nerve fibres from C5 and C6 spinal cord segments. Explanation: The suprascapular nerve is derived from the upper trunk of the brachial plexus (not the middle trunk) and contains fibers from the C5 and C6 spinal cord segments. It passes through the suprascapular notch under (not superior to) the suprascapular ligament to reach the supraspinatus muscle. It innervates both the supraspinatus and infraspinatus muscles (not the teres minor, which is innervated by the axillary nerve). The suprascapular nerve is primarily a motor nerve and provides minimal cutaneous innervation; it does not provide cutaneous innervation to the posterolateral surface of the shoulder (this area is supplied by the axillary nerve and supraclavicular nerves).

Answer 126

Thank you for your answer. The correct answer is B. Radial. Explanation: The symptoms described (pins and needles on the dorsum of the hand, over the thumb and first two digits, along with weakness of wrist dorsiflexion and finger extension) are classic signs of radial nerve injury. The radial nerve provides: 1. Motor innervation to the extensor muscles of the forearm, which are responsible for wrist dorsiflexion (extension) and finger extension 2. Sensory innervation to the posterior (dorsal) aspect of the arm, forearm, and the dorsolateral surface of the hand, including the dorsum of the thumb, index finger, middle finger, and the radial half of the ring finger The other options are incorrect because: • Ulnar nerve: Affects the medial side of the hand, including the little finger and half of the ring finger • Musculocutaneous nerve: Primarily affects the lateral forearm • Axillary nerve: Affects the lateral aspect of the shoulder • Median nerve: Affects the palmar aspect of the lateral 3.5 digits, not the dorsum

Answer 127

Thank you for your answer. The correct answer is A. Superior ulnar collateral. Explanation: The superior ulnar collateral artery is a branch of the brachial artery that accompanies the ulnar nerve as it passes posterior to the medial epicondyle of the humerus through the cubital tunnel. This artery runs with the ulnar nerve behind the medial intermuscular septum and contributes to the anastomotic network around the elbow joint. In a fracture of the medial epicondyle, this artery is at risk of laceration due to its close proximity to the bone. The other options are incorrect because: • Anterior ulnar recurrent artery: Arises from the ulnar artery and passes anterior to the medial epicondyle • Radial collateral artery: Branch of the profunda brachii artery that runs with the radial nerve • Middle collateral artery: Branch of the profunda brachii artery that supplies the lateral aspect of the elbow • Interosseous recurrent artery: Branch of the posterior interosseous artery that does not course near the medial epicondyle

Answer 128

Thank you for your answer. The correct answer is C. Posterior circumflex humeral artery. Explanation: The quadrangular space (also called the lateral axillary space) is bounded by: • Teres minor muscle (superiorly) • Teres major muscle (inferiorly) • Long head of triceps brachii muscle (medially) • Surgical neck of the humerus (laterally) This space contains the axillary nerve and the posterior circumflex humeral artery. The axillary nerve supplies the deltoid and teres minor muscles, while the posterior circumflex humeral artery is a branch of the third part of the axillary artery that accompanies the axillary nerve to supply the shoulder joint and surrounding muscles. The other options are incorrect because: • Circumflex scapular artery: Passes through the triangular space, not the quadrangular space • Radial nerve: Passes through the triangular interval, not the quadrangular space • Deep artery of the arm (profunda brachii): Accompanies the radial nerve in the spiral groove • Thoracodorsal nerve: Runs with the thoracodorsal artery to the latissimus dorsi

Answer 129

Thank you for your answer. The correct answer is B. Musculocutaneous. Explanation: The musculocutaneous nerve innervates all the muscles of the anterior compartment of the arm, which include: • Biceps brachii • Brachialis • Coracobrachialis These muscles are primarily responsible for flexion of the elbow joint. The musculocutaneous nerve arises from the lateral cord of the brachial plexus (C5-C7) and also provides sensory innervation to the lateral forearm via its terminal branch, the lateral antebrachial cutaneous nerve. The other options are incorrect because: • Median nerve: Primarily innervates muscles in the anterior compartment of the forearm, not the arm • Radial nerve: Innervates muscles in the posterior compartment of the arm and forearm • Ulnar nerve: Primarily innervates muscles in the anterior compartment of the forearm and intrinsic hand muscles • Axillary nerve: Innervates the deltoid and teres minor muscles

Answer 130

Thank you for your answer. The correct answer is B. Rhomboid major. Explanation: The serratus anterior muscle is the primary protractor of the scapula (it pulls the scapula forward and around the thoracic wall). The antagonist muscles that oppose this action are the rhomboid major and rhomboid minor, which retract the scapula (pull it toward the spine). The rhomboid major is the larger of these muscles and originates from the spinous processes of T2-T5 vertebrae and inserts on the medial border of the scapula. The other options are incorrect because: • Levator scapula: Primarily elevates the scapula rather than retracting it • Pectoralis minor: Acts as a synergist with serratus anterior in protraction, not an antagonist • Supraspinatus: Acts on the glenohumeral joint to abduct the arm, not on scapular movement • Deltoid: Acts on the glenohumeral joint to abduct the arm, not on scapular movement

