Anatomy

Question 1

What are the 3 successive kidney systems involved in renal development?

Answer 1

Pronephros, mesonephros, and metanephros.

Question 2

What is the hepatic portal system?

Answer 2

An extensive network of veins that receives blood flow from the GI tract above the pectinate line.

Question 3

How is venous flow from the GI tract carried to the liver?

Answer 3

Via the hepatic portal vein.

Question 4

Where does the blood go after entering the liver sinusoids?

Answer 4

It drains into the hepatic veins.

Question 5

Where do the hepatic veins drain?

Answer 5

Into the inferior vena cava and ultimately into the right atrium.

Question 6

What forms the hepatic portal vein?

Answer 6

The union of the superior mesenteric vein (drains midgut) and splenic vein (drains foregut) posterior to the neck of the pancreas.

Question 7

Where does the inferior mesenteric vein usually drain?

Answer 7

Into the splenic vein.

Question 8

What can compress the left renal vein?

Answer 8

An aneurysm of the superior mesenteric artery as the vein crosses anterior to the aorta.

Question 9

What symptoms may result from compression of the left renal vein?

Answer 9

Renal and adrenal hypertension on the left, and in males, a varicocele on the left.

Question 10

Most common site of bowel ischemia.

Answer 10

The splenic flexure.

Question 11

Abdominal aorta visceral branches (unpaired and paired).

Answer 11

Unpaired: celiac (foregut), superior mesenteric (midgut), inferior mesenteric (hindgut).

Paired: middle suprarenals, renals, gonadals.

Question 12

Abdominal aorta parietal branches (unpaired and paired).

Answer 12

Unpaired: median sacral.

Paired: inferior phrenics, lumbars, common iliac.

Question 13

Most common site for an abdominal aneurysm.

Answer 13

Between the renal arteries and the bifurcation of the abdominal aorta.

Question 14

Signs of an abdominal aneurysm.

Answer 14

Decreased circulation to the lower limbs and pain radiating down the back of the lower limbs.

Question 15

Most common site of atherosclerotic plaque.

Answer 15

At the bifurcation of the abdominal aorta.

Question 16

What are the branches of the celiac artery?

Answer 16

Left gastric artery, common hepatic artery, splenic artery.

Question 17

What is the longest branch of the celiac trunk and its course?

Answer 17

The splenic artery, which runs a tortuous course along the superior border of the pancreas and is retroperitoneal until it reaches the tail of the pancreas.

Question 18

What are the distributions of the splenic artery?

Answer 18

• Direct branches to the spleen.
• Direct branches to the neck, body, and tail of the pancreas.
• Left gastroepiploic artery (supplies the left side of the greater curvature of the stomach).
• Short gastric branches (supply the fundus of the stomach).

Question 19

What are the two terminal branches of the common hepatic artery?

Answer 19

Proper hepatic artery and gastroduodenal artery.

Question 20

What does the proper hepatic artery do?

Answer 20

It ascends within the hepatoduodenal ligament to the porta hepatis, where it divides into the right and left hepatic arteries. The right hepatic artery gives rise to the cystic artery to the gallbladder.

Question 21

What does the gastroduodenal artery do?

Answer 21

It descends posterior to the first part of the duodenum and divides into the right gastroepiploic artery (supplies the pyloric end of the greater curvature of the stomach) and the superior pancreaticoduodenal arteries (supplies the head of the pancreas and anastomoses with the inferior pancreaticoduodenal branches of the superior mesenteric artery).

Question 22

What artery may be subject to erosion by a penetrating ulcer of the posterior wall of the stomach into the lesser sac?

Answer 22

The splenic artery.

Question 23

What artery may be subject to erosion by a penetrating ulcer of the lesser curvature of the stomach?

Answer 23

The left gastric artery.

Question 24

What artery may be subject to erosion by a penetrating ulcer of the posterior wall of the first part of the duodenum?

Answer 24

The gastroduodenal artery.

Question 25

Main functions of bile.

Answer 25

* Absorption of fats from intestinal lumen * Excretion * Transport of IgA

Question 26

What is the largest visceral organ and gland in the body?

Answer 26

The liver.

Question 27

What are hepatocytes and what functions do they carry out?

Answer 27

Hepatocytes are of endodermal epithelial origin and carry out both exocrine and endocrine functions.

Question 28

What are hepatic sinusoids and what do they facilitate?

Answer 28

Hepatic sinusoids are unusual capillaries that facilitate exchange (uptake and secretion) between hepatocytes and blood.

Question 29

What are Kupffer cells and what is their role?

Answer 29

Kupffer cells are specialized cells of the mononuclear phagocyte system (blood monocyte derived) that patrol the space of Disse between hepatocytes and blood.

Question 30

What are bile ducts and what do they do?

Answer 30

Bile ducts are epithelial-lined exocrine ducts that drain hepatocyte products (bile) into the duodenum via the common bile duct.

Question 31

How is blood flow into and out of the liver?

Answer 31

Blood flow into the liver is dual (75% from the portal vein, 25% from the hepatic artery), while blood flow out is via the hepatic veins into the inferior vena cava.

Question 32

How are hepatocytes functionally polarized?

Answer 32

Hepatocytes are functionally polarized with multiple "basal" and "apical" surfaces, rather than along a single axis.

Question 33

What forms bile canaliculi between two hepatocytes?

Answer 33

Where two hepatocytes abut, their "apical" surfaces form bile canaliculi, which are extracellular grooved bile channels joined by tight and occluding junctions.

Question 34

What happens to bile secreted into bile canaliculi?

Answer 34

Bile is secreted into bile canaliculi, which drains into progressively larger bile ducts and empties into the duodenum.

Question 35

What surface do hepatocytes have where they abut a sinusoid?

Answer 35

Where a hepatocyte abuts a sinusoid, its membrane has microvilli, representing a "basal" or basolateral surface.

Question 36

How is exchange between blood and hepatocytes facilitated?

Answer 36

Exchange is facilitated by the surface microvilli in the space of Disse, which is between the fenestrated endothelial cells of the sinusoid and the basal surface of hepatocytes.

Question 37

Where do the hepatic artery, portal vein, and common hepatic duct enter and exit the liver?

Answer 37

They enter and exit the liver at the hepatic hilum.

Question 38

What is formed when branches of the hepatic artery, portal vein, and bile duct run together?

Answer 38

They form a portal triad (or portal tract) within thin connective tissue bands.

Question 39

How does blood flow through the liver?

Answer 39

Blood from both the portal vein and hepatic artery branches flows through and mixes in hepatic sinusoids, which run between cords or plates of hepatocytes.

Question 40

Where does blood from the sinusoids flow after passing by hepatocytes?

Answer 40

It flows into hepatic venules, which form progressively larger branches draining into the right and left hepatic veins, which then drain into the inferior vena cava.

Question 41

What is the portal triad?

Answer 41

It is the grouping of the hepatic artery, portal vein, and bile duct within connective tissue.

Question 42

What is a classic hepatic lobule?

Answer 42

It is a hexagonal structure with a portal tract at each corner and a central vein in the center.

Question 43

What is the direction of blood and bile flow in a hepatic lobule?

Answer 43

Blood flows from the triads into the central vein, while bile flows opposite, from the central vein to the triads.

Question 44

What is a portal lobule?

Answer 44

It is a triangular structure with central veins at each corner and a portal tract in the center.

Question 45

What is the direction of bile flow in a portal lobule?

Answer 45

Bile flows from the periphery of the portal lobule into the central triad.

Question 46

What is a hepatic acinus?

Answer 46

It is based on blood flow from hepatic artery branches to central veins, forming a roughly elliptical structure with portal tracts at the furthest poles and central veins at the closest edges.

Question 47

How is blood flow structured in a hepatic acinus?

Answer 47

Hepatic arterial blood flow enters the sinusoids from branches extending away from the center of the hepatic triad, not directly from the triad.

Question 48

What are Ito cells (stellate cells)?

Answer 48

They are mesenchymal cells located in the space of Disse, involved in storing fat and fat-soluble vitamins, mainly vitamin A.

Question 49

What are the functions of bile formation by hepatocytes?

Answer 49

Bile formation serves both an exocrine function (fat emulsification and absorption) and an excretory function (excretion of bilirubin and drug metabolites).

Question 50

What do Ito cells release during liver injury?

Answer 50

They may release type I collagen and other matrix components into the space of Disse, contributing to liver scarring.

Question 51

What liver complications can result from Ito cell activation?

Answer 51

It can lead to portal hypertension, portacaval anastomoses, and esophageal or rectal bleeding.

Question 52

What happens to Ito cells during liver injury?

Answer 52

When stimulated during liver injury, Ito cells may release type I collagen and other extracellular matrix components into the space of Disse. This contributes to fibrosis and scarring of the liver, a key factor in the development of cirrhosis, particularly due to ethanol consumption. As the liver becomes scarred, it can lead to the development of portal hypertension, which increases pressure in the portal venous system. This can cause the formation of portacaval anastomoses and result in complications such as esophageal or rectal bleeding.

Question 53

What type of epithelium lines the gallbladder, and what are its functions? What are the unique features of the gallbladder compared to the gut tube?

Answer 53

The gallbladder is lined by simple columnar epithelium with both absorptive and mucin-secretory functions, supported by an underlying lamina propria. Unlike the gut tube, the gallbladder lacks muscularis mucosae and submucosa. Its muscularis externa is not organized into two distinct layers like the gut.

Question 54

What are the anatomical features of the gallbladder and its ducts?

Answer 54

The gallbladder has a wide end called the fundus and a narrowing neck. The neck empties into the cystic duct, which contains spiral valves of Heister. The cystic duct joins the common hepatic duct to form the common bile duct. This common bile duct then joins the pancreatic duct at or just before the ampulla of Vater.

Question 55

What is the indifferent gonad stage in development?

Answer 55

Although sex is determined at fertilization, the gonads initially go through an indifferent stage between weeks 4–7, during which there are no specific ovarian or testicular characteristics. The indifferent gonads develop in a longitudinal elevation or ridge of intermediate mesoderm called the urogenital ridge.

Question 56

Components of the indifferent gonads:

Answer 56

- Primordial germ cells provide a critical inductive influence on gonad development and migrate in at week 4. They arise from the lining cells in the wall of the yolk sac. - Primary sex cords are finger-like extensions of the surface epithelium that grow into the gonad and are populated by the migrating primordial germ cells. - Mesonephric (Wolffian) and paramesonephric (Müllerian) ducts of the indifferent gonad contribute to the male and female genital tracts, respectively.

Question 57

Testis and Ovary Development:

Answer 57

The indifferent gonad develops into either the testis or ovary, depending on the genetic and hormonal factors involved.

Question 58

Factors influencing testis development:

Answer 58

- Sry gene on the short arm of the Y chromosome, which encodes for testis-determining factor (TDF) - Testosterone, secreted by the Leydig cells - Müllerian-inhibiting factor (MIF), secreted by the Sertoli cells - Dihydrotestosterone (DHT): responsible for the development of external genitalia

Question 59

Factors influencing ovary development:

Answer 59

Ovary and female reproductive system development requires estrogen. Ovarian development occurs in the absence of the Sry gene and in the presence of the WNT4 gene.

Question 60

Meiosis:

Answer 60

Meiosis is a specialized process of cell division that occurs in the testis and ovary to produce male gametes (spermatogenesis) and female gametes (oogenesis). There are notable differences between spermatogenesis and oogenesis.

Question 61

Meiosis I:

Answer 61

- Synapsis: Pairing of 46 homologous chromosomes - Crossing over: Exchange of segments of DNA between homologous chromosomes - Disjunction: Separation of the 46 homologous chromosome pairs (without centromere-splitting) into 2 daughter cells, each containing 23 chromosome pairs

Question 62

Meiosis II:

Answer 62

- Synapsis does not occur, nor does crossing over - Disjunction occurs with centromere-splitting, resulting in the separation of sister chromatids into two daughter cells.

Question 63

What is spermatogenesis, and where does it occur?

Answer 63

Spermatogenesis is the process of male gamete (sperm) production, occurring in the testes. It involves the differentiation of primordial germ cells into mature spermatozoa.

Question 64

Describe the stages of spermatogenesis.

Answer 64

Spermatogenesis begins with primordial germ cells differentiating into type A spermatogonia. These type A spermatogonia differentiate into type B spermatogonia, which then enter meiosis I to form primary spermatocytes. Primary spermatocytes undergo meiosis I to form secondary spermatocytes, which undergo meiosis II to form spermatids. Spermatids then undergo spermiogenesis, becoming mature spermatozoa.

Question 65

What is the role of the Sertoli cells during spermatogenesis?

Answer 65

Sertoli cells provide structural and nutritional support to the developing sperm during spermatogenesis, and they also secrete Müllerian-inhibiting factor (MIF) to prevent the development of female reproductive structures.

Question 66

What is the function of testosterone in male development?

Answer 66

Testosterone, secreted by Leydig cells, is crucial for the development of male reproductive organs and external genitalia, and it is necessary for spermatogenesis.

Question 67

What is the process of oogenesis during fetal development?

Answer 67

Primordial germ cells differentiate into oogonia, which then enter meiosis I to form primary oocytes. All primary oocytes are formed by the fifth month of fetal life and are arrested in prophase of meiosis I until puberty.

Question 68

What happens to primary oocytes at puberty?

Answer 68

During each menstrual cycle, a primary oocyte becomes unarrested, completes meiosis I, and forms a secondary oocyte and a polar body.

Question 69

When does the secondary oocyte complete meiosis?

Answer 69

The secondary oocyte is arrested in metaphase of meiosis II and only completes meiosis II at fertilization, forming a mature oocyte and a polar body.

Question 70

What happens during fertilization in the ampulla of the uterine tube?

Answer 70

Fertilization occurs when the male and female pronuclei fuse to form a zygote.

Question 71

What does the secondary oocyte do at fertilization?

Answer 71

The secondary oocyte rapidly completes meiosis II.

Question 72

What are the two key changes spermatozoa undergo in the female genital tract prior to fertilization?

Answer 72

Spermatozoa undergo capacitation (removal of proteins from the acrosomal membrane) and release hydrolytic enzymes to penetrate the zona pellucida.

Question 73

What does capacitation in spermatozoa enable?

Answer 73

Capacitation enables sperm to penetrate the zona pellucida during fertilization.

Question 74

How does the cortical reaction prevent polyspermy?

Answer 74

The cortical reaction prevents polyspermy by blocking other sperm from entering the zona pellucida after the first sperm has fertilized the egg.

Question 75

What is the role of the trophoblast by the end of week 1?

