Uworld29 Flashcards

Question

Innervation of external hemorrhoids

Answer 1

External hemorrhoids, which originate below the dentate line, are covered by modified squamous epithelium and have cutaneous (somatic) nervous innervation from the inferior rectal nerve, a branch of the pudendal nerve.

Answer 2

Menopause occurs on average at age 51 and is diagnosable retrospectively after 12 months of amenorrhea. An elevated serum FSH level confirms the diagnosis.

Answer 3

the inferior mesenteric and internal iliac lymph nodes.

Answer 4

inguinal nodes.

Answer 5

Growth hormone binds to cell surface receptors, leading to intracellular activation of the JAK-STAT pathway. Cytokines (eg, interferon) and hematopoietic growth factors (eg, erythropoietin, G-CSF) also use this pathway.

Answer 6

TNF-alpha is released from activated macrophages and is one of the most important mediators of the systemic inflammatory response in sepsis. Other cytokines responsible for inducing the systemic inflammatory response include IL-1 and IL-6

Answer 7

a hypermetabolic response that results in an increased basal metabolic rate and often lean muscle wasting. Administration of oxandrolone, a synthetic testosterone analogue, enhances muscle protein synthesis and decreases protein catabolism, reducing lean muscle loss.

Answer 8

IgG4 antibodies to the phospholipase A2 receptor, which might play a role in the development of the disease. Antibody titers are useful for diagnosis and correlate with disease activity.

Answer 9

Incomplete involution of the mammary ridge during fetal development can lead to an accessory nipple, a well-circumscibed, hyperpigmented papule located anywhere from the axilla to the thigh. Similar to hormone induced changes in normal breast tissue (eg, due to puberty/menses), they may grow larger and become tender/swollen

Answer 10

The adrenal cortex produces estrogen precursors (eg, androstenedione, dehydroepiandristerone (DHEA), DHEA sulfate, which are subsequently aromatized to estrogens in peripheral tissues In men with hypogonadism, the resulting elevation in the estrogen/testosterone ratio can produce gynecomastia.

Answer 11

supersaturation of the bile with bilirubin, which precipitates with calcium to form calcium bilirubinate stones. This typically occurs in the setting of chronic hemolysis (eg, sickle cell disease) or altered enterohepatic circulation of bilirubin (eg, Crohn disease, ileal resection)

Answer 12

Estrogen induced cholesterol hypersecretion and progesterone induced gallbladder hypomotility

Answer 13

Chelation therapy with deferoxamine. Deferoxamine prevents iron-induced cardiotoxicity and congestive heart failure from developing in this patient population.

Answer 14

truncal and gait ataxia due to impaired modulation of the medial-descending moto systems. Involvement of the lower vermis and the flocculonodular lobe also causes vertigo/nystagmus due to dysregulation of the vestibular nuclear complex.

Answer 15

hemorrhage from the high-pressure bronchial circulation. Bronchiectasis is a common etiology because chronic airway inflammation causes hypertrophied bronchial arteries that are prone to rupture with coughing.

Answer 16

The combination of fixed segmental loss of upper extremity pain and temperature sensations, upper extremity lower motor neuron signs, and/or lower extremity upper motor neuron signs in the setting of scoliosis suggests syringomyelia.

Answer 17

Ectopic production of antidiuretic hormone from malignancy can lead to the syndrome of inappropriate ADH secretion, a condition of impaired urinary water excretion. This condition manifests with low serum osmolality, hyponatremia, high urine osmolality, and high urine sodium concentration.

Answer 18

Delayed cerebral ischemia due to cerebral vasopasm usually presents 3-12 days after the initial subarachnoid hemorrhage with an acute change in mental status and/or new focal neurological deficits. Nimodipine, a selective calcium channel blocker, improves outcomes in patients with cerebral vasospasm by inducing cerebral vasodilation and decreasing calcium-dependent excitotoxicity.

Answer 19

Medication induced esophagitis is a common adverse effect of bisphosphonates. Bisphosphonates are also associated with increased risk of osteonecrosis of the jaw and atypical femoral fractures.

Answer 20

a checkpoint inhibitor that downregulates the cytotoxic T cell response. Neoplastic cells often exploit this receptor via the overexpression of PD-1 ligand. PD-1 receptor inhibitors (eg, pembrolizumab) restore the T cell response, allowing cytotoxic T cells to invade the tumor and induce apoptosis of neoplastic cells

Answer 21

Rotavirus is a common cause of self-limited childhood diarrhea in unvaccinated people. It infects villous enterocytes in the duodenum and proximal jejunum and results in villous blunting, proliferation of secretory crypt cells, and a loss of brush border enzymes; this results in watery diarrhea without fecal leukocytes

Answer 22

represents the excess risk in the exposed population that can be attributed to the risk factor. ARPexposed = 100 x [(RR-1)/RR]

Answer 23

progressive left ventricular dilation and worsening contractile dysfunction. Because much of this remodeling is driven by neurohormonal signaling via angiotensin II, ACE inhibitors (eg, lisinopril) reduce deleterious cardiac remodeling following myocardial infarction, minimizing LV dilation and helping preserve contractile function

Answer 24

weakened pelvic floor muscle support that often occurs due to chronically increased intraabdominal pressure (eg, obesity, chronic cough, prior pregnancies)

Answer 25

twisting of the testis around the spermatic cord (containing the gonadal artery), which can eventually lead to ischemia. The gonadal arteries arise from the abdominal aorta. The right gonadal vein drains directly into the inferior vena cava while the left gonadal vein drains into the left renal vein.