Answer 131

The correct answer is A: Anterior communicating artery Explanation: This patient has a classical presentation of a ruptured berry aneurysm resulting in subarachnoid hemorrhage. The anterior communicating artery is the most common site for berry aneurysms. The sudden onset severe headache described as a “hammer blow” is typical of subarachnoid hemorrhage. The anterior communicating artery is located in the anterior cranial fossa, which matches the MRI findings.

Answer 132

The correct answer is A: Cribriform plate of the ethmoid bone Explanation: The cribriform plate of the ethmoid bone is a common site of fracture in anterior cranial fossa injuries. The olfactory nerve filaments pass through the cribriform plate, and damage to these structures results in anosmia (loss of smell). Cerebrospinal fluid rhinorrhea occurs when there is a tear in the dura, allowing CSF to leak through the fracture into the nasal cavity.

Answer 133

The correct answer is E: Uncus of the temporal lobe Explanation: The uncus of the temporal lobe herniates through the tentorial hiatus in cases of raised intracranial pressure, compressing the oculomotor nerve (3rd cranial nerve) against the edge of the tentorium. This results in a dilated pupil on the same side as the lesion. This is known as uncal herniation and is a neurosurgical emergency that can occur with extradural hemorrhage due to increased intracranial pressure.

Answer 134

The correct answer is B: Hypoglossal nerve Explanation: When the hypoglossal nerve (12th cranial nerve) is affected, the tongue deviates toward the side of the lesion when protruded. This is because the hypoglossal nerve supplies the intrinsic and extrinsic muscles of the tongue except for the palatoglossus. In this case, the nasopharyngeal carcinoma has extended into the right posterior base of the skull, affecting the right hypoglossal nerve as it exits the skull through the hypoglossal canal. This results in weakness of the right side of the tongue, causing it to deviate toward the right (the side of the lesion) when protruded.

Answer 135

The correct answer is C: Middle meningeal artery Explanation: The middle meningeal artery is a branch of the maxillary artery which along with the superficial temporal artery is one of the terminal branches of the external carotid artery. It enters the middle cranial fossa through the foramen spinosum and divides into an anterior and posterior branch. It is the cause of bleeding in extradural haemorrhage because it lies deep to the squamous part of the temporal bone which is a very thin part of the cranium, and therefore easily fractured. This type of injury is common in contact sports like football, where a blow to the head can fracture the temporal bone and tear the middle meningeal artery.

Answer 136

The correct answer is D: Intracranial tumour Explanation: This woman has clinical features of raised intracranial pressure with focal neurological deficits suggestive of a tumour in the vicinity of the 8th cranial (vestibulocochlear) nerve. She has tinnitus, deafness and vertigo, symptoms that confirm the suspicion. Facial numbness and weakness point to compression of the 5th (trigeminal) and 7th (facial) cranial nerves. The diagnosis is an acoustic neuroma that arises at the cerebellopontine angle.

Answer 137

The correct answer is E: Pyloric stenosis Explanation: Pyloric stenosis typically presents with projectile vomiting in infants around 2-8 weeks of age. The vomiting is non-bilious and occurs immediately after feeds. The condition is more common in males and firstborn children. On examination, a palpable olive-shaped mass may be felt in the right upper quadrant, representing the hypertrophied pylorus.

Answer 138

The correct answer is: B. Chest X-ray Explanation: A positive Heaf test (or tuberculin skin test) indicates prior exposure to Mycobacterium tuberculosis, either through infection or BCG vaccination. However, Heaf tests are no longer commonly used, having been replaced by the Mantoux test in many places, but both serve to assess TB exposure. In this case, since the individual is about to travel to a TB-endemic area (Uganda) and has a positive skin test, the next appropriate step is to exclude active TB disease before considering prophylactic treatment or concluding no action is needed. A chest X-ray helps to: • Identify any signs of active pulmonary TB. • Determine if the positive test is due to latent TB infection (LTBI) without active disease. Other options: • A. BCG vaccination: Not indicated because a positive skin test suggests previous exposure or immunization. • C. Isoniazid prophylaxis: Only appropriate after excluding active TB. • D. Mantoux test: Redundant since a positive Heaf test already indicates exposure. • E. No action: Not appropriate without ruling out active disease.