Answer 75

By the end of week 1, the trophoblast differentiates into the cytotrophoblast and syncytiotrophoblast, marking the beginning of implantation.

Question 76

What are the risk factors and clinical signs of a tubal ectopic pregnancy?

Answer 76

Tubal ectopic pregnancy, the most common form, occurs when the blastocyst implants in the ampulla of the fallopian tube due to delayed transport. Risk factors include endometriosis, pelvic inflammatory disease, tubal pelvic surgery, and exposure to diethylstilbestrol (DES). Clinical signs include abnormal or brisk uterine bleeding, sudden onset of abdominal pain that may be confused with appendicitis, missed menstrual period (e.g., LMP 60 days ago), positive human chorionic gonadotropin test, culdocentesis showing intraperitoneal blood, and a positive sonogram.

Question 77

What is required for implantation to occur, and where does it usually happen?

Answer 77

For implantation to occur, the zona pellucida must degenerate. The blastocyst typically implants within the posterior wall of the uterus, with the embryonic pole of the blastocyst implanting first. Implantation occurs within the functional layer of the endometrium during the progestational phase of the menstrual cycle.

Question 78

What happens during week 2 in the formation of the bilaminar embryo?

Answer 78

In week 2, the embryoblast differentiates into the epiblast and hypoblast, forming a bilaminar embryonic disk. The epiblast forms the amniotic cavity, while hypoblast cells migrate to form the primary yolk sac. The prechordal plate, formed from the fusion of epiblast and hypoblast cells, is the site of the future mouth.

Question 79

What structures are formed by the extraembryonic somatic mesoderm during early development?

Answer 79

The extraembryonic somatic mesoderm forms the cytotrophoblast, the connecting stalk, and covers the amnion.

Question 80

What is the function of the syncytiotrophoblast during implantation, and how does it differ from the cytotrophoblast?

Answer 80

The syncytiotrophoblast continues to grow into the endometrium to make contact with endometrial blood vessels and glands but does not undergo mitosis. In contrast, the cytotrophoblast is mitotically active.

Question 81

What is the role of human chorionic gonadotropin (hCG) during pregnancy?

Answer 81

hCG stimulates progesterone production by the corpus luteum, which is essential for maintaining pregnancy.

Question 82

What can low and high levels of human chorionic gonadotropin (hCG) indicate?

Answer 82

Low hCG levels may predict a spontaneous abortion or ectopic pregnancy, while high hCG levels may indicate a multiple pregnancy, hydatidiform mole, or gestational trophoblastic disease.

Question 83

What major events occur during the embryonic period (weeks 3–8)?

Answer 83

All major organ systems begin to develop, and by the end of the period, the embryo starts to look human. The nervous and cardiovascular systems begin to develop, and gastrulation occurs, producing the three primary germ layers: ectoderm, mesoderm, and endoderm.

Question 84

What is gastrulation and what does it produce?

Answer 84

Gastrulation is the process by which the three primary germ layers—ectoderm, mesoderm, and endoderm—are produced. It begins with the formation of the primitive streak within the epiblast.

Question 85

What does the ectoderm form during the embryonic period?

Answer 85

The ectoderm forms neuroectoderm and neural crest cells.

Question 86

What structures does the mesoderm form?

Answer 86

The mesoderm forms paraxial mesoderm (which gives rise to 35 pairs of somites), intermediate mesoderm, and lateral mesoderm.

Question 87

What is a sacrococcygeal teratoma?

Answer 87

A tumor arising from remnants of the primitive streak, often containing tissues like bone, nerve, and hair.

Question 88

What is a chordoma, and where is it commonly found?

Answer 88

A tumor arising from remnants of the notochord, commonly found intracranially or in the sacral region.

Question 89

What is a hydatidiform mole, and what are its types?

Answer 89

A condition where the trophoblast is replaced by dilated villi. Complete mole: No embryo, karyotype 46,XX with chromosomes of paternal origin. Partial mole: Karyotype 69,XXY with one maternal haploid set and two paternal sets.

Question 90

What are the clinical implications of molar pregnancies?

Answer 90

Molar pregnancies have high hCG levels, and 20% can develop into malignant trophoblastic disease, such as choriocarcinoma.

Question 91

Ectoderm What structures are derived from surface ectoderm?

Answer 91

Epidermis, hair, nails, inner ear, external ear, enamel of teeth, lens of the eye, anterior pituitary (Rathke's pouch), parotid gland, anal canal below the pectinate line.

Question 92

Ectoderm What structures are derived from neuroectoderm?

Answer 92

Neural tube, central nervous system, retina and optic nerve, pineal gland, neurohypophysis, astrocytes, oligodendrocytes.

Question 93

Ectoderm What structures are derived from neural crest ectoderm?

Answer 93

Adrenal medulla, ganglia (sensory pseudounipolar neurons and autonomic postganglionic neurons), pigment cells, Schwann cells, meninges (pia and arachnoid mater), pharyngeal arch cartilage, odontoblasts, parafollicular (C) cells, aorticopulmonary septum, endocardial cushions.

Question 94

Mesoderm 4. What types of muscle are derived from mesoderm?

Answer 94

Smooth, cardiac, and skeletal muscle.

Question 95

Mesoderm What structures are formed by connective tissue derived from mesoderm?

Answer 95

Bone and cartilage, blood, lymph, cardiovascular organs, adrenal cortex, gonads, and internal reproductive organs.

Question 96

Mesoderm Which organs and structures come from paraxial mesoderm?

Answer 96

Somites, forming bone, muscle, and dermis.

Question 97

What does the notochord give rise to?

Answer 97

Nucleus pulposus of intervertebral discs.

Question 98

Endoderm 8. What epithelial linings are derived from the endoderm?

Answer 98

- GI tract: foregut, midgut, and hindgut. - Lower respiratory system: larynx, trachea, bronchi, and lungs. - Genitourinary system: urinary bladder, urethra, and lower vagina.

Question 99

Endoderm What parenchymal organs are derived from the endoderm?

Answer 99

Liver, pancreas, submandibular and sublingual glands, follicles of the thyroid gland.

Question 100

Endoderm What pharyngeal pouch derivatives come from the endoderm?

Answer 100

Auditory tube and middle ear, palatine tonsils, parathyroid glands, and thymus.

Question 101

Extraembryonic Structures 11. What are yolk sac derivatives?

Answer 101

Primordial germ cells, early blood cells, and blood vessels.

Question 102

What is the genotype in female pseudointersexuality?

Answer 102

46,XX.

Question 103

What tissue is present in individuals with female pseudointersexuality?

Answer 103

Ovarian tissue (no testicular tissue) and masculinization of the female external genitalia.

Question 104

What is the most common cause of female pseudointersexuality?

Answer 104

Congenital adrenal hyperplasia, leading to excess androgen production in the fetus.

Question 105

What is the genotype in male pseudointersexuality?

Answer 105

46,XY

Question 106

What tissue is present in individuals with male pseudointersexuality?

Answer 106

Testicular tissue (no ovarian tissue) and stunted development of the male external genitalia.

Question 107

What is the most common cause of male pseudointersexuality?

Answer 107

5α-reductase deficiency, leading to inadequate production of dihydrotestosterone.

Question 108

What causes 5α-reductase 2 deficiency?

Answer 108

A mutation in the 5α-reductase 2 gene that makes the enzyme underactive in converting testosterone to dihydrotestosterone (DHT).

Question 109

What are the clinical findings in 5α-reductase 2 deficiency?

Answer 109

Underdevelopment of the penis and emission of sperm (microphallus, hypospadias, bifid scrotum) and prostate. The epididymis, ductus deferens, seminal vesicle, and ejaculatory duct are normal.

Question 110

What happens during puberty in patients with 5α-reductase 2 deficiency?

Answer 110

They undergo virilization due to an increased testosterone-to-DHT ratio.

Question 111

What is the genotype and phenotype in Complete Androgen Insensitivity Syndrome?

Answer 111

46,XY genotype with testes and female external genitalia, including a rudimentary vagina; the uterus and uterine tubes are generally absent.

Question 112

Where are the testes typically located in Complete Androgen Insensitivity Syndrome, and what is the treatment?

Answer 112

The testes are often found in the labia majora and are surgically removed to prevent malignant tumor formation.

Question 113

How do individuals with Complete Androgen Insensitivity Syndrome present?

Answer 113

They appear as normal females, and their psychosocial orientation is typically female despite their 46,XY genotype.

Question 114

What is the most common cause of Complete Androgen Insensitivity Syndrome?

Answer 114

A mutation in the androgen receptor (AR) gene that renders the receptor inactive.

Question 115

What is another name for Complete Androgen Insensitivity Syndrome?

Answer 115

Testicular feminization syndrome.

Question 116

What is hypospadias?

Answer 116

It occurs when the urethral folds fail to fuse completely, causing the external urethral orifice to open onto the ventral surface of the penis.

Question 117

What condition is often associated with hypospadias?

Answer 117

A poorly developed penis that curves ventrally, known as chordee.

Question 118

What is epispadias?

Answer 118

It occurs when the external urethral orifice opens onto the dorsal surface of the penis.

Question 119

What condition is often associated with epispadias?

Answer 119

Exstrophy of the bladder.

Question 120

What is cryptorchidism (undescended testes)?

Answer 120

It occurs when the testes fail to descend into the scrotum, a process that normally happens within 3 months after birth.

Question 121

What are the consequences of bilateral cryptorchidism?

Answer 121

It results in sterility.

Question 122

Where are undescended testes typically located?

Answer 122

In the abdominal cavity or the inguinal canal.

Question 123

What is hydrocele of the testes?

Answer 123

It occurs when a small patency of the processus vaginalis allows peritoneal fluid to flow into the processus vaginalis, forming a fluid-filled cyst near the testes.

Question 124

What are the pelvic and urogenital diaphragms?

Answer 124

Two important skeletal muscle diaphragms that support pelvic and perineal structures, both innervated by branches of the pudendal nerve.

Question 125

What is the pelvic diaphragm, and what does it do?

Answer 125

It forms the muscular floor of the pelvis, separates the pelvic cavity from the perineum, supports pelvic organs, and transmits distal parts of the genitourinary and GI systems to the perineum.

Question 126

What muscles and fascia form the pelvic diaphragm?

Answer 126

The levator ani muscle, coccygeus muscle, and two layers of fascia.

Question 127

What is the role of the puborectalis component of the levator ani muscle?

Answer 127

It forms a muscular sling around the anorectal junction, marking the boundary between the rectum and anal canal, and is crucial for fecal continence.

Question 128

Where is the urogenital diaphragm located?

Answer 128

In the perineum, inferior to the pelvic diaphragm.

Question 129

What muscles form the urogenital diaphragm?

Answer 129

The sphincter urethrae and deep transverse perineus muscles, which extend horizontally between the two ischiopubic rami.

Question 130

What structures penetrate the urogenital diaphragm?

Answer 130

The urethra in males, and the urethra and vagina in females.

Question 131

What is the function of the sphincter urethrae muscle?

Answer 131

It acts as an external urethral sphincter, a voluntary muscle of micturition, surrounding the membranous urethra to maintain urinary continence.

Question 132

What happens in hyperplasia of the prostate?

Answer 132

An enlarged prostate gland compresses the urethra.

Question 133

What symptoms might a patient with hyperplasia of the prostate experience?

Answer 133

The patient will complain of frequent urges to urinate and difficulty starting urination.

Question 134

Why does hypertrophy of the prostate compress the urethra?

Answer 134

Because the prostate gland is enclosed in a dense connective tissue capsule, hypertrophy compresses the prostatic portion of the urethra.

Question 135

Where does the ureter course in relation to the suspensory ligament of the ovary, and why must it be protected?

Answer 135

The ureter courses just medial to the suspensory ligament of the ovary and must be protected when ligating the ovarian vessels.

Question 136

What structures provide support for the pelvic viscera?

Answer 136

The pelvic and urogenital diaphragms, perineal membrane, perineal body, and transverse (cardinal) cervical and uterosacral ligaments.

Question 137

What can result from weakness of support structures for the pelvic viscera?

Answer 137

Prolapse of the uterus into the vagina or herniation of the bladder or rectum into the vagina.

Question 138

Where does the ureter pass in relation to the uterine artery, and why must it be avoided during surgical procedures?

Answer 138

The ureter passes inferior to the uterine artery, 1 to 2 centimeters from the cervix ("water under the bridge"), and must be avoided during surgical procedures.

Question 139

What is the perineum, and where is it located?

Answer 139

The perineum is the diamond-shaped outlet of the pelvis located below the pelvic diaphragm.

Question 140

How is the perineum divided?

Answer 140

It is divided by a transverse line between the ischial tuberosities into the anal and urogenital triangles.

Question 141

What provides sensory and motor innervation to the perineum?

Answer 141

The pudendal nerve (S2, 3, 4) of the sacral plexus.

Question 142

What supplies the perineum with blood?

Answer 142

The internal pudendal artery, a branch of the internal iliac artery.

Question 143

Where do the pudendal nerve and vessels cross to enter the perineum?

Answer 143

They cross the ischial spine posteriorly to enter the perineum.

Question 144

What is located in the anal triangle?

Answer 144

The anal triangle is posterior and contains the anal canal surrounded by the fat-filled ischioanal fossa.

Question 145

What muscles guard the anal canal?

Answer 145

The anal canal is guarded by a smooth-muscle internal anal sphincter, innervated by the ANS, and an external anal sphincter, composed of skeletal muscle and innervated by the pudendal nerve.

Question 146

Where is the pudendal canal located, and what does it transmit?

Answer 146

The pudendal canal is found on the lateral aspect of the ischioanal fossa and transmits the pudendal nerve and internal pudendal vessels.

Question 147

Where is a pudendal nerve block performed to anesthetize the perineum?

Answer 147

A pudendal nerve block is performed as the pudendal nerve crosses posterior to the ischial spine.

Question 148

What is the urogenital triangle, and what does it contain?

Answer 148

The urogenital triangle forms the anterior aspect of the perineum and contains the superficial and root structures of the external genitalia.

Question 149

How is the urogenital triangle divided?

Answer 149

It is divided into superficial and deep perineal spaces (pouches).

Question 150

Where is the superficial perineal pouch located?

Answer 150

It is located between the perineal membrane of the urogenital diaphragm and the superficial perineal (Colles') fascia.

Question 151

What structures are found in the superficial perineal pouch?

Answer 151

The pouch contains: - Crura of the penis or clitoris (erectile tissue) - Bulb of the penis (in males) (erectile tissue; contains urethra) - Bulbs of the vestibule (in females) (erectile tissue in the lateral walls of the vestibule) - Ischiocavernosus muscle (skeletal muscle covering the crura of the penis or clitoris) - Bulbospongiosus muscle (skeletal muscle covering the bulb of the penis or bulb of the vestibule) - Greater vestibular (Bartholin) gland (in females only; homologous to Cowper's gland)

Question 152

What is the deep perineal pouch formed by?

