Uworld34 Flashcards
What is the haldane and Bohr effect?
The binding of O2 to hemoglobin increases the affinity for binding of subsequent O2 molecules (cooperative binding). In the lungs, the binding of O2 to hemoglobin drives the release of H+ and CO2 from hemoglobin (Haldane effect).
In the peripheral tissues, high concentrations of CO2 and H+ facilitate O2 unloading from hemoglobin (Bohr effect)
Risk factors for aortic dissection versus aortic aneurysms
Hypertension is the single most important risk factor for the development of intimal tears leading to aortic dissection.
Hypertension, smoking, diabetes mellitus, and hypercholesterolemia are all major risk factors for atherosclerosis, which predisposes more to aortic aneurysm formation than aortic dissection.
MOA of amiodarone
Amiodarone primarily functions as a class III antiarrhythmic, inhibiting the delayed rectifier potassium current to slow ventricular repolarization and prolong the QT interval.
It also inhibits fast sodium channels (class I effect) to slow ventricular depolarization and prolong QRS complex duration.
Beta blockade (class II effect) and inhibition of slow L-type calcium channels (class IV effect) slow conduction in the sinus node and atrioventricular node causing decreased sinus rate and a prolonged PR interval
What is the clinical presentation of tertiary syphilis?
cardiovascular involvement and gummas.
Gummas are necrotizing granulomas occuring on the skin, mucosa, subcutaneous tissue, and bones and within other organs. Neurosyphilis can occur at any stage of infection.
What is observer bias?
occurs when the investigator’s evaluation is affected by preconceived expectations or prior knowledge, typically leading to overestimation of the disease association or treatment effects. This type of bias can be reduced by conducting a blinded study in which observers are unaware of study details and patient characteristics that could unduly influence them.
Chronic adminstration of GnRH agonists (leuprolide) suppresses?
pituitary LH release and leads to reduced production of testosterone.
Lower levels of circulating testosterone produce a clinical effect similar to that of surgical orchiectomy and can lead to accelerated bone loss and increased risk for osteoporosis
Restrictive cardiomyopathy can be caused by?
infiltrative diseases (eg, amyloidosis, sarcoidosis, hemochromatosis) and often results in diastolic heart failure due to ventricular hypertrophy with impaired ventricular filling.
Cardiac amyloidosis is characterized histologically by areas of myocardium infiltrated by an amorphous and acellular pink material (amyloid)
What is the effect of pregnancy and the pituitary?
High estrogen levels during pregnancy cause enlargement of the pituitary gland without a proportional increase in blood supply.
Peripartum hypotension can cause ischemic necrosis of the pituitary leading to panhypopituitarism (Sheehan syndrome). Patients commonly develop failure of lactation due to deficiency of prolactin.
What are the diagnostic tests for syphilis?
Syphilis is caused by the spirochete Treponema pallidum. Confirmation of the diagnosis requires 2 forms of serologic testing to prevent false-positive results.
Nontreponemal tests (eg, rapid plasma reagin, VDRL) evaluate for anticardiolipin antibodies (nonspecific); treponemal tests evaluate for antibodies targeted against T pallidum
What are the watershed areas of the large intestine?
The splenic flexure and rectosigmoid junction lie between regions of perfusion of major arteries.
These “watershed” areas are susceptible to ischemic damage during hypotensive states, especially in patients with underlying arterial insufficiency
Location of the caudate
The head of the caudate lies in the inferolateral wall of the frontal horn of the lateral ventricle.
It is separated from the globus pallidus and putamen by the internal capsule.
Atrophy of the caudate nuclei with enlargement of the lateral ventricles is characteristic of Huntington disease and can be observed on neuroimaging
What is hereditary hemorrhagic telangiectasia?
presents with mucocutaneous telangiectasias, epistaxis, and visceral arteriovenous malformations (liver, lung, brain).
Lung involvement includes pulmonary AVMs (digital clubbing, platypnea) and pulmonary hypertension (a loud P2) due to high output heart failure from underlying systemic AVMs.
Treatment of organophosphate poisoning?