Answer 139

Thank you for your answer. The correct answer is E. Long thoracic nerve. Explanation: “Winged scapula” is a clinical sign where the medial border of the scapula protrudes from the back like a wing. This occurs due to weakness or paralysis of the serratus anterior muscle, which is innervated by the long thoracic nerve (C5-C7). The serratus anterior muscle holds the scapula against the thoracic wall and is essential for proper scapular movement during arm elevation. During a radical mastectomy with axillary lymph node dissection, the long thoracic nerve is at risk of injury as it runs along the lateral chest wall through the axilla. When damaged, the serratus anterior muscle cannot function properly, resulting in the characteristic winging of the scapula, especially when the patient pushes against resistance. The other options are incorrect because: • Axillary nerve: Innervates the deltoid and teres minor muscles • Musculocutaneous nerve: Innervates the anterior compartment of the arm • Lower subscapular nerve: Innervates the teres major muscle • Medial pectoral nerve: Innervates the pectoralis major and minor muscles

Answer 140

The correct answer is C: Larynx is higher and more anterior in the neck than the adult Explanation: In children, the larynx is positioned higher and more anteriorly in the neck compared to adults. This anatomical difference can make airway management more challenging during anesthesia and increases the risk of respiratory difficulties. This positioning difference affects the ease of intubation and can lead to complications during inhalational anesthesia administration.

Answer 141

The correct answer is E: Torsion of the testis Explanation: Testicular torsion typically presents with acute scrotal pain that may radiate to the lower abdomen. The pain can sometimes be more prominent in the abdomen, leading to confusion with appendicitis. The soft, non-tender abdomen makes appendicitis less likely. Testicular torsion is a surgical emergency requiring immediate intervention to save the testicle.

Answer 142

The correct answer is A: Core biopsy Explanation: When fine needle aspiration cytology (FNAC) shows malignant cells, the next step is to perform a core biopsy. This provides tissue for histological examination, hormone receptor status, and HER2 status, which are essential for planning definitive treatment. Core biopsy provides more information than FNAC and helps determine the most appropriate surgical approach and whether neoadjuvant therapy is indicated.

Answer 143

The correct answer is C: Esophageal carcinoma Explanation: Progressive dysphagia for solids in an older patient with a filling defect on barium swallow is highly suggestive of esophageal carcinoma. Esophageal cancer typically presents with progressive dysphagia, initially for solids and later for liquids, often accompanied by weight loss. The lower third of the esophagus is a common site for adenocarcinoma, which is associated with Barrett’s esophagus and chronic gastroesophageal reflux disease.

Answer 144

**Correct Answer:** **A) Cavernous sinus** ### Explanation: - The **cavernous sinus** is a venous sinus located on either side of the sella turcica. It is vulnerable to **septic thrombosis** due to infections in the **"danger triangle"** of the face (nose, upper lip, and periorbital region) via emissary veins. - **Clinical features** (cavernous sinus thrombosis): - **Proptosis** (forward displacement of the eye) - **Chemosis** (conjunctival edema) - **Ophthalmoplegia** (CN III, IV, VI pass through the sinus) - **Periorbital edema** and **fever** - This is a **life-threatening emergency** requiring IV antibiotics and anticoagulation. **Why not the others?** - **B) Optic nerve**: Would cause visual loss (e.g., optic neuritis), not proptosis or chemosis. - **C) Pituitary gland**: Lesions cause hormonal dysfunction (e.g., bitemporal hemianopia if compressed). - **D) Superior sagittal sinus**: Thrombosis causes increased ICP/headache, not ocular symptoms. - **E) Trigeminal nerve**: Would cause facial sensory loss or trigeminal neuralgia.

Answer 145

**Correct Answer:** **B) Central retinal artery** ### Explanation: - The **central retinal artery** is a branch of the **ophthalmic artery** (which itself arises from the internal carotid artery). - It enters the orbit through the **optic canal** (along with the optic nerve) and supplies the **retina**. - **Amaurosis fugax** (transient monocular vision loss) is caused by **emboli** (often from carotid atherosclerosis) occluding this artery or its branches. - A **carotid bruit** suggests significant stenosis, requiring urgent evaluation (e.g., carotid Doppler, CTA/MRA). **Why not the others?** - **A) Ophthalmic artery**: The *parent vessel* of the central retinal artery, but it enters via the optic canal *before* branching. - **C) Lacrimal artery**: Supplies the lacrimal gland; branches off the ophthalmic artery *within* the orbit. - **D) Supraorbital artery**: Exits the orbit via the supraorbital foramen (not optic canal). - **E) Anterior ethmoidal artery**: Passes through the **anterior ethmoidal foramen** to supply nasal mucosa.