Answer 152

The deep perineal pouch is formed by the fasciae and muscles of the urogenital diaphragm.

Question 153

What structures are found in the deep perineal pouch?

Answer 153

The pouch contains: - Sphincter urethrae muscle (serves as the voluntary external sphincter of the urethra) - Deep transverse perineal muscle - Bulbourethral (Cowper) gland (in males only; duct enters the bulbar urethra)

Question 154

Where are the bulbourethral (Cowper) glands located in males?

Answer 154

The bulbourethral (Cowper) glands are located in the deep perineal pouch of the male.

Question 155

Where are the greater vestibular (Bartholin) glands located in females?

Answer 155

The greater vestibular (Bartholin) glands are located in the superficial perineal pouch of the female.

Question 156

What is the crura of the penis continuous with?

Answer 156

The crura of the penis are continuous with the corpora cavernosa of the penis.

Question 157

What is the bulb of the penis continuous with?

Answer 157

The bulb of the penis is continuous with the corpus spongiosus of the penis (contains urethra).

Question 158

What structures form the shaft of the penis?

Answer 158

The corpora cavernosa and corpus spongiosus form the shaft of the penis.

Question 159

What can result from injury to the bulb of the penis in males?

Answer 159

Injury to the bulb of the penis may result in extravasation of urine from the urethra into the superficial perineal space. From this space, urine may pass into the scrotum, penis, and onto the anterior abdominal wall in the plane deep to Scarpa fascia.

Question 160

What are the crura of the clitoris continuous with?

Answer 160

The crura of the clitoris are continuous with the corpora cavernosa of the clitoris.

Question 161

Where are the bulbs of the vestibule located in relation to the vestibule?

Answer 161

The bulbs of the vestibule are separated from the vestibule by the labia minora.

Question 162

Where do the urethra and vagina empty in females?

Answer 162

The urethra and vagina empty into the vestibule.

Question 163

Where does the duct of the greater vestibular glands enter in females?

Answer 163

The duct of the greater vestibular glands enters the vestibule.

Question 164

Which muscles and areas are innervated by the pudendal nerve (S2, S3, S4 ventral rami)?

Answer 164

The pudendal nerve and its branches innervate the skeletal muscles in the pelvic and urogenital diaphragms, the external anal sphincter and sphincter urethrae, skeletal muscles in both perineal pouches, and the skin that overlies the perineum.

Question 165

What surrounds the testis and what is its role?

Answer 165

The testis is surrounded by a dense fibrous capsule called the tunica albuginea. The tunica albuginea is continuous with many of the interlobular septa that divide the testis into approximately 250 pyramidal compartments (testicular lobules).

Question 166

What structures are found within each testicular lobule?

Answer 166

Within each lobule are 1-4 seminiferous tubules, where spermatozoa are produced. Each tubule is a coiled, non-branching closed loop that is 150–200 µm in diameter and 30–70 cm in length. Both ends of each tubule converge on the rete testes.

Question 167

What cells and structures are found in the seminiferous tubules?

Answer 167

The seminiferous tubules contain spermatogenic cells, Sertoli cells, and a well-defined basal lamina.

Question 168

What forms the blood–testis barrier and what is its function?

Answer 168

The blood–testis barrier is formed by tight junctions between Sertoli cells and protects primary spermatocytes and their progeny.

Question 169

What is the process of spermatogenesis and how do spermatogenic cells develop?

Answer 169

Spermatogenic cells (germinal epithelium) are stacked in 4 to 8 layers between the basement membrane and the lumen of the seminiferous tubule. Stem cells (spermatogonia) are adjacent to the basement membrane. At puberty, spermatogonia resume mitosis, producing more stem cells and differentiated spermatogonia (types A and B). Type B spermatogonia differentiate into primary spermatocytes, which enter meiosis. Primary spermatocytes undergo the first meiotic division to form secondary spermatocytes, which rapidly undergo the second meiotic division to produce spermatids. The progeny of a single spermatogonium remain connected by cytoplasmic bridges throughout their differentiation into mature sperm.

Question 170

Spermiogenesis

Answer 170

Spermiogenesis converts haploid spermatids into spermatozoa, involving the acrosome's formation, nucleus condensation, flagellum development, and cytoplasm loss. The acrosome, derived from the Golgi complex, contains enzymes that dissociate corona radiata cells and digest the zona pellucida of the secondary oocyte. The flagellum's movement is powered by microtubules, ATP, and dynein.

Question 171

What are Sertoli cells?

Answer 171

Sertoli cells are columnar epithelial cells, predominant in the seminiferous tubules before puberty and in elderly men, but they make up only 10% of the cells during maximal spermatogenesis.

Question 172

What is the main function of Sertoli cells?

Answer 172

Sertoli cells support, protect, and provide nutrition to developing spermatozoa by shedding excess spermatid cytoplasm as residual bodies, which are then phagocytized, along with germ cells that fail to mature.

Question 173

How is the blood-testis barrier formed?

Answer 173

The blood-testis barrier is formed by a network of Sertoli cells that create tight junctions, dividing the seminiferous tubule into a basal compartment (containing spermatogonia and early primary spermatocytes) and an adlumenal compartment (containing more advanced spermatocytes and spermatids).

Question 174

What hormones do Sertoli cells produce?

Answer 174

Sertoli cells secrete androgen-binding protein (which binds testosterone and dihydrotestosterone), inhibin (which suppresses FSH synthesis), and anti-Müllerian hormone (during fetal life, to suppress the development of female reproductive structures).

Question 175

What happens to primary spermatocytes in relation to the blood-testis barrier?

Answer 175

Primary spermatocytes cross the blood-testis barrier through a mechanism that is not yet understood, even though the barrier formed by tight junctions between Sertoli cells protects the more advanced stages of spermatogenesis from blood-borne substances.

Question 176

What is the composition of the interstitial tissue in the testis?

Answer 176

The interstitial tissue between the seminiferous tubules consists of fibroblasts, collagen, blood and lymphatic vessels, and Leydig cells.

Question 177

What is the function of Leydig cells?

Answer 177

Leydig cells, also known as interstitial cells, synthesize testosterone.

Question 178

What happens after spermatozoa are produced in the seminiferous tubules?

Answer 178

Spermatozoa pass from the seminiferous tubules to the rete testis, then into 10–20 ductuli efferentes.

Question 179

What is the role of the ductuli efferentes in sperm transport?

Answer 179

The ductuli efferentes are lined with a single layer of epithelial cells, some of which are ciliated. The ciliary action helps propel the non-motile spermatozoa, while non-ciliated cells reabsorb fluid produced by the testis.

Question 180

What is the primary function of the epididymis?

Answer 180

The epididymis accumulates, stores, and matures spermatozoa. It is where spermatozoa become motile.

Question 181

What type of epithelium lines the epididymis, and what is its role?

Answer 181

The epididymis is lined with pseudostratified columnar epithelium containing stereocilia. This epithelium resorbs testicular fluid, phagocytizes residual bodies and poorly formed spermatozoa, and secretes substances that aid in sperm maturation.

Question 182

What is the function of the ductus deferens?

Answer 182

The ductus deferens conducts spermatozoa from the epididymis to the ejaculatory duct, and then into the prostatic urethra.

Question 183

What happens during a vasectomy?

Answer 183

A vasectomy involves the bilateral ligation of the vas deferens, preventing spermatozoa from moving from the epididymis to the urethra.

Question 184

Where are the seminal vesicles located and what is their structure?

Answer 184

The seminal vesicles are a pair of glands located on the posterior and inferior surfaces of the bladder. They have a highly convoluted structure with a folded mucosa lined with pseudostratified columnar epithelium.

Question 185

What is the role of the seminal vesicles in semen production?

Answer 185

The seminal vesicles produce a secretion that constitutes approximately 70% of human ejaculate, which is rich in substances that activate spermatozoa, including fructose, citrate, prostaglandins, and proteins. Fructose provides energy for sperm motility.

Question 186

How do the seminal vesicles connect to the urethra?

Answer 186

The duct of each seminal vesicle joins the ductus deferens to form an ejaculatory duct, which traverses the prostate and empties into the prostatic urethra.

Question 187

What is the structure of the prostate gland?

Answer 187

The prostate consists of 30–50 branched tubuloalveolar glands, whose ducts empty into the urethra. It is surrounded by a fibroelastic capsule rich in smooth muscle.

Question 188

What types of glands are found in the prostate, and where are they located?

Answer 188

There are periurethral submucosal glands and main prostatic glands in the periphery of the prostate.

Question 189

What is the nature of the glandular epithelium in the prostate?

Answer 189

The glandular epithelium in the prostate is pseudostratified columnar with pale, foamy cytoplasm and numerous secretory granules.

Question 190

What substances are produced by the prostate gland’s secretory granules?

Answer 190

The secretory granules of the prostate produce acid phosphatase, citric acid, fibrinolysin, and other proteins.

Question 191

What triggers penile erection?

Answer 191

Penile erection occurs in response to parasympathetic stimulation via the pelvic splanchnic nerves. Nitric oxide is released, causing relaxation of the corpus cavernosum and corpus spongiosum, allowing blood to accumulate in the erectile tissue.

Question 192

How does ejaculation occur?

Answer 192

Ejaculation is mediated by sympathetic nervous system stimulation via the lumbar splanchnic nerves, which moves mature spermatozoa from the epididymis and vas deferens into the ejaculatory duct.

Question 193

What is the role of accessory glands in ejaculation?

Answer 193

Accessory glands such as the bulbourethral (Cowper) glands, prostate, and seminal vesicles secrete fluids that help sperm survival and fertility.

Question 194

How does the somatic motor system contribute to ejaculation?

Answer 194

Somatic motor efferents (pudendal nerve) innervate the bulbospongiosus and ischiocavernous muscles at the base of the penis, stimulating the rapid ejection of semen out of the urethra during ejaculation.

Question 195

What role does the vas deferens play in ejaculation?

Answer 195

Peristaltic waves in the vas deferens aid in the more complete ejection of semen through the urethra during ejaculation.

Question 196

What can injury to the bulb of the penis result in?

Answer 196

Injury to the bulb of the penis may cause the extravasation of urine from the urethra into the superficial perineal space. Urine can then pass into the scrotum, penis, and onto the anterior abdominal wall.

Question 197

What does the accumulation of fluid in the scrotum, penis, and anterior abdominal wall indicate?

Answer 197

The accumulation of fluid in these areas suggests a laceration of either the membranous or penile urethra (deep to Scarpa fascia). This can occur due to trauma in the perineal region (saddle injury) or during urethral catheterization.

Question 198

What is histology?

Answer 198

Histology is the study of normal tissues. Groups of cells form tissues, which make up organs, organ systems, and ultimately the organism.

Question 199

What are the four types of tissue in organs?

Answer 199

The four types of tissue in organs are epithelial, connective, nervous, and muscular tissue.

Question 200

What defines epithelial cell polarity?

Answer 200

Epithelial cells are polarized, meaning their apical and basolateral surfaces have different structures, compositions, and functions. This polarity is established by tight junctions.

Question 201

What is the role of tight junctions in epithelial cells?

Answer 201

Tight junctions separate the apical and basolateral surfaces and regulate the paracellular pathway, preventing backflow and ensuring proper transport functions.

Question 202

What are the two basic mechanisms for epithelial transport?

Answer 202

The two basic mechanisms are: - Transcellular pathway (through the cell, used for larger molecules and ions). - Paracellular pathway (between cells).

Question 203

How do tight junctions contribute to epithelial function?

Answer 203

Tight junctions regulate the paracellular pathway by preventing the backflow of transported materials and maintaining separation of the basolateral and apical membrane components.

Question 204

What happens when epithelial polarity is disrupted?

Answer 204

When epithelial polarity is disrupted, diseases like cystic fibrosis can develop. In cystic fibrosis, the failure of apical chloride channels to open leads to thickened mucus due to the lack of water transport.

Question 205

What role do epithelial cells play in relation to connective tissue?

Answer 205

Epithelial cells are always supported by connective tissue on their basal side, which contains blood vessels. Since epithelia are avascular, interstitial tissue fluids supply them with oxygen and nutrients.

Question 206

What is the importance of epithelial renewal?

Answer 206

Epithelia renew themselves continuously, with some types like skin and intestinal linings renewing rapidly. This renewal process is supported by stem cells that proliferate continuously.

Question 207

Name an example of simple cuboidal epithelium.

Answer 207

Simple cuboidal epithelium can be found in renal tubules and salivary gland acini.

Question 208

What is an example of simple columnar epithelium?

Answer 208

An example of simple columnar epithelium is found in the small intestine.

Question 209

Where is simple squamous epithelium found?

Answer 209

Simple squamous epithelium is found in the endothelium, mesothelium, and the epithelial lining of the renal glomerular capsule.

Question 210

What are the types of stratified squamous epithelium?

Answer 210

Stratified squamous epithelium includes nonkeratinized (e.g., esophagus) and keratinized (e.g., skin) varieties.

Question 211

Where can pseudostratified columnar epithelium be found?

Answer 211

Pseudostratified columnar epithelium is found in the trachea and epididymis.

Question 212

What is transitional epithelium, and where is it found?

Answer 212

Transitional epithelium, or urothelium, is found in the ureter and bladder.

Question 213

What is an example of stratified cuboidal epithelium?

Answer 213

Stratified cuboidal epithelium is found in the ducts of salivary glands.

Question 214

What is the most common staining method for viewing tissues under a light microscope?

Answer 214

The most common staining method is hematoxylin-and-eosin (H&E) staining.

Question 215

What is the function of hematoxylin in H&E staining?

Answer 215

Hematoxylin is a blue dye that stains basophilic substrates, such as acidic cellular components like DNA and RNA. It stains the nuclei blue and may tint the cytoplasm of cells with abundant mRNA.

Question 216

What does eosin stain in H&E staining?

Answer 216

Eosin is a pink-to-orange dye that stains acidophilic substrates, such as basic components of proteins. It stains the cytoplasm of most cells and extracellular proteins like collagen pink.

Question 217

What components does hematoxylin specifically stain?

Answer 217

Hematoxylin specifically stains acidic cellular components, including DNA and RNA.

Question 218

Where is simple columnar epithelium found?

Answer 218

Simple columnar epithelium is found in the small and large intestine.

Question 219

What does simple squamous epithelium form?