Organophosphates inhibit cholinesterase in both muscarinic and nicotinic cholinergic synapses, leading to decreased acetylcholine degradation and overstimulation of the corresponding receptors.
Atropine reverses muscarinic effects but does not prevent the development of nicotinic effects such as muscle paralysis.
Pralidoxime is a cholinesterasae-reactiviting agent that allows for degradation of excess acetylcholine and treats both the muscarinic and nicotinic effects of organophosphates
Function of germinal centers
Germinal centers are the sites where activated B cells proliferate and undergo affinity maturation during generation of humoral immune response.
The formation of multiple germinal centers is typically marked by lymphadenopathy, pain, and inflammation in the affected lymph node due to cellular recruitment and the release of inflammatory cytokines
Digoxin toxicity presents with?
cardiac arrhythmias and nonspecific gastrointestinal (nausea, vomiting), neurological (confusion, weakness), and visual symptoms.
Elevated potassium is another sign of toxicity and is caused by inhibition of Na-K-ATPase pumps
Initial empiric treatment of coagulase-negative staphylococcal infection should include?
vancomycin due to widespread methicillin resistance, especially in nosocomial infections.
If susceptibility results indicate a methicillin-susceptible isolate, vancomycin can be switched to nafcillin or oxacillin
Lateral ankle sprain is due to?
inversion of a plantar-flexed foot and most commonly involves the anterior talofibular ligament.
Stronger forces can cause joint instability by injuring additional ligaments.
Neonates versus adult body water
Neonates have a higher proportion of body water compared to adults. This can result in lower plasma concentrations of water-soluble drugs if they are administered at the same weight-based dosage as given to adult patients
Pleural effusion causes what to tactile fremitus and breath sounds
Fluid in the pleural space acts to insulate sound vibrations that originate in the airways; therefore, pleural effusion causes decreased tactile fremitus and decreased intensity of breath sounds.
The high density of pleural fluid compared to normal lung tissue also causes dullness to percussion
What is atopic dermatitis (eczema)?
Atopic dermatitis is a common, chronic inflammatory disorder caused by impairment of the skin’s barrier funciton.
Eczema presents with pruritus and erythematous papules and plaques and is associated with other atopic disease, such as allergic rhinitis and asthma
Stress related mucosal disease is usually caused by?
local ischemia in the setting of severe physiologic stress (eg, shock, extensive burns, sepsis, severe trauma). Ulcers arising in the setting of severe trauma/burns are called Curling ulcers. Ulcers arising from intracranial injury are caused by direct vagal stimulation and are called Cushing ulcers
What are risk factors for candidemia?
The presence of a central vascular catheter and receipt of parenteral nutrition are risk factors for candidemia.
Candida display a morphology of branching pseudohyphae with blastoconidia
What is the main mechanism underlying all types of renal stones
Urine supersaturation is the main mechanism underlying all types of renal stones.
Low fluid intake increases the concentration of stone-forming agents, thereby promoting stone formation. All patients with nephrolithiasis should be advised to maintain adequate fluid intake
What is a lipoma?
Lipomas are common, benign tumors that arise from the subcutaneous fat and present as soft, mobile masses that are stable or enlarge slowly over time. The diagnosis is usually made clinically, but histopath shows well-differentiated, mature adipocytes with a fibrous capsule
What is a pleural effusion?
a collection of fluid between the visceral pleura that lines the lungs and the parietal pleura that lines the thoracic cavity.
The fluid acts to insulate vibrations and sounds that originate in the airways of the lung; therefore, tactile fremitus and breath sounds are decreased over a pleural effusion. Dullness to percussion is also present.
What is locked in syndrome
Ischemic injury to the bilateral ventral pons can lead to locked-in syndrome, a condition in which patients are unable to move or speak (due to interruption of the corticospinal and corticobulbar tracts) but retain consciousness, sensation, eye opening, and vertical eye movements
What is hematogenous osteomyelitis?
occurs most commonly in children. It usually affects the metaphysis of long bones due to the presence of slow-flowing sinusoids that are conducive to bacterial seeding. Fever and refusal to bear weight are common in young children who are unable to localize the pain.