Answer 146

**Correct Answer:** **C) Vestibulocochlear (CN VIII)** ### Explanation: - The **cerebellopontine angle (CPA)** is a wedge-shaped space between the cerebellum, pons, and petrous temporal bone. - The **vestibulocochlear nerve (CN VIII)** is the most common origin of **CPA tumors**, specifically **vestibular schwannomas (acoustic neuromas)**. - **Clinical features**: - **Unilateral sensorineural hearing loss** (most common symptom) - **Tinnitus** - **Vertigo/imbalance** (less common early on) - **Facial numbness/weakness** (if large enough to compress CN V or VII) - Diagnosis: **MRI** (gold standard). **Why not the others?** - **A) Trigeminal (CN V)**: Schwannomas here are rare; would cause facial sensory loss, not hearing issues. - **B) Facial (CN VII)**: Can be compressed by a CPA tumor but is rarely the *primary* source. - **D) Glossopharyngeal (CN IX)**: Lesions cause glossopharyngeal neuralgia or dysphagia, not CPA syndrome. - **E) Hypoglossal (CN XII)**: Innervates the tongue; unrelated to CPA.

Answer 147

**Correct Answer:** **A) Anterior communicating artery** ### Explanation: - **Berry aneurysms** (saccular aneurysms) most commonly occur at **bifurcations** of arteries in the **Circle of Willis**. - The **anterior communicating artery (ACoA)** is the **most frequent site** (~30-35% of cases), followed by: - Posterior communicating artery (~25%) - Middle cerebral artery bifurcation (~20%) - **Subarachnoid hemorrhage (SAH)** classically presents with: - **Thunderclap headache** ("worst headache of life") - **Meningism** (neck stiffness, photophobia) - **Reduced consciousness** (if severe) - **Diagnosis:** Non-contrast CT head (95% sensitive in first 24 hours) → **CTA/DSA** for confirmation. **Why not the others?** - **B) Middle cerebral artery**: A common site but less frequent than ACoA. - **C) Posterior communicating artery**: Second most common location. - **D) Basilar artery**/**E) Vertebral artery**: More likely to cause **posterior circulation strokes** (e.g., locked-in syndrome).

Answer 148

**Correct Answer:** **C) Marginal mandibular branch of the facial nerve** ### Explanation: - The **marginal mandibular branch** of the **facial nerve (CN VII)** innervates the **depressor anguli oris** and **depressor labii inferioris** muscles, which lower the corner of the mouth. - **Injury during submandibular gland surgery** causes: - **Drooling** (inability to control saliva at the angle of the mouth). - **Asymmetrical smile** (ipsilateral lip fails to depress). - **Anatomical vulnerability**: This nerve runs superficially in the submandibular region, just deep to the platysma. The patient is drooling saliva because the depressor anguli oris has been paralysed due to damage of the marginal mandibular branch of the facial nerve. This is the most superficial nerve and can be damaged, if the skin incision is made incorrectly. To avoid damaging the nerve, a horizontal skin crease incision is made two fingers breadth below the ramus of the mandible, and the incision deepened down to the body of the gland. The superior flap consisting of the skin, platysma and fascia investing the gland is then lifted up to the ramus of the mandible. Damage to the nerve which lies between the platysma and the fascia is thus avoided **Why not the others?** - **A) Lingual nerve**: Causes **loss of taste** (anterior 2/3 tongue) and **numbness** of the tongue. - **B) Hypoglossal nerve**: Causes **tongue deviation** (as in Question 7). - **D) Glossopharyngeal nerve**: Unrelated to submandibular gland surgery; affects gag reflex/taste. - **E) Spinal accessory nerve**: Injured in neck dissections, causing **shoulder droop** (trapezius weakness).

Answer 149

**Correct Answer:** **B) External laryngeal nerve** ### Explanation: - The **external laryngeal nerve** (a branch of the **superior laryngeal nerve**, from the vagus nerve) runs **close to the superior thyroid artery** near the upper pole of the thyroid gland. - **Injury during thyroid surgery** causes: - **Weakness of the cricothyroid muscle** (which tenses the vocal cords). - **Fatiguing voice** (inability to sustain high-pitched sounds, e.g., singing). - **Why it’s at risk**: The nerve lies deep to the superior thyroid artery; ligating the artery too far from the gland risks entrapment. **Why not the others?** - **A) Recurrent laryngeal nerve**: At risk near the **inferior thyroid artery**; injury causes **hoarseness** (vocal cord paralysis). - **C) Vagus nerve**: Too proximal to be injured during thyroidectomy. - **D) Pharyngeal plexus**: Innervates pharyngeal muscles; injury causes dysphagia. - **E) Cervical sympathetic trunk**: Causes **Horner’s syndrome** (ptosis, miosis, anhidrosis) if damaged.