Answer 219

Simple squamous epithelium forms the endothelium that lines blood vessels, the mesothelium in serous membranes, and the epithelium lining the inside of the renal glomerular capsule.

Question 220

Where is pseudostratified columnar epithelium found?

Answer 220

Pseudostratified columnar epithelium is found in the nasal cavity, trachea, bronchi, and epididymis.

Question 221

Where is transitional epithelium located?

Answer 221

Transitional epithelium is found in the ureter and bladder.

Question 222

Where is stratified squamous epithelium found?

Answer 222

Stratified squamous epithelium is found in the oral cavity, pharynx, and esophagus (non-keratinized) and in the skin (keratinizing).

Question 223

What is the function of simple cuboidal epithelium?

Answer 223

Simple cuboidal epithelium is found in the renal tubules and the secretory cells of salivary gland acini.

Question 224

Where is stratified cuboidal epithelium found?

Answer 224

Stratified cuboidal epithelium is found in the ducts of salivary glands.

Question 225

What are unicellular glands?

Answer 225

Unicellular glands are goblet cells found in the respiratory and gastrointestinal (GI) epithelium.

Question 226

What types of multicellular glands exist?

Answer 226

Multicellular glands may be exocrine (e.g., salivary gland) or endocrine (e.g., thyroid gland).

Question 227

What type of epithelium forms the tubules or acini of glands?

Answer 227

Tubules or acini in glands are mainly formed by simple cuboidal epithelium.

Question 228

Do exocrine glands have ducts?

Answer 228

Yes, exocrine glands have ducts that serve as conduits for glandular secretions to a body surface or lumen.

Question 229

What is the main difference between exocrine and endocrine glands?

Answer 229

Exocrine glands have ducts to transport secretions, whereas endocrine glands do not have ducts and release hormones directly into the bloodstream.

Question 230

What are microfilaments composed of?

Answer 230

Microfilaments are composed of actin proteins, which are made of globular monomers of G-actin that polymerize to form helical filaments of F-actin.

Question 231

What is the diameter of F-actin filaments?

Answer 231

F-actin filaments have a diameter of 7 nm.

Question 232

What is treadmilling in the context of actin filaments?

Answer 232

Treadmilling refers to the balance in the activity at the two ends of F-actin filaments, where polymerization occurs at the barbed end (plus end) and depolymerization occurs at the pointed end.

Question 233

What role do actin microfilaments play in cells?

Answer 233

Actin microfilaments, in conjunction with myosin, provide contractile and motile forces in cells, including the formation of the contractile ring during cytokinesis in mitosis and meiosis.

Question 234

Where are actin filaments found in relation to cell membranes?

Answer 234

Actin filaments are linked to cell membranes at tight junctions and zonula adherens, and they form the core of microvilli.

Question 235

What is the diameter of intermediate filaments?

Answer 235

Intermediate filaments have a diameter of 10 nm.

Question 236

What is the function of intermediate filaments?

Answer 236

Intermediate filaments provide structural stability to cells.

Question 237

What are the four types of intermediate filaments?

Answer 237

The four types of intermediate filaments are: - Type I: Keratins (found in epithelial cells) - Type II: Desmin, vimentin, glial fibrillary acidic protein, and peripherin (found in muscle cells, fibroblasts, endothelial cells, etc.) - Type III: Neurofilaments (found in neurons) - Type IV: Lamins (form a meshwork in the nuclear envelope of all cells)

Question 238

What is the diameter of microtubules?

Answer 238

Microtubules have a diameter of 25 nm.

Question 239

What is the function of microtubules in cells?

Answer 239

Microtubules provide tracks for intracellular transport of vesicles and molecules and are particularly important in axons.

Question 240

What are the motor molecules involved in microtubule transport?

Answer 240

Dynein drives retrograde transport, while kinesin drives anterograde transport.

Question 241

Where are microtubules found?

Answer 241

Microtubules are found in true cilia and flagella, where they utilize dynein for motility, and also form the mitotic spindle during mitosis and meiosis.

Question 242

What happens when cadherins are lost in malignant cells?

Answer 242

A loss of cadherin expression weakens the epithelium, facilitating the first step in the invasion of malignant cells through the epithelium.

Question 243

How do intermediate filament changes manifest in Alzheimer’s disease and cirrhotic liver diseases?

Answer 243

Changes in intermediate filaments are evident in neurons in Alzheimer’s disease and in the liver in cirrhotic conditions.

Question 244

What is the role of colchicine in gout?

Answer 244

Colchicine prevents microtubule polymerization and is used to prevent neutrophil migration in gout.

Question 245

How are vinblastine and vincristine used in cancer therapy?

Answer 245

Vinblastine and vincristine inhibit the formation of the mitotic spindle, making them effective in cancer therapy.

Question 246

What is the primary rotation of the midgut during development?

Answer 246

The midgut undergoes a 270° counterclockwise rotation around the axis of the superior mesenteric artery during weeks 6–10​

Question 247

What results from the midgut's rotation?

Answer 247

The rotation places the jejunum on the left, the ileum and cecum on the right, and shapes the colon into an inverted "U"​

Question 248

What layers compose the peritoneum?

Answer 248

The peritoneum consists of two layers: parietal peritoneum (lining the body wall) and visceral peritoneum (enclosing intraperitoneal organs)​

Question 249

What is the function of mesenteries formed by the visceral peritoneum?

Answer 249

Mesenteries suspend parts of the GI tract from the body wall, allowing the passage of vessels, nerves, and lymphatics​

Question 250

What is the significance of the epiploic foramen (of Winslow)?

Answer 250

It connects the lesser sac (omental bursa) and the greater sac of the peritoneal cavity.

Question 251

What is the origin of the hepatic diverticulum, and what does it form?

Answer 251

The hepatic diverticulum originates as an endodermal outgrowth of the foregut near the duodenum and forms the liver, gallbladder, and biliary duct system​

Question 252

What are the components of the ventral embryonic mesentery in liver development?

Answer 252

The part between the liver and the gut tube becomes the lesser omentum, and the part between the liver and the ventral body wall becomes the falciform ligament​

Question 253

How does the pancreas develop?

Answer 253

The pancreas develops from two endodermal buds (ventral and dorsal) of the foregut near the duodenum. The ventral bud rotates and fuses with the dorsal bud, forming the pancreas​

Question 254

What structures arise from the dorsal pancreatic bud?

Answer 254

The dorsal pancreatic bud forms the neck, body, and tail of the pancreas​

Question 255

What does the ventral pancreatic bud form?

Answer 255

The ventral pancreatic bud forms the head and uncinate process of the pancreas​

Question 256

What structures does the primitive gut tube form during body folding?

Answer 256

The primitive gut tube forms through head-to-tail (cranial-caudal) and lateral body foldings, incorporating the yolk sac into the embryo. The epithelial lining is derived from endoderm, while the lamina propria, muscularis mucosae, submucosa, muscularis externa, and adventitia/serosa arise from mesoderm​

Question 257

How is the primitive gut tube divided, and what supplies each region?

Answer 257

The primitive gut tube is divided into the foregut, midgut, and hindgut, each supplied by specific arteries and autonomic nerves​

Question 258

What is the difference between direct and indirect inguinal hernias?

Answer 258

- Direct inguinal hernias occur medial to the inferior epigastric vessels, passing through the inguinal triangle (Hesselbach's triangle). - Indirect inguinal hernias occur lateral to the inferior epigastric vessels, entering through the deep inguinal ring​.

Question 259

What are femoral hernias, and where do they occur?

Answer 259

Femoral hernias pass below the inguinal ligament and most commonly occur in women. They herniate through the femoral canal​

Question 260

What clinical significance does the epiploic foramen (of Winslow) have?

Answer 260

The epiploic foramen connects the omental bursa (lesser sac) to the greater peritoneal sac. It is bounded anteriorly by the hepatoduodenal ligament and hepatic portal vein, posteriorly by the inferior vena cava, superiorly by the caudate lobe of the liver, and inferiorly by the first part of the duodenum​

Question 261

What is the blood supply to the spleen, and where is it located?

Answer 261

The splenic artery and vein reach the spleen's hilum by traversing the splenorenal ligament. The spleen is a peritoneal organ in the upper left quadrant, deep to the left 9th–11th ribs​

Question 262

What are the anatomical regions of the stomach?

Answer 262

- Cardiac region: Receives the esophagus. - Fundus: Dome-shaped upper portion, often filled with air. - Body: Central part. - Pyloric portion: Thick muscular wall with a narrow lumen that empties into the duodenum​.

Question 263

What are the functions of the duodenum, and how is it structured?

Answer 263

The duodenum is C-shaped, has four parts, and is retroperitoneal except for the first part. It mixes chyme with pancreatic enzymes and bile while continuing digestion​

Question 264

What is the clinical relevance of a sliding hiatal hernia?

Answer 264

A sliding hiatal hernia occurs when the stomach's cardia herniates through the esophageal hiatus of the diaphragm, potentially damaging the vagal trunks​

Question 265

What is the role of Peyer's patches in the ileum?

Answer 265

Peyer's patches are clusters of lymphoid tissue in the ileum's mucosa that detect antigens and facilitate immune responses​

Question 266

What is the rotation of the abdominal foregut during development?

Answer 266

The abdominal foregut rotates 90° clockwise around its longitudinal axis, turning the original left side of the stomach into the ventral surface, and forming the lesser and greater curvatures​

Question 267

How does foregut rotation affect the positioning of abdominal structures?

Answer 267

The liver, lesser omentum, pylorus, and duodenum move to the right, while the spleen, pancreas, and greater omentum move to the left​

Question 268

What embryonic mesenteries contribute to abdominal ligaments?

Answer 268

- Ventral embryonic mesentery forms the lesser omentum and falciform ligament. - Dorsal embryonic mesentery forms the greater omentum, gastro-splenic ligament, and splenorenal ligament​.

Question 269

What structures develop from the endodermal outgrowth of the foregut?

Answer 269

The lower respiratory tract, liver and biliary system, and pancreas​

Question 270

What happens during the development and rotation of the midgut?

Answer 270

The midgut herniates into the umbilical cord during weeks 6–10, undergoing a 270° counterclockwise rotation around the axis of the superior mesenteric artery. This positions the jejunum on the left and the ileum and cecum on the right, shaping the colon into an inverted "U"​

Question 271

What are the two layers of the peritoneum?

Answer 271

The peritoneum consists of the parietal layer, which lines the abdominal wall, and the visceral layer, which covers the abdominal organs​

Question 272

What is the function of mesenteries in the peritoneum?

Answer 272

Mesenteries suspend parts of the gastrointestinal tract from the body wall and allow the passage of blood vessels, lymphatics, and nerves​

Question 273

What is the epiploic foramen (of Winslow), and what is its clinical importance?

Answer 273

The epiploic foramen connects the lesser sac (omental bursa) to the greater sac of the peritoneal cavity. It is an important landmark in surgeries involving the hepatoduodenal ligament​

Question 274

What is the rotation of the foregut during development?

Answer 274

The foregut rotates 90° clockwise around its longitudinal axis, positioning the liver, lesser omentum, pylorus, and duodenum to the right, and the spleen, pancreas, and greater omentum to the left​

Question 275

Which structures form from the ventral and dorsal embryonic mesenteries?

Answer 275

- Ventral mesentery: Forms the lesser omentum and falciform ligament. - Dorsal mesentery: Forms the greater omentum, gastro-splenic ligament, and splenorenal ligament​.

Question 276

What are the anatomical features of the large intestine?

Answer 276

The large intestine includes the cecum, appendix, colon, rectum, and anal canal. Its surface lacks villi, has short crypts of Lieberkühn, and contains lymphoid follicles, especially in the cecum and appendix​

Question 277

What is the primary function of the colon?

Answer 277

The colon reabsorbs fluids and electrolytes while temporarily storing feces. Some digestion occurs through bacterial flora, breaking down cellulose​

Question 278

What is the role of Paneth cells in the small intestine?

Answer 278

Paneth cells, located at the base of crypts, protect against microorganisms by secreting lysozyme and defensins​

Question 279

What forms the ventral embryonic mesentery in liver development?

Answer 279

The ventral embryonic mesentery forms the lesser omentum and the falciform ligament.

Question 280

How does the pancreas develop?

Answer 280

The pancreas develops from two endodermal buds (ventral and dorsal) of the foregut. The ventral bud rotates and fuses with the dorsal bud to form a single pancreas.

Question 281

What structures are formed by the dorsal and ventral pancreatic buds?

Answer 281

- The dorsal pancreatic bud forms the neck, body, and tail of the pancreas. - The ventral pancreatic bud forms the head and uncinate process.

Question 282

What is annular pancreas, and what is its clinical significance?

Answer 282

Annular pancreas occurs when the ventral and dorsal pancreatic buds form a ring around the duodenum, causing obstruction, often associated with polyhydramnios.

Question 283

What are the consequences of hypertrophic pyloric stenosis?

Answer 283

Hypertrophic pyloric stenosis involves muscular hypertrophy of the pylorus, leading to projectile, nonbilious vomiting and a palpable knot near the right costal margin.

Question 284

What structures form from the hepatic diverticulum?

Answer 284

The hepatic diverticulum forms the liver, gallbladder, and the biliary duct system.

Question 285

Embryology of Bladder and Urethra

Answer 285

The hindgut remains stationary and does not undergo rotation during development. By week 7, the urorectal septum forms and divides the cloaca into the anorectal canal, which is the precursor to the rectum and anus, and the urogenital sinus, which is the precursor to the bladder and parts of the urethra.

Question 286

What is the origin of the urinary bladder in embryology?

Answer 286

Answer: The upper part of the urogenital sinus (endoderm) becomes the urinary bladder, which is initially continuous with the allantois.

Question 287

Question: What happens to the allantois during the development of the bladder?

Answer 287

Answer: The lumen of the allantois becomes obliterated to form the urachus, which connects the apex of the bladder to the umbilicus. In adults, this structure becomes the median umbilical ligament.

Question 288

Question: How is the trigone of the bladder formed?

Answer 288

Answer: The trigone of the bladder is formed by the incorporation of the caudal mesonephric ducts into the dorsal bladder wall, and it becomes covered by endodermal epithelium.

Question 289

Question: From which tissue is the smooth muscle of the bladder derived?

Answer 289

Answer: The smooth muscle of the bladder is derived from splanchnic mesoderm.

Question 290

Question: What do the mesonephric ducts form during the development of the bladder?

Answer 290

Answer: The mesonephric ducts form the ejaculatory ducts as they enter the prostatic urethra.

Question 291

Question: What part of the urogenital sinus forms the urethra in females?

Answer 291

Answer: The middle part of the urogenital sinus (endoderm) forms the entire urethra in females.