What is responsible for the thrombotic and thromboembolic complications of nephrotic syndrome?
Neprotic syndrome is a hyper coagulable state. Sudden-onest abdominal or flank pain, hematuria and left sided varicoceles suggest renal vein thrombosis, a well known complication of nephrotic syndrome.
Loss of anticoagulant factors, especially antithrombin III, is responsible for the thrombotic and thromboembolic complications of nephrotic syndrome
Mutations of fas receptor leads to
The fas receptor acts to initiate the extrinsic pathway of apoptosis. Mutations involving the Fas receptor or Fas ligand can prevent apoptosis of autoreactive lymphocytes, thereby increasing the risk of autoimmune disorders such as systemic lupus erythematosus
What processes occur in the mitochondria versus the cytosol?
Cellular compartmentalization allows multiple biochemical processes to occur simultaneously at maximum efficiency.
Beta-oxidation of fatty acids, the TCA cycle, and the carboxylation of pyruvate (gluconeogenesis) all occur within the mitochondria.
The enzymes responsible for glycolysis, fatty acid synthesis, and the pentose phosphate pathway reside in the cytosol
What can increase GFR and decrease it?
Increases in capillary hydrostatic pressure or the Bowman’s space oncotic pressure will increase GFR, while increases in capillary oncotic pressure or Bowman’s space hydrostatic pressure will decrease GFR.
The filtration fraction can be calculated by dividing the GFR by the renal plasma flow (RPF). Increases in GFR or decrease in RPF will increase the FF.
What is first line pharmacotherapy for moderate to severe alcohol use disorder?
The opioid antagonist natrexone, and works by preventing the reinforcing effects of alcohol use.
What is poststreptococcal glomerulonephritis?
the most common cause of nephritic syndrome in children.
Light microscopy demonstrates enlarged, hypercellular glomeruli.
Labs: elevated antistreptococcal antibodies (eg, antistreptolysin O, anti-DNase B) and decreased C3 and total complement levels. C4 levels are usually normal.
What is the pathogenesis of e coli sepsis?
Pathogenesis of e coli sepsis involved the release of lipopolysaccharide (endotoxin) from bacterial cells.
Lipid A is the major virulence factor of lipopolysaccarides that induces macrophages to release cytokines (IL-1, tumor necrosis factor-alpha), leading to the manifestations of septic shock (end organ dysfunction)
What is seen in left sided heart failure
Left sided heart failure is common following myocardial infarction affecting the left ventricle. The resulting accumulation of edema in the pulmonary interstitium makes the lungs heavy and stiff, restricting inspiratory expansion and decreasing lung compliance.
Severe hypertension in retinal precapillary arterioles causes?
endothelial disruption, leakage of plasma into the arteriolar wall, and fibrinous necrosis. The necrotic vessels can then bleed into the nerve fiber layer, which can be seen on examination as dot or flamed shaped hemorrhages
Inflammatory bowel disease, especially ulcerative pancolitis, is associated with a significant risk for?
colorectal carcinoma. Compared with sporadic colorectal cancer, colitis-associated colorectal cancer is more likely to occur at a younger age, is typically more aggressive with a higher histopathologic grade, often evolves from flat (nonpolypoid) lesions, and is frequently multifocal.
patients should be monitored regularly via colonoscopy with random biopsies
What is the most common cause of familial dilated cardiomyopathy?
Autosomal dominant mutations in the TTN gene, which encodes for the sarcomere protein titin
What is seen in orbitofrontal cortex injury?
Patients with orbitofrontal cortex injury often experience personality changes, disinhibition, and irritability secondary to impairment of the behavioral and emotional modulatory systems
What is dumping syndrome?
The pyloric sphincter prevents incompletely digested hyperosmolar food particles from entering the intestines too rapidly; when the sphincter is bypassed or surgically removed, dumping syndrome may occur.
Symptoms are related to excessive intestinal fluid (eg, abdominal cramps, diarrhea, nausea), vasomotor hyperactivity (eg, diaphoresis, palpitations, flushing) and intravascular volume depletion (eg, hypotension, tachycardia)