Answer 150

**Correct Answer:** **A) Trigeminal (CN V)** ### Explanation: - The **trigeminal nerve (CN V)** is the sensory nerve of the face and is the primary nerve involved in **trigeminal neuralgia**, a condition characterized by: - **Episodic, severe, stabbing pain** in one or more divisions of the nerve (most commonly **V2 (maxillary)** or **V3 (mandibular)**). - **Triggered by innocuous stimuli** (e.g., chewing, cold wind, shaving). - **Pathophysiology**: Often due to **vascular compression** of the trigeminal nerve root (e.g., by the superior cerebellar artery). - **Treatment**: First-line = **carbamazepine**; surgical options include microvascular decompression. **Why not the others?** - **B) Facial (CN VII)**: Motor nerve; lesions cause **facial palsy**, not pain. - **C) Glossopharyngeal (CN IX)**: Causes **glossopharyngeal neuralgia** (pain in throat/ear, triggered by swallowing). - **D) Vagus (CN X)**: Unrelated to facial pain. - **E) Hypoglossal (CN XII)**: Motor nerve to the tongue.

Answer 151

**Correct Answer:** **A) Vertebral artery** ### Explanation: - **Subclavian steal syndrome** occurs due to **stenosis/occlusion of the subclavian artery proximal to the vertebral artery origin**. - During arm exercise, blood is **"stolen" retrograde** from the **vertebral artery** (which normally supplies the brain) to perfuse the arm, causing: - **Vertebrobasilar insufficiency**: Dizziness, syncope, visual disturbances. - **Arm claudication**: Pain/fatigue with exertion. - **Diagnosis**: Reduced BP in the affected arm (>15 mmHg difference), **Doppler ultrasound** showing reversed vertebral flow. **Why not the others?** - **B) Internal thoracic artery**: Supplies anterior chest wall; not part of the steal phenomenon. - **C) Thyrocervical trunk/D) Costocervical trunk/E) Dorsal scapular artery**: Branches of the subclavian artery but do not contribute to collateral circulation in this syndrome.

Answer 152

**Correct Answer:** **A) Between thyropharyngeus and cricopharyngeus** ### Explanation: - **Killian’s dehiscence** is a natural anatomical weakness in the **inferior pharyngeal constrictor muscle**, specifically between: - **Thyropharyngeus** (oblique fibers, part of the inferior constrictor). - **Cricopharyngeus** (horizontal fibers, acts as the **upper esophageal sphincter**). - **Pharyngeal (Zenker’s) diverticulum** forms here due to **incoordination of swallowing** (cricopharyngeus fails to relax). - **Symptoms**: Dysphagia, regurgitation, halitosis, neck swelling. - **Treatment**: Cricopharyngeal myotomy ± diverticulectomy/diverticulopexy. The Killian’s dehiscence is a potential weakness between the cricopharyngeus (transverse fibres) and thyropharyngeus (oblique fibres) parts of the inferior constrictor muscle of the pharynx. It was first described by Gustav Killian, Director of Rhinolaryngological Clinic in Freiberg and Berlin. The inferior constrictor encloses the middle and superior constrictor muscles with its fibres, curving backwards and upwards around them. The cricopharyngeus is continuous with the circular muscle coat of the oesophagus and acts as a sphincter. It is always closed, relaxing only during deglutition. After excision of a pharyngeal pouch, cricopharyngeal myotomy is an essential part of the operation. **Why not the others?** - **B) Between superior/middle constrictors**: Rare site for diverticula. - **C) Palatopharyngeus muscles**: Part of the soft palate; unrelated. - **D) Esophageal fibers**: A distal site for **epiphrenic diverticula** (associated with achalasia). - **E) Middle/inferior constrictors**: No named dehiscence here.

Answer 153

**Correct Answer:** **C) Sternocleidomastoid (sternal and clavicular heads), clavicle** ### Explanation: - **Sedillot’s triangle** (also called the **sternocleidomastoid triangle**) is the landmark for **internal jugular vein (IJV) cannulation**. It is formed by: - **Sternal head of sternocleidomastoid (SCM)** (medially). - **Clavicular head of SCM** (laterally). - **Clavicle** (inferiorly). - The **IJV** lies within this triangle, lateral to the carotid artery. - **Ultrasound guidance** is now standard to avoid complications (e.g., arterial puncture, pneumothorax). **Why not the others?** - **A) Omohyoid** is part of the **subclavian triangle** (for supraclavicular brachial plexus block). - **B) Trapezius** forms the **posterior triangle** (contains accessory nerve). - **D) Anterior scalene**/**E) Posterior scalene**: Part of the **interscalene groove** (for brachial plexus blocks).