Question 292

Question: What does the middle part of the urogenital sinus form in males?

Answer 292

Answer: In males, the middle part of the urogenital sinus forms the prostatic, membranous, and proximal spongy urethra.

Question 293

Question: What is the origin of the prostate gland in males?

Answer 293

Answer: The prostate gland is formed by an endodermal outgrowth of the prostatic urethra.

Question 294

Question: What does the inferior part of the urogenital sinus form?

Answer 294

Answer: The inferior part of the urogenital sinus forms the lower vagina and contributes to the primordia of the penis or the clitoris.

Question 295

Question: Where does the anorectal canal form?

Answer 295

Answer: The anorectal canal forms the hindgut distally to the pectinate line.

Question 296

What is renal agenesis and its association with Potter sequence?

Answer 296

Renal agenesis results from the failure of one or both kidneys to develop due to early degeneration of the ureteric bud. Unilateral agenesis is common, while bilateral agenesis is fatal and is associated with oligohydramnios. The fetus may also have Potter sequence, which includes clubbed feet, pulmonary hypoplasia, and craniofacial anomalies.

Question 297

What is a pelvic kidney?

Answer 297

Pelvic kidney is caused by a failure of one kidney to ascend during development.

Question 298

What is a horseshoe kidney?

Answer 298

Horseshoe kidney is a fusion of both kidneys at their ends, with failure of the fused kidney to ascend. It is usually associated with normal renal function but a predisposition to calculi. The horseshoe kidney hooks under the origin of the inferior mesenteric artery.

Question 299

What causes a double ureter?

Answer 299

A double ureter is caused by the early splitting of the ureteric bud or the development of two separate buds.

Question 300

What happens when the allantois fails to be obliterated?

Answer 300

Failure of the allantois to be obliterated results in urachal fistulas or sinuses. In male children with congenital valvular obstruction of the prostatic urethra or in older men with enlarged prostates, a patent urachus may cause drainage of urine through the umbilicus.

Question 301

What is the size and location of the kidneys?

Answer 301

The kidneys are a pair of bean-shaped organs approximately 12 cm long. They extend from vertebral level T12 to L3 when the body is in the erect position. The right kidney is positioned slightly lower than the left due to the mass of the liver.

Question 302

What structures are in contact with the kidneys?

Answer 302

Both kidneys are in contact with the diaphragm, psoas major, and quadratus lumborum.

Question 303

Where does the right kidney contact the body?

Answer 303

The right kidney contacts the diaphragm, psoas major, quadratus lumborum, and the 12th rib.

Question 304

Where does the left kidney contact the body?

Answer 304

The left kidney contacts the diaphragm, psoas major, quadratus lumborum, and the 11th and 12th ribs.

Question 305

What are the ureters and where do they connect?

Answer 305

The ureters are fibromuscular tubes that connect the kidneys to the urinary bladder in the pelvis.

Question 306

Where do the ureters run in the body?

Answer 306

The ureters run posterior to the ductus deferens in males and posterior to the uterine artery in females. They begin as continuations of the renal pelves and run retroperitoneally, crossing the external iliac arteries as they pass over the pelvic brim. The ureter lies on the anterior surface of the psoas major muscle.

Question 307

What are the most common sites of ureteral constriction susceptible to blockage by renal calculi?

Answer 307

The most common sites are: * Where the renal pelvis joins the ureter * Where the ureter crosses the pelvic inlet * Where the ureter enters the wall of the urinary bladder

Question 308

What is the structure and blood supply of the urinary bladder?

Answer 308

The urinary bladder is covered superiorly by peritoneum. The body is a hollow muscular cavity. * The neck is continuous with the urethra. * The trigone is a smooth, triangular area of mucosa located at the base of the bladder. * The base of the triangle is superior and bounded by the 2 openings of the ureters. The apex of the trigone points inferiorly and is the opening for the urethra. * Blood supply: Vesicular branches of the internal iliac arteries and umbilical arteries. * Venous drainage: Vesicular venous plexus drains to internal iliac veins.

Question 309

What is the lymphatic drainage and innervation of the urinary bladder?

Answer 309

* Lymphatics: Drain to the external and internal iliac nodes. * Innervation: – Parasympathetic: S2, S3, S4 (pelvic splanchnic nerves to the detrusor muscle). – Sympathetic: L1-L2 (lumbar splanchnics to the trigone muscle and internal urethral sphincter).

Question 310

What muscles are involved in urinary bladder function?

Answer 310

* The detrusor muscle: Forms most of the bladder wall and contracts during micturition. Controlled by parasympathetic fibers (S2, S3, S4). * The internal urethral sphincter: Smooth muscle fibers at the neck of the bladder. Controlled by sympathetic fibers (T11-L2) during bladder filling to prevent leakage. * The external urethral sphincter: Voluntary skeletal muscle that surrounds the urethra. Innervated by the pudendal nerve and relaxed during micturition.

Question 311

What is the structure of the male urethra?

Answer 311

The male urethra is approximately 20 cm in length, extending from: * The neck of the bladder through the prostate gland (prostatic urethra). * Through the urogenital diaphragm (membranous urethra). * To the external opening at the glans (penile or spongy urethra).

Question 312

What is the role of parasympathetic and sympathetic fibers in micturition?

Answer 312

Parasympathetic fibers facilitate micturition, while sympathetic fibers inhibit micturition.

Question 313

What is spastic bladder and what causes it?

Answer 313

Spastic bladder results from lesions of the spinal cord above the sacral spinal cord levels. It causes a loss of inhibition of the parasympathetic nerve fibers that innervate the detrusor muscle during the filling stage, leading to urge incontinence as the detrusor muscle responds to minimal stretch.

Question 314

What is atonic bladder and what causes it?

Answer 314

Atonic bladder results from lesions to the sacral spinal cord segments or the sacral spinal nerve roots. Loss of pelvic splanchnic motor innervation leads to loss of contraction of the detrusor muscle, resulting in a full bladder with a continuous dribble of urine.

Question 315

What can weakness of the puborectalis part of the levator ani muscle or the sphincter urethrae part of the urogenital diaphragm lead to?

Answer 315

Weakness of the puborectalis part of the levator ani muscle may result in rectal incontinence. Weakness of the sphincter urethrae part of the urogenital diaphragm may result in urinary incontinence.

Question 316

What are the divisions of the male urethra, and how is the distal spongy urethra derived?

Answer 316

The male urethra is anatomically divided into 3 portions: prostatic, membranous, and spongy (penile). The distal spongy urethra of the male is derived from the ectodermal cells of the glans penis.

Question 317

What is the length of the female urethra, and where does it extend from and to?

Answer 317

The female urethra is approximately 4 cm in length and extends from the neck of the bladder to the external urethral orifice of the vulva.

Question 318

What structures make up the urinary system?

Answer 318

The urinary system consists of 2 kidneys, 2 ureters, the bladder, and the urethra.

Question 319

What are the functions of the urinary system?

Answer 319

The urinary system removes waste products from the blood, regulates fluid balance, salt balance, and acid-base balance. The kidneys also produce and release renin, erythropoietin, and prostaglandins.

Question 320

What is the structure of the kidney?

Answer 320

A sagittal section through the kidney shows a capsule surrounding the organ, a cortex with radial striations and glomeruli, and a medulla with an outer and inner zone. The papilla borders a space surrounded by calices of the ureter.

Question 321

What is the structure of the kidney's cortex?

Answer 321

The cortex is divided into lobules containing nephron elements, vascular elements, and stroma. At the center of each lobule is a medullary ray, with tubules oriented radially. The edges of each lobule contain glomeruli and large arterioles and venules.

Question 322

What is the structure of the kidney's medulla?

Answer 322

The medulla contains radially arranged straight tubules running from the cortex to the papilla, vascular elements, and stroma. The medulla is divided into two zones: the outer medulla with varied tubule profiles and the inner medulla with fewer, similar tubes.

Question 323

How does blood circulation work in the kidney?

Answer 323

The renal artery branches into interlobar arteries, then into arcuate arteries, and finally into interlobular arterioles. Each intralobular arteriole feeds a glomerulus, where it forms a tuft of capillaries. The efferent arteriole exits the corpuscle and forms a second capillary bed, which connects to venules.

Question 324

How much cardiac output does the kidney receive?

Answer 324

The kidneys receive 25% of the total cardiac output, which is approximately 1,700 liters of blood per day.

Question 325

What is unique about the kidney's arteriole-capillary system?

Answer 325

The kidney has a unique arteriole-capillary-arteriole-capillary-vein sequence. The afferent arteriole leads into a glomerulus, and the efferent arteriole exits the glomerulus and forms a second capillary bed in the cortex.

Question 326

What is the functional unit of the kidney?

Answer 326

The functional unit of the kidney is the nephron. Each kidney contains 1–1.3 million nephrons.

Question 327

How do nephrons and collecting ducts work together?

Answer 327

Nephrons connect to collecting ducts, which receive urine from multiple nephrons. The collecting ducts converge and eventually open, allowing urine to flow out of the kidney.

Question 328

What is the length of a nephron and its components?

Answer 328

A nephron is about 55 mm in length and begins with Bowman’s capsule, which is the enlarged end of the nephron.

Question 329

What are the layers of Bowman’s capsule?

Answer 329

Bowman’s capsule has two layers: the visceral layer in direct contact with the capillary endothelium and the parietal layer surrounding the urinary space.

Question 330

What forms the renal corpuscle?

Answer 330

The renal corpuscle is formed by Bowman’s capsule and the glomerulus of capillaries.

Question 331

What is the parietal layer of Bowman’s capsule continuous with?

Answer 331

The parietal layer of Bowman’s capsule is continuous with the walls of the proximal convoluted tubule (PCT).

Question 332

What are podocytes and what is their shape?

Answer 332

Podocytes are visceral layer cells of Bowman’s capsule with a complex shape. Their cell body has extensive primary and secondary foot processes.

Question 333

How do podocytes interact with blood vessels in the renal corpuscle?

Answer 333

The foot processes of the podocytes surround the blood vessels and lie on a basal lamina shared by capillary endothelial cells.

Question 334

What do the podocyte foot processes cover?

Answer 334

The podocyte foot processes almost completely cover the capillary surfaces, leaving small slits in between.

Question 335

What structures make up the filtration barrier in the renal corpuscle?

Answer 335

The filtration barrier is formed by the combined capillary endothelium-podocyte complex.

Question 336

What are fenestrations in the capillary endothelium and what do they allow?

Answer 336

Fenestrations are large (50–100 nm) openings in the capillary endothelium that allow free flow of plasma but block the exit of cells.

Question 337

What is the function of the shared basal lamina of podocytes and endothelium?

Answer 337

The shared basal lamina acts as the first, coarser filtration barrier, blocking the passage of molecules larger than 70 kD.

Question 338

What are the thin diaphragms covering the slit openings between podocyte foot processes?

Answer 338

The thin diaphragms act as a more selective filter, composed of elongated proteins that form a zipper-like configuration over the slits.

Question 339

What is the width of the junction between adjacent podocytes, and what factors influence it?

Answer 339

The junction varies between 20 and 50 nm and may be influenced by perfusion pressures of the glomerulus.

Question 340

Are podocyte foot processes motile, and what do they contain?

Answer 340

Yes, podocyte foot processes are motile and contain actin and myosin.

Question 341

What connects the podocyte foot processes to each other and to the basal lamina?

Answer 341

The slit diaphragm and the actin cytoskeleton connect the foot processes to each other and to the basal lamina.

Question 342

How do alterations in the slit diaphragm molecular complex affect health?

Answer 342

Alterations in the composition or arrangement of these complexes are associated with various human and experimental diseases.

Question 343

Where does the proximal convoluted tubule (PCT) open, and what is its structure?

Answer 343

The PCT opens at the urinary pole of Bowman’s capsule. It has tall cells with pink cytoplasm, long apical microvilli, and extensive basal invaginations.

Question 344

What is the function of the basal invaginations in PCT cells?

Answer 344

The basal invaginations of PCT cells are involved in active transport, and numerous large mitochondria are located between them to provide energy for this process.

Question 345

What characterizes the lumen of the proximal convoluted tubule (PCT)?

Answer 345

The lumen of the PCT is often clouded by microvilli, which do not preserve well during histologic preparation.

Question 346

What are the key features of the loop of Henle?

Answer 346

The loop of Henle has a smaller diameter than the PCT and consists of descending and ascending limbs, which travel in opposite directions. Some loops have a wider segment before the distal tubule.

Question 347

How does the loop of Henle contribute to urine concentration?

Answer 347

The loop of Henle operates as a "countercurrent multiplier," creating a gradient of extracellular fluid tonicity in the medulla, which helps modulate urine tonicity and volume.

Question 348

Where does the distal convoluted tubule (DCT) make contact, and what is its function?

Answer 348

The DCT makes contact with its own glomerulus and then connects to the collecting tubule. It is involved in less active transport than the PCT and mainly handles passive water movements.

Question 349

What is the structure of the epithelium in the DCT, loops of Henle, and collecting ducts?

Answer 349

The epithelium of these structures varies in thickness and cell border definition, with limited surface microvilli in some regions.

Question 350

What are principal cells in the collecting ducts, and what is their role?

Answer 350

Principal cells in the collecting ducts respond to aldosterone, which regulates sodium and water balance.

Question 351

Where are mesangial cells located, and what is their function?

Answer 351

Mesangial cells are located between capillaries and the basal lamina, outside the capillary lumen. They are phagocytic and may help maintain the basal lamina.

Question 352

What diseases are associated with abnormalities of mesangial cells?

Answer 352

Abnormalities in mesangial cells can result in clogged and/or distorted glomeruli, affecting kidney function.

Question 353

Where is erythropoietin produced in the kidneys?

Answer 353

Erythropoietin is produced by renal cortex and medullary fibroblasts (interstitial cells).

Question 354

How do diuretics work?

Answer 354

Diuretics work by inhibiting sodium (Na+) resorption, which leads to an increase in sodium and water excretion.

Question 355

What is the juxtaglomerular complex and what is its function?

Answer 355

It is a group of cells that includes the juxtaglomerular apparatus (in the afferent arteriole), the macula densa (in the distal convoluted tubule), and mesangial cells. JG cells secrete renin, and the macula densa detects sodium levels in the tubular fluid.

Question 356

What are alveolar macrophages, and what is their role in the lungs?

Answer 356

Alveolar macrophages are derived from monocytes and can undergo limited mitosis. They reside in the interalveolar septa and alveoli, acting as the lungs' last defense mechanism. They patrol alveolar surfaces, can pass through the pores of Kohn, and vary in size (15–40 microns). They either enter the lymphatics or are trapped in the mucus layer, eventually being propelled toward the pharynx to be swallowed and digested.

Question 357

What are other names for alveolar macrophages and why are they called that?

Answer 357

Alveolar macrophages are also called "dust cells" because they have phagocytosed dust or cigarette particles, and "heart failure cells" because they have phagocytosed blood cells that escape into the alveolar space during congestive heart failure.

Question 358

Question: Where does the heart develop from in the embryo?

Answer 358

The heart develops from splanchnic mesoderm in the latter half of week 3, within the cardiogenic area at the cranial end of the embryo.

Question 359

What cells migrate into the developing heart and what role do they play?

Answer 359

Neural crest cells migrate into the developing heart and play an important role in cardiac development.

Question 360

How are the primordial heart tubes formed?

Answer 360

Cardiogenic cells condense to form a pair of primordial heart tubes, which will fuse into a single heart tube during body folding.

Question 361

What happens to the heart tube during body folding?

Answer 361

The heart tube undergoes dextral looping (bends to the right) and rotation.

Question 362

How do the different segments of the heart position themselves during development?

Answer 362

The upper truncus arteriosus (ventricular) end of the tube grows more rapidly and folds downward, ventrally, and to the right. The atria and sinus venosus (lower part) fold upward, dorsally, and to the left, placing the chambers of the heart in their postnatal anatomical positions.

Question 363

How many dilatations form in the primitive heart tube and what happens to them?

Answer 363

The primitive heart tube forms 4 dilatations and a cranial outflow tract, the truncus arteriosus. The fates of these dilatations are shown in the text.

Question 364

What are the three major venous systems that flow into the sinus venosus end of the heart tube during fetal circulation?

Answer 364

The three major venous systems are the vitelline veins, umbilical veins, and cardinal veins.

Question 365

What do the vitelline veins drain, and what do they contribute to in adult life?

Answer 365

The vitelline veins drain deoxygenated blood from the yolk stalk and later contribute to the veins of the liver, including the sinusoids, hepatic portal vein, hepatic vein, and part of the inferior vena cava.

Question 366

What does the umbilical vein carry, and where does it send oxygenated blood?

Answer 366

The umbilical vein carries oxygenated blood from the placenta.

Question 367

What do the cardinal veins carry, and what major veins do they form in adult life?

Answer 367

The cardinal veins carry deoxygenated blood from the embryo’s body and later contribute to the brachiocephalic, superior vena cava, inferior vena cava, azygos, and renal veins.

Question 368

How does the ductus venosus affect blood flow in fetal circulation?

Answer 368

The ductus venosus allows oxygenated blood in the umbilical vein to bypass the liver sinusoids and flow directly into the inferior vena cava and right atrium.

Question 369

What is the function of the foramen ovale during fetal circulation?

Answer 369

The foramen ovale allows oxygenated blood to bypass the pulmonary circulation and flow from the right atrium to the left atrium and left ventricle.

Question 370

What does the ductus arteriosus shunt during fetal circulation?

Answer 370

The ductus arteriosus shunts deoxygenated blood from the pulmonary trunk to the aorta, bypassing the lungs.

Question 371

Why does right-to-left shunting occur in fetal circulation?

Answer 371

Right-to-left shunting occurs because of a right-to-left pressure gradient during fetal life.

Question 372

How do the three shunts close after birth?

Answer 372

The three shunts close due to changes in pressure gradients and oxygen tensions. The closure involves changes in blood flow and smooth muscle contraction.

Question 373

How does lung expansion contribute to the closure of fetal shunts after birth?

Answer 373

Lung expansion reduces pulmonary resistance, increases flow to the lungs, and enhances venous return to the left atrium, helping to close the shunts.

Question 374

How does the closure of the foramen ovale occur?

Answer 374

The closure of the foramen ovale occurs due to an increase in left atrial pressure and a decrease in right atrial pressure.

Question 375

What causes the closure of the ductus venosus and ductus arteriosus after birth?

Answer 375

The closure of the ductus venosus and ductus arteriosus occurs due to smooth muscle contraction and increased oxygen tension.

Question 376

How does the release of bradykinin and the drop in prostaglandin E facilitate the closure of the ductus arteriosus?

Answer 376

The release of bradykinin and the drop in prostaglandin E at birth facilitate the closure of the ductus arteriosus by promoting smooth muscle contraction.

Question 377

Pressure Gradients

Answer 377

Fetal R → L Postnatal L → R

Question 378

What part of the embryonic heart tube develops into the right and left horns?

Answer 378

The sinus venosus of the embryonic heart tube develops into the right and left horns.

Question 379

When does the septation of the atria and ventricles begin and mostly finish?

Answer 379

The septation of the atria and ventricles begins in week 4 and is mostly finished by week 8.

Question 380

What is the cause of most common congenital cardiac anomalies?

Answer 380

Most common congenital cardiac anomalies result from defects in the formation of the septa.

Question 381

How is blood shunted from the right to the left atrium during fetal life?

Answer 381

Blood is shunted from the right to the left atrium via the foramen ovale (FO).

Question 382

Why is the right atrial pressure higher than left atrial pressure during fetal life?

Answer 382

The right atrial pressure is higher than left due to the large bolus of blood directed into the right atrium from the placenta and high pulmonary resistance.

Question 383

Why must the foramen ovale remain open during fetal life?

Answer 383

The foramen ovale must remain open and functional to shunt oxygenated blood from the right atrium into the left atrium during fetal life.

Question 384

What is the function of the foramen ovale (FO) during fetal life?

Answer 384

The foramen ovale allows oxygenated blood to be shunted from the right atrium into the left atrium.

Question 385

Why is the higher right atrial pressure important for the fetal circulation?

Answer 385

The higher right atrial pressure is important to direct the large bolus of blood from the placenta into the right atrium and to overcome high pulmonary resistance.

Question 386

What happens if the foramen ovale does not remain open during fetal life?

Answer 386

If the foramen ovale does not remain open, it will impede the shunting of oxygenated blood from the right atrium to the left atrium, which is critical for fetal circulation.

Question 387

What happens at the beginning of week 4 in atrial septation?

Answer 387

The common atrium is divided into the right and left atria by two septa and two foramina.

Question 388

How does the septum primum (SP) contribute to atrial septation?

Answer 388

The septum primum grows inferiorly from the roof of the common atrium towards the endocardial cushions, eventually fusing with them, but initially, it does not reach them.

Question 389

What is the foramen primum (FP), and what happens to it during septation?

Answer 389

The foramen primum is located between the inferior edge of the septum primum and the endocardial cushion. It is obliterated when the septum primum fuses with the endocardial cushions.

Question 390

How is the foramen secundum (FS) formed, and what is its purpose?

Answer 390

The foramen secundum forms in the upper part of the septum primum just before the foramen primum closes, maintaining the right-to-left shunting of oxygenated blood into the right atrium.

Question 391

What role does the septum secundum (SS) play in atrial septation?

Answer 391

The septum secundum forms to the right of the septum primum, descends, and partially covers the foramen secundum, but it does not fuse with the endocardial cushions.

Question 392

What is the foramen ovale (FO), and how does it form?

Answer 392

The foramen ovale is the opening between the septum primum and septum secundum.

Question 393

What causes the closure of the foramen ovale (FO) after birth?

Answer 393

The closure of the foramen ovale occurs due to increased left atrial pressure resulting from changes in pulmonary circulation, and decreased right atrial pressure due to the closure of the umbilical vein.

Question 394

What is an atrial septal defect (ASD), and how is it typically classified?

Answer 394

Atrial septal defect (ASD) is a congenital heart defect that is more common in female births. It results in left-to-right shunting and is a non-cyanotic condition. The two clinically important types of ASD are secundum and primum.

Question 395

What is the most common type of ASD, and how does it occur?

Answer 395

The secundum-type ASD is the most common and is caused by excessive resorption of the septum primum (SP) or underdevelopment of the septum secundum (SS), or both. This leads to variable openings between the right and left atria in the central part of the atrial septum.

Question 396

What are the clinical implications of a small secundum-type ASD?

Answer 396

If the ASD is small, clinical symptoms may be delayed until as late as age 30.

Question 397

What is a primum-type ASD, and how does it occur?

Answer 397

The primum-type ASD is less common than the secundum-type and results from a failure of the septum primum to fuse with the endocardial cushions. It may be associated with defects of the endocardial cushions.

Question 398

Where do primum-type ASDs typically occur, and what associated defects might they have?

Answer 398

Primum ASDs occur in the lower aspect of the atrial wall, usually with a normally formed fossa ovalis. If the endocardial cushion is involved, a primum ASD can also be associated with defects of the membranous interventricular septum and the atrioventricular valves.

Question 399

What type of conditions are right-to-left shunts associated with postnatally?

Answer 399

Right-to-left shunts are cyanotic conditions.

Question 400

What type of conditions are left-to-right shunts associated with postnatally?

Answer 400

Left-to-right shunts are non-cyanotic conditions.

Question 401

When does the development of the interventricular (IV) septum begin, and when is it usually completed?

Answer 401

The development of the interventricular septum begins in week 4 and is usually completed by the end of week 7.

Question 402

What are the two parts of the adult interventricular septum?

Answer 402

The adult interventricular septum consists of a large, muscular component forming most of the septum and a thin, membranous part forming a small component at the superior aspect of the septum.

Question 403

How does the muscular interventricular septum develop?

Answer 403

The muscular interventricular septum develops in the floor of the ventricle, ascends, and partially separates the right and left ventricles, leaving the interventricular foramen.

Question 404

What closes the interventricular foramen, and how does it form?

Answer 404

The membranous interventricular septum closes the interventricular foramen. It forms by the fusion of the right conotruncal ridge, the left conotruncal ridge, and the endocardial cushion, with neural crest cells associated with these structures.

Question 405

What is the most common congenital heart defect, and which gender is it more common in?

Answer 405

The most common congenital heart defect is ventricular septal defect (VSD), and it is more common in males than in females.

Question 406

What is the most common form of VSD, and what causes it?

Answer 406

The most common form of VSD is a membranous VSD, which is associated with the failure of neural crest cells to migrate into the endocardial cushions.

Question 407

What causes a membranous VSD?

Answer 407

A membranous VSD is caused by the failure of the membranous interventricular septum to develop, resulting in left-to-right shunting of blood through the interventricular foramen.

Question 408

What are the symptoms of patients with left-to-right shunting due to VSD?

Answer 408

Patients with left-to-right shunting complain of excessive fatigue upon exertion.

Question 409

How does left-to-right shunting of blood affect the lungs?

Answer 409

Left-to-right shunting is noncyanotic but causes increased blood flow and pressure to the lungs, leading to pulmonary hypertension.

Question 410

What changes occur in the pulmonary arteries due to pulmonary hypertension caused by left-to-right shunting?

Answer 410

Pulmonary hypertension causes marked proliferation of the tunica intima and media of pulmonary muscular arteries and arterioles.

Question 411

What is Eisenmenger complex, and how does it develop?

Answer 411

Eisenmenger complex occurs when pulmonary resistance becomes higher than systemic resistance, causing right-to-left shunting of blood and late cyanosis.

Question 412

What is a patent ductus arteriosus (PDA), and when does it occur?

Answer 412

A patent ductus arteriosus (PDA) occurs when the ductus arteriosus, a connection between the pulmonary trunk and the aorta, fails to close after birth.

Question 413

In which infants is PDA more common?

Answer 413

PDA is more common in premature infants and in cases of maternal rubella infection.

Question 414

What type of shunt does PDA cause, and what is the clinical presentation?

Answer 414

PDA causes a left-to-right shunt (from the aorta to the pulmonary trunk) and is non-cyanotic. The newborn presents with a machine-like murmur.

Question 415

How does the ductus arteriosus normally close after birth?

Answer 415

Normally, the ductus arteriosus closes within a few hours after birth via smooth-muscle contraction to form the ligamentum arteriosum.

Question 416

What substances sustain the patency of the ductus arteriosus during the fetal period?

Answer 416

Prostaglandin E (PGE) and low oxygen tension sustain the patency of the ductus arteriosus during the fetal period.

Question 417

Why is PGE used in certain heart defects like transposition of the great vessels?

Answer 417

PGE is used to keep the PDA open in certain heart defects, such as transposition of the great vessels.

Question 418

What substances promote the closure of the ductus arteriosus in premature birth?

Answer 418

PGE inhibitors (e.g., indomethacin), acetylcholine, histamine, and catecholamines promote the closure of the ductus arteriosus in a premature birth.

Question 419

When does the septation of the truncus arteriosus occur?

Answer 419

The septation of the truncus arteriosus occurs during week 8.

Question 420

What is the role of neural crest cells in the septation of the truncus arteriosus?

Answer 420

Neural crest cells migrate into the conotruncal and bulbar ridges of the truncus arteriosus, where they grow in a spiral fashion and fuse to form the aorticopulmonary (AP) septum.

Question 421

What does the aorticopulmonary (AP) septum do?

Answer 421

The AP septum divides the truncus arteriosus into the aorta and pulmonary trunk.

Question 422

What are the classic cyanotic congenital heart abnormalities related to?

Answer 422

These abnormalities are related to defects in the development of the aorticopulmonary septum.

Question 423

What causes the defects in the development of the aorticopulmonary septum?

Answer 423

The defects are caused by the failure of neural crest cells to migrate into the truncus arteriosus.

Question 424

What causes Tetralogy of Fallot?

Answer 424

Tetralogy of Fallot occurs when the aorticopulmonary (AP) septum fails to align properly and shifts anteriorly to the right.

Question 425

What type of shunting is seen in Tetralogy of Fallot, and what is the result?

Answer 425

Tetralogy of Fallot causes right-to-left shunting of blood, resulting in cyanosis.

Question 426

What does imaging typically show in cases of Tetralogy of Fallot?

Answer 426

Imaging typically shows a boot-shaped heart due to the enlarged right ventricle.

Question 427

What are the four major defects in Tetralogy of Fallot?

Answer 427

The four major defects are: - Pulmonary stenosis (most important) - Membranous interventricular septal defect - Right ventricular hypertrophy (develops secondarily) - Overriding aorta (receives blood from both ventricles)

Question 428

What causes Transposition of the Great Vessels?

Answer 428

Transposition of the great vessels occurs when the aorticopulmonary (AP) septum fails to develop in a spiral fashion, resulting in the aorta arising from the right ventricle and the pulmonary trunk arising from the left ventricle.

Question 429

What type of shunting is seen in Transposition of the Great Vessels, and what is the result?

Answer 429

Transposition of the great vessels causes right-to-left shunting of blood, resulting in cyanosis.