Answer 154

**Correct Answer:** **A) T1 sympathetic fibers** ### Explanation: - **Horner’s syndrome** (ptosis, miosis, anhydrosis) occurs due to interruption of the **sympathetic pathway** to the eye. - In **thoracoscopic sympathectomy**, the **T1 sympathetic ganglion** is often targeted for palmar hyperhidrosis. Damage to these fibers causes: - **Ptosis**: Loss of sympathetic input to Müller’s muscle (upper eyelid). - **Miosis**: Unopposed parasympathetic action (pupil constriction). - **Anhydrosis**: Lack of sweating on the ipsilateral face. - **Why T1?** The **ciliospinal center of Budge** (T1–T2) gives rise to preganglionic fibers ascending to the superior cervical ganglion. **Why not the others?** - **B) Phrenic nerve**: Causes **diaphragm paralysis** (ipsilateral raised hemidiaphragm on CXR). - **C) Vagus nerve**: Unrelated to Horner’s syndrome. - **D) Intercostobrachial nerve**: Sensory nerve; injury causes **medial arm numbness**. - **E) Long thoracic nerve**: Causes **winged scapula** (serratus anterior paralysis).

Answer 155

**Correct Answer:** **A) 3rd pharyngeal pouch** ### Explanation: - The **inferior parathyroid glands** originate from the **3rd pharyngeal pouch**, while the **superior parathyroids** arise from the **4th pharyngeal pouch**. - The **thymus** also develops from the 3rd pouch, explaining why inferior parathyroid adenomas may migrate into the **mediastinum** (along with thymic tissue). - **Sestamibi scan** localizes ectopic adenomas (e.g., retroesophageal, mediastinal). **Why not the others?** - **B) 4th pharyngeal pouch**: Gives rise to **superior parathyroids** (more constant in position). - **C) Ultimobranchial body**: Source of **parafollicular C-cells** (produce calcitonin). - **D) Thyroid diverticulum**: Forms the **thyroid gland** (from the floor of the pharynx). - **E) 2nd pharyngeal pouch**: Contributes to **palatine tonsils**.

Answer 156

**Correct Answer:** **B) Musculocutaneous nerve** ### Explanation: - The **lateral cord** of the brachial plexus (formed by **C5–C7 roots**) gives rise to: - **Musculocutaneous nerve** (supplies biceps brachii, brachialis, coracobrachialis; sensory to lateral forearm). - **Lateral pectoral nerve** (to pectoralis major). - **Contribution to the median nerve** (lateral root). - **Upper brachial plexus injury (Erb’s palsy)**: Affects **C5–C6**, causing "waiter’s tip" posture (arm adducted, internally rotated; forearm extended). **Why not the others?** - **A) Axillary nerve**/**C) Radial nerve**/**D) Thoracodorsal nerve**/**E) Upper subscapular nerve**: All are branches of the **posterior cord**.

Answer 157

**Correct Answer:** **B) Long thoracic nerve** ### Explanation: - The **long thoracic nerve** (arising from **C5–C7 roots**) innervates the **serratus anterior muscle**, which: - **Protracts the scapula** (e.g., pushing movements). - **Stabilizes the scapula** against the thoracic wall. - **Injury causes**: - **Winged scapula** (prominent medial border when pushing against resistance). - Weakness in arm abduction >90° (due to loss of scapular rotation). - **Common causes**: Trauma (e.g., mastectomy, blunt injury), viral illness, or idiopathic. **Why not the others?** - **A) Dorsal scapular nerve**: Supplies **rhomboids**; injury causes mild scapular winging. - **C) Suprascapular nerve**: Innervates **supraspinatus/infraspinatus**; injury causes weak shoulder abduction/external rotation. - **D) Thoracodorsal nerve**: Supplies **latissimus dorsi**; injury weakens arm adduction. - **E) Nerve to subclavius**: Minor motor nerve; injury is clinically silent.

Answer 158

**Correct Answer:** **D) Subscapularis** ### Explanation: - The **subscapularis muscle** is the **primary internal rotator** of the shoulder (along with teres major and pectoralis major). - **Injury causes**: - **Weakness in internal rotation** (e.g., inability to tuck in a shirt behind the back). - **Positive belly-press test** (patient pushes abdomen with hand; elbow drops back if subscapularis is weak). - Part of the **rotator cuff** (SITS muscles: Supraspinatus, Infraspinatus, Teres minor, Subscapularis). **Why not the others?** - **A) Supraspinatus**: Initiates abduction (first 15°); injured in **"painful arc" syndrome**. - **B) Infraspinatus**/**C) Teres minor**: External rotators; injury causes weak external rotation (e.g., **"hornblower’s sign"**). - **E) Teres major**: Not a rotator cuff muscle; assists internal rotation but is innervated by the **lower subscapular nerve**.