Question 430

What is the most common cause of severe cyanosis in newborns?

Answer 430

Transposition of the great vessels is the most common cause of severe cyanosis that persists immediately at birth.

Question 431

What does Transposition of the Great Vessels lead to in terms of circulation?

Answer 431

Transposition leads to the creation of two closed circulation loops.

Question 432

What defects are usually present in infants born with Transposition of the Great Vessels?

Answer 432

Infants born with this defect usually have other defects like PDA (patent ductus arteriosus), VSD (ventricular septal defect), or ASD (atrial septal defect), which allow mixing of oxygenated and deoxygenated blood to sustain life.

Question 433

What causes Persistent Truncus Arteriosus?

Answer 433

Persistent truncus arteriosus occurs when there is only partial development of the aorticopulmonary (AP) septum.

Question 434

What results from the partial development of the AP septum in Persistent Truncus Arteriosus?

Answer 434

The condition results in only one large vessel leaving the heart, which receives blood from both the right and left ventricles.

Question 435

What type of shunting occurs in Persistent Truncus Arteriosus, and what is the result?

Answer 435

Persistent truncus arteriosus causes right-to-left shunting of blood, resulting in cyanosis.

Question 436

Is there any additional defect associated with Persistent Truncus Arteriosus?

Answer 436

This defect is always accompanied by a membranous ventricular septal defect (VSD).

Question 437

Which congenital heart defects are considered non-cyanotic (left-to-right) at birth?

Answer 437

- Atrial septal defect - Ventricular septal defects - Patent ductus arteriosus

Question 437

Which congenital heart defects are considered cyanotic (right-to-left) at birth?

Answer 437

- Transposition of great vessels - Tetralogy of Fallot - Persistent truncus arteriosus

Question 437

What structures bound the superior and inferior parts of the mediastinum?

Answer 437

Superiorly, the mediastinum is continuous with the neck through the thoracic inlet. Inferiorly, it is closed by the diaphragm.

Question 437

What is the mediastinum?

Answer 437

The mediastinum is the central, midline compartment of the thoracic cavity, bounded anteriorly by the sternum, posteriorly by the 12 thoracic vertebrae, and laterally by the pleural cavities.

Question 437

Where are the sympathetic trunks located in relation to the mediastinum?

Answer 437

The sympathetic trunks are located paravertebrally, just outside the posterior mediastinum.

Question 437

What organs and structures are contained in the mediastinum?

Answer 437

The mediastinum contains most of the viscera of the thoracic cavities, except the lungs (and pleura) and the sympathetic trunk.

Question 438

What are the thoracic splanchnic nerves, and where do they enter?

Answer 438

The greater, lesser, and least thoracic splanchnic nerves carry preganglionic sympathetic fibers to the collateral (prevertebral) ganglia below the diaphragm. These nerves enter the posterior mediastinum after leaving the sympathetic trunks.

Question 439

How is the mediastinum divided into superior and inferior parts?

Answer 439

The mediastinum is divided into superior and inferior parts by a plane passing from the sternal angle (of Louis) anteriorly to the intervertebral disc between T4 and T5 posteriorly.

Question 440

What are the subdivisions of the inferior mediastinum?

Answer 440

The inferior mediastinum is subdivided into anterior, middle, and posterior mediastina.

Question 441

What is the anterior mediastinum?

Answer 441

The anterior mediastinum is the small interval between the sternum and the anterior surface of the pericardium.

Question 442

What does the anterior mediastinum contain?

Answer 442

The anterior mediastinum contains fat, areolar tissue, and the inferior part of the thymus gland.

Question 443

Where can a tumor of the thymus (thymoma) develop?

Answer 443

A thymoma can develop in the anterior or superior mediastinum.

Question 444

Where is the posterior mediastinum located?

Answer 444

The posterior mediastinum is located between the posterior surface of the pericardium and the T5-T12 thoracic vertebrae.

Question 445

What are the 4 vertically oriented structures coursing within the posterior mediastinum?

Answer 445

The four structures are the thoracic aorta, esophagus, thoracic duct, and azygos system of veins.

Question 446

What are the important branches of the thoracic (descending) aorta?

Answer 446

The important branches are the bronchial, esophageal, and posterior intercostal arteries.

Question 447

Where does the thoracic aorta pass through to become the abdominal aorta?

Answer 447

The thoracic aorta passes through the aortic hiatus at the T12 vertebral level to become the abdominal aorta.

Question 448

Where is the esophagus located relative to other structures?

Answer 448

The esophagus lies immediately posterior to the left primary bronchus and the left atrium.

Question 449

What are the plexuses that cover the esophagus?

Answer 449

The esophagus is covered by the anterior and posterior esophageal plexuses, derived from the left and right vagus nerves, respectively.

Question 450

Where does the esophagus pass through to enter the abdomen?

Answer 450

The esophagus passes through the esophageal hiatus at the T10 vertebral level.

Question 451

At which locations is the esophagus constricted?

Answer 451

The esophagus is constricted at (1) its origin from the pharynx, (2) posterior to the arch of the aorta, (3) posterior to the left primary bronchus, and (4) at the esophageal hiatus of the diaphragm.

Question 452

Where does the thoracic duct drain?

Answer 452

The thoracic duct drains into the junction of the left subclavian and internal jugular veins.

Question 453

Where does the thoracic duct arise from?

Answer 453

The thoracic duct arises from the cisterna chyli in the abdomen at vertebral level L1.

Question 454

Where does the azygos system of veins drain?

Answer 454

The azygos system drains the posterior and thoracic lateral wall.

Question 455

Where does the azygos vein empty into?

Answer 455

The azygos vein arches over the root of the right lung and empties into the superior vena cava above the pericardium.

Question 456

What is the function of the azygos system of veins?

Answer 456

The azygos system forms a collateral venous circulation between the inferior and superior vena cava.

Question 457

What does the middle mediastinum contain?

Answer 457

The middle mediastinum contains the heart, great vessels, and pericardium.

Question 458

Where is the superior mediastinum located?

Answer 458

It is located between the manubrium of the sternum anteriorly and the thoracic vertebrae T1–T4 posteriorly, with the parietal pleura and lungs forming the lateral boundary.

Question 459

What connects the superior mediastinum to the neck?

Answer 459

The thoracic inlet connects the superior mediastinum to the neck.

Question 460

What forms the inferior boundary of the superior mediastinum?

Answer 460

The horizontal plane through the sternal angle forms the inferior boundary.

Question 461

What are the main contents of the superior mediastinum?

Answer 461

The thymus, great arteries and veins associated with the upper heart, trachea, esophagus, vagus and phrenic nerves, and thoracic duct.

Question 462

Which mediastinum contains the pulmonary trunk and arteries?

Answer 462

The pulmonary trunk and arteries are located in the middle mediastinum, not the superior mediastinum.

Question 463

Where is the thymus located in the superior mediastinum?

Answer 463

It is located posterior to the manubrium, often atrophied in adults and replaced by fatty tissue.

Question 464

What is the relationship of the brachiocephalic veins in the superior mediastinum?

Answer 464

The right brachiocephalic vein descends vertically, while the left crosses obliquely posterior to the thymus. They join to form the superior vena cava.

Question 465

Where does the aortic arch begin and end?

Answer 465

The aortic arch begins and ends at the plane of the sternal angle, just inferior to the left brachiocephalic vein.

Question 466

What lies posterior to the trachea in the superior mediastinum?

Answer 466

The esophagus lies posterior to the trachea and courses posterior to the left primary bronchus to enter the posterior mediastinum.

Question 467

What is the role of the right and left vagus nerves in the superior mediastinum?

Answer 467

They contribute to the pulmonary and cardiac plexuses. The left vagus nerve gives rise to the left recurrent laryngeal nerve, which passes under the aortic arch and ligamentum arteriosum to ascend to the larynx.

Question 468

Where does the thoracic duct terminate?

Answer 468

It terminates at the junction of the left internal jugular vein and the left subclavian vein.

Question 469

What is the function of the phrenic nerves, and where do they pass in the mediastinum?

Answer 469

The phrenic nerves are the sole motor supply of the diaphragm and convey sensory information from the diaphragm and pleura. They pass through the middle mediastinum lateral to the fibrous pericardium and anterior to the root of the lung.

Question 470

What is coarctation of the aorta?

Answer 470

It is a narrowing of the aorta distal to the origin of the left subclavian artery.

Question 471

What are the two types of coarctation of the aorta?

Answer 471

Preductal coarctation (infantile type) and postductal coarctation (adult type).

Question 472

Where does preductal coarctation occur?

Answer 472

It occurs proximal to the ductus arteriosus (DA).

Question 473

What is the status of the ductus arteriosus in preductal coarctation?

Answer 473

The ductus arteriosus usually remains patent, allowing blood flow to the descending aorta and lower body.

Question 474

Where does postductal coarctation occur?

Answer 474

It occurs distal to the ductus arteriosus.

Question 475

What happens to the ductus arteriosus in postductal coarctation?

Answer 475

The ductus arteriosus usually closes and obliterates.

Question 476

How is blood supplied to the lower body in postductal coarctation?

Answer 476

Collateral circulation is provided by the intercostal arteries between the internal thoracic artery and the thoracic aorta.

Question 477

What are the characteristic blood pressure changes in postductal coarctation?

Answer 477

Patients have hypertension in the upper body (head, neck, and upper limbs) and hypotension with weak pulses in the lower limbs.

Question 478

What radiological finding is associated with postductal coarctation?

Answer 478

Costal notching on the lower border of the ribs due to the enlargement of intercostal arteries.

Question 479

Where does the left recurrent laryngeal nerve curve?

Answer 479

It curves under the aortic arch distal to the ligamentum arteriosum.

Question 480

What pathologies can damage the left recurrent laryngeal nerve?

Answer 480

Pathologies such as malignancy or aneurysm of the aortic arch can damage the nerve.

Question 481

What is the clinical consequence of damage to the left recurrent laryngeal nerve?

Answer 481

It results in paralysis of the left vocal folds.

Question 482

Why is the right recurrent laryngeal nerve less likely to be affected by aortic arch pathologies?

Answer 482

The right recurrent laryngeal nerve arises from the right vagus nerve in the root of the neck and passes under the subclavian artery, avoiding the aortic arch.

Question 483

What surgical procedure poses a risk to both the right and left recurrent laryngeal nerves?

Answer 483

Thyroid gland surgery may lesion either the right or left recurrent laryngeal nerve.

Question 484

What muscles are innervated by the musculocutaneous nerve?

Answer 484

All the muscles of the anterior compartment of the arm.

Question 485

What are the primary actions of the musculocutaneous nerve?

Answer 485

Elbow flexion and supination (biceps brachii).

Question 486

Which forearm muscles are innervated by the median nerve?

Answer 486

All muscles in the anterior compartment except for the flexor carpi ulnaris and the ulnar half of the flexor digitorum profundus.

Question 487

Which hand muscles are innervated by the median nerve?

Answer 487

Thenar compartment muscles and the lumbricals of digits 2 and 3.

Question 488

What actions does the median nerve perform in the forearm?

Answer 488

Flexion of the wrist and all digits, and pronation.

Question 489

What actions does the median nerve perform in the hand?

Answer 489

Thumb opposition, flexion of metacarpophalangeal (MP) joints, and extension of proximal (PIP) and distal (DIP) interphalangeal joints of digits 2 and 3.

Question 490

Which forearm muscles are innervated by the ulnar nerve?

Answer 490

1½ muscles: the flexor carpi ulnaris and the ulnar half of the flexor digitorum profundus.

Question 491

Which hand muscles are innervated by the ulnar nerve?

Answer 491

Hypothenar compartment muscles, interossei (palmar and dorsal), lumbricals of digits 4 and 5, and the adductor pollicis.

Question 492

What actions does the ulnar nerve perform in the hand?

Answer 492

- Weak wrist flexion and flexion of digits 4 and 5. - Abduction of digits 2–5 (Dorsal Interossei - DAB). - Adduction of digits 2–5 (Palmar Interossei - PAD). - Assists with MP flexion and IP extension of digits 4 and 5.

Question 493

Which muscles are innervated by the axillary nerve?

Answer 493

Deltoid and teres minor.

Question 494

What actions does the axillary nerve perform?

Answer 494

Shoulder abduction (from 15° to 110°) and lateral rotation of the shoulder.

Question 495

Which muscles are innervated by the radial nerve?

Answer 495

Posterior compartment muscles of the arm and forearm.

Question 496

What actions does the radial nerve perform?

Answer 496

Extension of the elbow, wrist, and MP joints; supination (via the supinator muscle).

Question 497

Which muscles are innervated by the dorsal scapular nerve?

Answer 497

Rhomboids.

Question 498

What is the primary action of the serratus anterior muscle, and which nerve innervates it?

Answer 498

The serratus anterior muscle protracts and rotates the scapula superiorly, and it is innervated by the long thoracic nerve.

Question 499

Which nerve innervates the supraspinatus and infraspinatus muscles?

Answer 499

The suprascapular nerve (C5-C6).

Question 500

What are the actions of the supraspinatus and infraspinatus muscles?

Answer 500

The supraspinatus abducts the shoulder (0–15°), and the infraspinatus laterally rotates the shoulder.

Question 501

Which muscle does the lateral pectoral nerve innervate?

Answer 501

Pectoralis major.

Question 502

Which muscles are innervated by the medial pectoral nerve?

Answer 502

Pectoralis major and minor.

Question 503

What muscle is innervated by the upper subscapular nerve?

Answer 503

Subscapularis.

Question 504

Which nerve innervates the latissimus dorsi muscle?

Answer 504

Middle subscapular (thoracodorsal) nerve.

Question 505

Which muscles are innervated by the lower subscapular nerve?

Answer 505

Subscapularis and teres major.

Question 506

Which nerve provides sensory innervation to the skin of the medial arm?

Answer 506

Medial brachial cutaneous nerve.

Question 507

Which nerve provides sensory innervation to the skin of the medial forearm?

Answer 507

Medial antebrachial cutaneous nerve.

Question 508

Q1: What is the origin of the femoral nerve?

Answer 508

A1: The femoral nerve originates from L2–L4 posterior divisions.

Question 509

Q2: Which muscles are innervated by the femoral nerve?

Answer 509

A2: The femoral nerve innervates the anterior compartment of the thigh, including quadriceps femoris, sartorius, and pectineus.

Question 510

Q3: What are the primary actions of the femoral nerve?

Answer 510

A3: The femoral nerve is responsible for extending the knee and flexing the hip.

Question 511

Q4: What is the origin of the obturator nerve?

Answer 511

A4: The obturator nerve originates from L2–L4 anterior divisions.