Answer 159

**Correct Answer:** **D) Radial nerve** ### Explanation: - The **radial nerve** is vulnerable in **humeral shaft fractures** (especially mid-shaft/spiral groove) because it runs in the **radial groove** directly against the bone. - **Injury causes**: - **Wrist drop** (inability to extend the wrist/fingers due to paralysis of extensor muscles). - **Sensory loss** over the **dorsal web space** (between thumb and index finger). - **Treatment**: Conservative (if neuropraxia) vs. surgical exploration (if nerve transection). **Why not the others?** - **A) Axillary nerve**: Injured in **shoulder dislocations**; causes deltoid weakness/loss of shoulder abduction. - **B) Median nerve**: Causes **"ape hand"** (thenar atrophy, loss of thumb opposition). - **C) Musculocutaneous nerve**: Weak elbow flexion (biceps/brachialis) + sensory loss over lateral forearm. - **E) Ulnar nerve**: Causes **claw hand** (intrinsic muscle paralysis) + sensory loss over medial 1.5 fingers.

Answer 160

**Correct Answer:** **E) Flexor carpi ulnaris** ### Explanation: - The **flexor carpi ulnaris (FCU)** is the **only forearm flexor innervated by the ulnar nerve** (not the median nerve). - **Median nerve innervates**: - **Pronator teres** (PT). - **Flexor carpi radialis** (FCR). - **Palmaris longus** (PL). - **Flexor digitorum superficialis** (FDS). - (Also: Lateral ½ of **flexor digitorum profundus**, **flexor pollicis longus**, **pronator quadratus**). - **Ulnar nerve’s role**: FCU + medial ½ of FDP (hence "ulnar paradox": clawing worsens with distal ulnar nerve lesions). **Why not the others?** All are median nerve-innervated: - **A) Flexor carpi radialis**/**B) Palmaris longus**/**C) Pronator teres**/**D) Flexor digitorum superficialis**.

Answer 161

The correct answer is: A) Internal thoracic artery Explanation: The internal thoracic artery (also known as the internal mammary artery) is the primary source of blood supply to the breast. It arises from the subclavian artery and runs down the inner aspect of the anterior chest wall, giving off perforating branches that supply the medial part of the breast. Other arteries contributing to breast vascularization include: • Lateral thoracic artery – supplies the lateral portion of the breast; a significant secondary contributor. • Thoracoacromial artery – gives minor contributions via its pectoral branch. • Posterior intercostal arteries – provide deep perforating branches. • Superior epigastric artery – has a minimal role and is not a primary contributor.

Answer 162

C. Between the sternal and clavicular heads of sternocleidomastoid Explanation: When inserting a central venous catheter into the internal jugular vein, the common anatomical landmark targeted is the triangle formed by the two heads of the sternocleidomastoid muscle (SCM) and the clavicle. This area is known as Sedillot’s triangle or the lesser supraclavicular fossa. The internal jugular vein lies just lateral to the carotid artery in this triangle, making it accessible for cannulation. It runs from the base of the skull, descends within the carotid sheath, and joins the subclavian vein behind the sternoclavicular joint to form the brachiocephalic vein. The anaesthetist is looking for the terminal part of the internal jugular vein which lies in the triangular gap between the sternal and clavicular heads of the sternocleidomastoid muscle. It joins the subclavian vein to form the brachiocephalic vein behind the sternal end of the clavicle. This anatomical knowledge is essential to help in the insertion of a central venous pressure cannula. The procedure can be facilitated by the use of ultrasound Doppler to localise precisely the site of venous puncture. The right side is most commonly used to insert a central venous pressure line as the approach is direct to the superior vena cava and there is no danger of damage to the thoracic duct, as on the left side. Other options: • A. Between angle of mandible and SCM – too high; not a typical access site. • B. Between trapezius and posterior border of SCM – this is the posterior triangle; not appropriate for IJV access. • D. Between SCM and posterior belly of digastric – location of upper IJV but not commonly used. • E. 1 cm lateral and 2 cm above SC joint – more indicative of subclavian vein access.

Answer 163

B 1st thoracic nerve During this operation the 1st thoracic nerve has been inadvertently damaged resulting in division of the sympathetic fibres which ultimately supply the smooth muscle part of the levator palpebrae superioris (Muller’s muscle). Paralysis of this part of the muscle causes partial ptosis. This is one of the features of Horner’s syndrome, the others being constriction of the pupil and absence of sweating in the forehead. The syndrome, described in 1869 by Johann Friedrich Horner (1831–1916), Professor of Ophthalmology in Zurich, can also occur from compression of the T1 nerve root by a space-occupying lesion such as a carcinoma of the apex of the lung, carcinoma of the thyroid or oesophagus, metastatic lymph nodes or pressure from thoracic inlet/outlet syndrome.

Answer 164

D) 3rd pharyngeal pouch Explanation: The parathyroid glands develop embryologically from the third and fourth pharyngeal pouches: • The third pharyngeal pouch gives rise to the inferior parathyroid glands and the thymus. • The fourth pharyngeal pouch gives rise to the superior parathyroid glands. Key embryological detail: Although the inferior parathyroids develop from a higher pouch (3rd) than the superior (4th), they descend further during development. As they descend with the thymus, they can end up in the superior mediastinum, which is a common ectopic location for a parathyroid adenoma derived from the 3rd pouch. Hence, a parathyroid adenoma found in the superior mediastinum most likely originates from the 3rd pharyngeal pouch.

Answer 165

The correct answer is E: Ultrasound of the abdomen Explanation: In a young patient with suspected appendicitis, ultrasound of the abdomen is the most appropriate initial investigation. It is non-invasive, does not involve radiation, and has good sensitivity and specificity for appendicitis. Ultrasound can visualize an inflamed appendix and exclude other pathologies such as ovarian cysts or ectopic pregnancy in female patients. CT scan would be considered if ultrasound is inconclusive or if there is suspicion of complications such as perforation or abscess formation.

Answer 166

The correct answer is D: Pancreatic adenocarcinoma Explanation: The clinical presentation of painless jaundice, weight loss, and steatorrhea in an elderly patient with a mass in the head of the pancreas is classic for pancreatic adenocarcinoma. Pancreatic cancer in the head of the pancreas causes obstruction of the common bile duct leading to jaundice, and obstruction of the pancreatic duct leading to steatorrhea (due to pancreatic exocrine insufficiency). The prognosis is generally poor, with a 5-year survival rate of less than 10%.

Answer 167

The correct answer is C: Hepatocellular carcinoma Explanation: The combination of a solid liver mass with markedly elevated alpha-fetoprotein (AFP) is highly suggestive of hepatocellular carcinoma (HCC). HCC typically occurs in patients with underlying liver disease, particularly cirrhosis due to hepatitis B, hepatitis C, or alcoholic liver disease. AFP is a tumor marker for HCC, and levels above 400 ng/mL are highly specific for this diagnosis. The clinical presentation of right upper quadrant pain, weight loss, and anorexia is consistent with advanced HCC.

Answer 168

The correct answer is E: Squamous cell carcinoma Explanation: Squamous cell carcinoma is the most common histological type in the mid-esophagus. Risk factors include smoking, alcohol consumption, and hot beverages. Adenocarcinoma is more common in the lower third of the esophagus and is associated with Barrett’s esophagus.

Answer 169

The correct answer is B: Ascending cholangitis Explanation: The clinical triad of right upper quadrant pain, fever, and jaundice (Charcot’s triad) is characteristic of ascending cholangitis. This is caused by obstruction of the common bile duct, usually by gallstones, leading to biliary stasis and bacterial infection. The ultrasound findings of gallstones and a dilated common bile duct support this diagnosis. Urgent decompression of the biliary tree is required, typically via endoscopic retrograde cholangiopancreatography (ERCP).

Answer 170

Thank you for your answer. The correct answer is B. Supination. Explanation: The proximal radioulnar joint is where the head of the radius articulates with the radial notch of the ulna. This joint, along with the distal radioulnar joint, allows for pronation and supination movements of the forearm. The annular ligament is a strong fibrous band that encircles the head of the radius and holds it in place against the radial notch of the ulna. When the proximal radioulnar joint is dislocated and the annular ligament is stretched (a condition sometimes called “nursemaid’s elbow” or “pulled elbow” in children), supination becomes particularly painful. This is because supination requires the head of the radius to rotate within the annular ligament, and when this ligament is injured, this movement causes pain. The other options are less directly affected by this specific injury: • Elbow flexion and extension primarily involve the humeroulnar joint • Shoulder abduction is unrelated to this injury • Radial deviation of the wrist involves the radiocarpal joint, not the proximal radioulnar joint

Answer 171

Thank you for your answer. The correct answer is E. Thoracodorsal. Explanation: The thoracodorsal nerve innervates the latissimus dorsi muscle, which is a powerful muscle that performs adduction, medial rotation, and extension of the arm. These movements are essential for the pulling phase of swimming strokes, especially in freestyle and butterfly. The latissimus dorsi is often called the “swimmer’s muscle” because of its importance in swimming. The thoracodorsal nerve runs through the axilla to reach the latissimus dorsi, making it vulnerable to injury from direct trauma to the axilla, as described in this scenario with the bike handlebar. When this nerve is damaged, the latissimus dorsi becomes weak, significantly affecting swimming performance. The other options are incorrect because: • Accessory nerve: Innervates the trapezius and sternocleidomastoid muscles • Dorsal scapular nerve: Innervates the rhomboid muscles and levator scapulae • Lateral pectoral nerve: Innervates the pectoralis major muscle • Medial pectoral nerve: Innervates the pectoralis major and minor muscles