Question 512

Q5: Which muscles are innervated by the obturator nerve?

Answer 512

A5: The obturator nerve innervates the medial compartment of the thigh, including gracilis, adductor longus, adductor brevis, and the anterior portion of adductor magnus.

Question 513

Q6: What are the primary actions of the obturator nerve?

Answer 513

A6: The obturator nerve adducts the thigh and medially rotates the thigh.

Question 514

Q7: What is the origin of the tibial nerve?

Answer 514

A7: The tibial nerve originates from L4–S3 anterior divisions.

Question 515

Q8: Which muscles are innervated by the tibial nerve?

Answer 515

A8: The tibial nerve innervates the posterior compartment of the thigh (semimembranosus, semitendinosus, long head of biceps femoris, and posterior portion of adductor magnus), the posterior compartment of the leg (gastrocnemius, soleus, flexor digitorum longus, flexor hallucis longus, tibialis posterior), and the plantar muscles of the foot.

Question 516

Q9: What are the primary actions of the tibial nerve?

Answer 516

A9: The tibial nerve flexes the knee, extends the thigh, plantarflexes the foot (S1–2), flexes the digits, and contributes to inversion.

Question 517

Q10: What is the origin of the common fibular nerve?

Answer 517

A10: The common fibular nerve originates from L4–S2 posterior divisions.

Question 518

Q11: Which muscle is innervated by the common fibular nerve?

Answer 518

A11: The common fibular nerve innervates the short head of the biceps femoris.

Question 519

Q12: What is the primary action of the common fibular nerve?

Answer 519

A12: The common fibular nerve flexes the knee.

Question 520

Q13: Which muscles are innervated by the superficial fibular nerve?

Answer 520

A13: The superficial fibular nerve innervates the lateral compartment of the leg, including fibularis longus and fibularis brevis.

Question 521

Q14: What is the primary action of the superficial fibular nerve?

Answer 521

A14: The superficial fibular nerve is responsible for eversion.

Question 522

Q15: Which muscles are innervated by the deep fibular nerve?

Answer 522

A15: The deep fibular nerve innervates the anterior compartment of the leg, including tibialis anterior, extensor hallucis, extensor digitorum, and fibularis tertius.

Question 523

Q16: What are the primary actions of the deep fibular nerve?

Answer 523

A16: The deep fibular nerve dorsiflexes the foot (L4–5), extends the digits, and contributes to inversion.

Question 524

What is the altered sensation caused by an axillary nerve lesion?

Answer 524

Lateral arm.

Question 525

What motor weakness is associated with an axillary nerve lesion?

Answer 525

Abduction at the shoulder.

Question 526

What are common causes of an axillary nerve lesion?

Answer 526

Surgical neck fracture of the humerus and dislocated humerus.

Question 527

What is the altered sensation caused by a musculocutaneous nerve lesion?

Answer 527

Lateral forearm.

Question 528

What motor weakness is associated with a musculocutaneous nerve lesion?

Answer 528

Flexion of the forearm and supination.

Question 529

Is there a common sign of a musculocutaneous nerve lesion?

Answer 529

Rarely lesioned.

Question 530

What is the altered sensation caused by a radial nerve lesion?

Answer 530

Dorsum of hand over the first dorsal interosseous and anatomic snuffbox.

Question 531

What motor weakness is associated with a radial nerve lesion?

Answer 531

Wrist extension, metacarpophalangeal extension, and supination.

Question 532

What is a common sign of a radial nerve lesion?

Answer 532

Wrist drop.

Question 533

What are common causes of a radial nerve lesion?

Answer 533

Saturday night palsy, midshaft fracture of the humerus, subluxation of the radius, and dislocated humerus.

Question 534

What is the altered sensation caused by a median nerve lesion?

Answer 534

Lateral 3½ digits and the lateral palm.

Question 535

What motor weakness is associated with a median nerve lesion?

Answer 535

Wrist flexion, finger flexion, pronation, and thumb opposition.

Question 536

What are common signs of a median nerve lesion?

Answer 536

Ape hand, hand of benediction, and ulnar deviation at the wrist.

Question 537

What are common causes of a median nerve lesion?

Answer 537

Carpal tunnel compression, supracondylar fracture of the humerus, and pronator teres syndrome.

Question 538

What is the altered sensation caused by an ulnar nerve lesion?

Answer 538

Medial 1½ digits and the medial palm.

Question 539

What motor weakness is associated with an ulnar nerve lesion?

Answer 539

Wrist flexion, finger spreading, thumb adduction, and finger extension.

Question 540

What are common signs of an ulnar nerve lesion?

Answer 540

Claw hand and radial deviation at the wrist.

Question 541

What are common causes of an ulnar nerve lesion?

Answer 541

Fracture of the medial epicondyle of the humerus, fracture of the hook of hamate, and fracture of the clavicle.

Question 542

What is the dermatome paresthesia for C5?

Answer 542

Lateral border of the upper arm.

Question 543

Which muscles are affected in a C5 lesion?

Answer 543

Deltoid, rotator cuff, serratus anterior, biceps, brachioradialis.

Question 544

What reflex test is used for a C5 lesion?

Answer 544

None.

Question 545

What are common causes of a C5 lesion?

Answer 545

Upper trunk compression.

Question 546

What is the dermatome paresthesia for C6?

Answer 546

Lateral forearm to the thumb.

Question 547

Which muscles are affected in a C6 lesion?

Answer 547

Biceps, brachioradialis, brachialis, supinator.

Question 548

What reflex test is used for a C6 lesion?

Answer 548

Biceps tendon.

Question 549

What are common causes of a C6 lesion?

Answer 549

Upper trunk compression.

Question 550

What is the dermatome paresthesia for C8?

Answer 550

Medial forearm to the little finger.

Question 551

Which muscles are affected in a C8 lesion?

Answer 551

Finger flexors, wrist flexors, hand muscles.

Question 552

What reflex test is used for a C8 lesion?

Answer 552

None.

Question 553

What are common causes of a C8 lesion?

Answer 553

Lower trunk compression.

Question 554

What is the dermatome paresthesia for T1?

Answer 554

Medial arm to the elbow.

Question 555

Which muscles are affected in a T1 lesion?

Answer 555

Hand muscles.

Question 556

What reflex test is used for a T1 lesion?

Answer 556

None.

Question 557

What are common causes of a T1 lesion?

Answer 557

Lower trunk compression.

Question 558

Q: Which nerve is associated with the first pharyngeal arch?

Answer 558

A: Trigeminal nerve (mandibular branch).

Question 559

Q: What muscles are derived from the first pharyngeal arch?

Answer 559

A: Four muscles of mastication (masseter, temporalis, lateral pterygoid, medial pterygoid) plus digastric (anterior belly), mylohyoid, tensor tympani, and tensor veli palatini.

Question 560

Q: What skeletal structures are derived from the first pharyngeal arch?

Answer 560

A: Maxilla, mandible, incus, and malleus.

Question 561

Q: Which nerve is associated with the second pharyngeal arch?

Answer 561

A: Facial nerve (cranial nerve VII).

Question 562

Q: What muscles are derived from the second pharyngeal arch?

Answer 562

A: Muscles of facial expression, digastric (posterior belly), stylohyoid, and stapedius.

Question 563

Q: What skeletal structures are derived from the second pharyngeal arch?

Answer 563

A: Stapes, styloid process, and the lesser horn and upper body of the hyoid bone.

Question 564

Q: Which nerve is associated with the third pharyngeal arch?

Answer 564

A: Glossopharyngeal nerve (cranial nerve IX).

Question 565

Q: What muscle is derived from the third pharyngeal arch?

Answer 565

A: Stylopharyngeus muscle.

Question 566

Q: What skeletal structures are derived from the third pharyngeal arch?

Answer 566

A: Greater horn and lower body of the hyoid bone.

Question 567

Q: Which nerve is associated with the fourth and sixth pharyngeal arches?

Answer 567

A: Vagus nerve (cranial nerve X).

Question 568

Q: What muscles are derived from the fourth pharyngeal arch?

Answer 568

A: Cricothyroid muscle, soft palate, and pharyngeal muscles (5 muscles).

Question 569

Q: What skeletal structure is derived from the fourth pharyngeal arch?

Answer 569

A: Thyroid cartilage.

Question 570

Q: What muscles are derived from the sixth pharyngeal arch?

Answer 570

A: Intrinsic muscles of the larynx (except cricothyroid muscle).

Question 571

Q: What skeletal structures are derived from the sixth pharyngeal arch?

Answer 571

A: All other laryngeal cartilages.

Question 572

Q: What is derived from the first pharyngeal pouch?

Answer 572

A: Epithelial lining of the auditory tube and middle ear cavity.

Question 573

Q: What is derived from the second pharyngeal pouch?

Answer 573

A: Epithelial lining of the crypts of the palatine tonsil.

Question 574

Q: What are the derivatives of the third pharyngeal pouch?

Answer 574

A: Inferior parathyroid gland and thymus.

Question 575

Q: What are the derivatives of the fourth pharyngeal pouch?

Answer 575

A: Superior parathyroid gland and C-cells of the thyroid (parafollicular cells).

Question 576

Question: What structures derive from the telencephalon?

Answer 576

Answer: Cerebral hemispheres and most of the basal ganglia.

Question 577

Question: Which brain vesicle gives rise to the thalamus, hypothalamus, subthalamus, epithalamus (pineal gland), retina, and optic nerve?

Answer 577

Answer: The diencephalon.

Question 578

Question: What structure derives from the mesencephalon?

Answer 578

Answer: The midbrain.

Question 579

Question: What structures derive from the metencephalon?

Answer 579

Answer: The pons and cerebellum.

Question 580

Question: What structures derive from the myelencephalon?

Answer 580

Answer: The spinal cord and medulla.

Question 581

Question: Which neural canal remnant is associated with the telencephalon?

Answer 581

Answer: The lateral ventricles.

Question 582

Question: Which neural canal remnant is associated with the diencephalon?

Answer 582

Answer: The third ventricle.

Question 583

Question: Which neural canal remnant is associated with the mesencephalon?

Answer 583

Answer: The cerebral aqueduct.

Question 584

Question: Which neural canal remnant is associated with the metencephalon?

Answer 584

Answer: The fourth ventricle.

Question 585

Question: Which neural canal remnant is associated with the myelencephalon?

Answer 585

Answer: The central canal.

Question 586

Question: What causes anencephaly?

Answer 586

Answer: Failure of the anterior neuropore to close.

Question 587

Question: What are the clinical features of anencephaly?

Answer 587

Answer: The brain does not develop, it is incompatible with life, and there is increased AFP during pregnancy and AChE.

Question 588

Question: What is spina bifida occulta?

Answer 588

Answer: Failure to induce bone growth around the spinal cord, with no increase in AFP. It is asymptomatic and often presents as a tuft of hair over the defect.

Question 589

Question: How does spina bifida with meningocele differ from spina bifida occulta?

Answer 589

Answer: In spina bifida with meningocele, the meninges protrude through the vertebral defect, causing an increase in AFP.

Question 590

Question: What is associated with spina bifida with meningomyelocele?

Answer 590

Answer: Meninges and the spinal cord protrude through the vertebral defect. It is associated with Arnold-Chiari Type II and shows an increase in AFP.

Question 591

Question: What is the most severe form of spina bifida?

Answer 591

Answer: Spina bifida with myeloschisis, where the spinal cord can be seen externally. It shows an increase in AFP and AChE.

Question 592

Question: What is Arnold-Chiari malformation Type I?

Answer 592

Answer: It is the most common type, mostly asymptomatic in children, with downward displacement of the cerebellar tonsils through the foramen magnum. It is frequently associated with syringomyelia.

Question 593

Question: What differentiates Arnold-Chiari malformation Type II from Type I?

Answer 593

Answer: Type II is more often symptomatic, with downward displacement of the cerebellar vermis, compression of the IV ventricle leading to obstructive hydrocephalus, and frequent lumbar meningomyelocele.

Question 594

Question: What causes Dandy-Walker malformation?

Answer 594

Answer: Failure of the foramina of Luschka and Magendie to open, leading to dilation of the IV ventricle, agenesis of the cerebellar vermis, and splenium of the corpus callosum.

Question 595

Question: What causes hydrocephalus?

Answer 595

Answer: Most often caused by stenosis of the cerebral aqueduct, leading to CSF accumulation in ventricles and subarachnoid space, and increased head circumference.

Question 596

Question: What is holoprosencephaly?

Answer 596

Answer: Incomplete separation of the cerebral hemispheres, with one ventricle in the telencephalon, often seen in Trisomy 13 (Patau).

Question 597

Question: What structures are derived from the surface ectoderm?

Answer 597

Answer: Epidermis, hair, nails, inner ear (external ear), enamel of teeth, lens of the eye, anterior pituitary (Rathke's pouch), and parotid gland.

Question 598

Question: What structures are derived from the neuroectoderm?

Answer 598

Answer: Central nervous system, retina and optic nerve, pineal gland, neurohypophysis, astrocytes, and oligodendrocytes (CNS myelin).

Question 599

Question: Which germ layer gives rise to the adrenal medulla?

Answer 599

Answer: Neural crest (ectoderm).

Question 600

Question: What are the derivatives of the neural crest?

Answer 600

Answer: Adrenal medulla, ganglia (sensory unipolar and autonomic postganglionic), pigment cells (melanocytes), Schwann cells (PNS myelin), meninges (pia and arachnoid mater), pharyngeal arch cartilage (first arch syndromes), odontoblasts, parafollicular (C) cells, aorticopulmonary septum (Tetralogy of Fallot), and endocardial cushions (Down syndrome).

Question 601

Question: Which germ layer forms smooth, cardiac, and skeletal muscle?

Answer 601

Answer: Mesoderm.

Question 602

Question: What connective tissues are derived from the mesoderm?

Answer 602

Answer: All serous membranes, bone, cartilage, blood, lymph, cardiovascular organs, adrenal cortex, gonads and internal reproductive organs, spleen, kidney and ureter, and dura mater.

Question 603

Question: What epithelial parts are derived from the endoderm?

Answer 603

Answer: Tonsils, thymus, pharynx, larynx, trachea, bronchi, lungs, urinary bladder, urethra, tympanic cavity, auditory tube, and GI tract.

Question 604

Question: Which germ layer gives rise to the liver and pancreas?

Answer 604

Endoderm.

Question 605

Question: What parenchyma are derived from the endoderm?

Answer 605

Answer: Liver, pancreas, tonsils, thyroid gland, parathyroid glands, glands of the GI tract, submandibular gland, and sublingual gland.

Question 606

Question: What germ layer forms the adrenal cortex?

Answer 606

Mesoderm.