Answer 26

a transient increase in glomerular filtration (hyperfiltration). As diabetic nephropathy progresses, glomerular filtration falls, with a concurrent increase in urine albumin loss.

Answer 27

Constipation is the most common side effect of opiate therapy and occurs due to the binding of mu-opioid receptors in the GI tract, which decreases intestinal motility and inhibits ion and fluid secretion. Methylnatrexone, a peripherally acting mu-opioid receptor antagonist that does not cross the blood brain barrier, can alleviate opioid induced constipation without inducing opiate related withdrawal symptoms

Answer 28

Associated with congenital anomalies of the aorta, most commonly bicuspid aortic valve. A bicuspid aortic valve typically creates an early systolic click over the right upper sternal border, often with a faint ejection murmur. The abnormal structure and altered hemodynamics surrounding the valve accelerate age-related valvular calcification, commonly leading to aortic stenosis or, less commonly, aortic regurg.

Answer 29

indicates where there is a negative (r<0) or positive (r>0) linear relationship between 2 variables. The closer r is to -1 or 1, the stronger the linear relationship. A statistically significant (ie, p value < significance level) linear relationshop between 2 variables does not imply that the relationship is causal.

Answer 30

the most common hormonally active pituitary adenomas. The excess prolactin produced by these tumors can cause galactorrhea and amenorrhea in premenopausal women. With a large mass, visual changs and headaches may occur due to compression of the optic chiasm

Answer 31

Eosinophils have bilobed nuclei and numerous eosinophilic granules in the cytoplasm and are important in allergic disease and defense against parasitic infection. The eosinophilic granules predominantly contain major basic protein, which acts as a potent antihelminthic toxin. Major basic protein also damages epithelial and endothelial cells and is a major cause of chronic lung damage in asthma

Answer 32

insufficient development of the interventricular septum and commonly presents with a holosystolic murmur at the left lower sternal border as pulmonary vascular resistance decline in the neonatal period. Presentation varies from asymptomatic murmur (small defect) to heart failure (large defect)

Answer 33

elevated residual volume (air trapping) elevated total lung capacity (hyperinflation) and reduced forced vital capacity

Answer 34

increase cerebral blood flow. It is an undesirable effect as it results in increased ICP. Other important effects of inhalation anesthetics are myocardial depression, hypotension, respiratory depression and decreased renal function

Answer 35

the fragile germinal matrix in infants born before 32 weeks gestation and/or with birth weight <1500 g (3 lb 5 oz) It is a common complication of prematurity that can lead to long term neurodevelopment impairment

Answer 36

AD disorder caused by germline mutation to the tumor suppressor gene adenomatous polyposis coli. Patients with FAP develop hundreds or thousands of colonic polyps; lifetime risk of colon cancer is close to 100%

Answer 37

anticoagulants that block the active site of factor Xa, which leads to reduced conversion of prothrombin to thrombin. This class of meds is administered orally and requires no drug level monitoring.

Answer 38

often presents in young women with the insidious onset of respiratory symptoms (eg, cough, dyspnea, chest pain) accompanied by fatigue, fever, and weight loss. Histo: noncaseating granulomas, which consist of aggregates of epitheloid macrophages, frequently with multinucleated giant cells

Answer 39

causes hereditary fructose intolerance. This disease manifests after introduction of fructose into the diet with vomiting and hypoglycemia about 20-30 minutes after fructose ingestion. These infants can present with failure to thrive, jaundice, and hepatomegaly.

Answer 40

involves an autoimmune response (T cell and antibody-mediated) targeting oligodendrocytes and myelin in the central nervous system, leading to slowed nerve conduction with neurologic deficits.

Answer 41

Benign lymph node enlargement in response to antigenic stimulation is associated with a polyclonal proliferation of lymphocytes. A monoclonal lymphocytic proliferation is strong evidence of malignancy.

Answer 42

umbilical cord inflammation with abscess-like foci of necrosis

Answer 43

pneumonia because cigarette smoke affects alveolar macrophage function and impairs mucociliary clearance.

Answer 44

Essential tremor is the most common movement disorder. Patients experience a slowly progressice, symmetric postural and/or kinetic tremor that most commonly affects the upper extremities. Essential tremor is often inherited in an autosomal dominant fashion (referred to as familial tremor). First-line treatment is the nonspecific beta-adrenergic antagonist propranolol.

Answer 45

Spinal stenosis occurs most commonly in the lumbar region and presents with posture-dependent lower extremity pain, numbness/paresthesia, and weakness. The most common cause is degenerative arthritis of the spine, which results in narrowing of the spinal canal due to intervertebral disc herniation, ligamentum flavum hypertrophy, and osteophyte formation affecting the facet joints.

Answer 46

Chronically elevated venous pressure in the lower extremities can lead to incompetent venous valves and venous dilation (varicose veins). Venous congestion and tissue ischemia can result in venous stasis dermatitis.

Answer 47

refers to how well the drug distributes into tissues compared to plasma; the higher the Vd, the greater the drug distribution into the tissues. The drug concentration (mg/L) is equal to drug dose (mg) divided by Vd(L)

Answer 48

PCR testing, direct fluorescence antibody testing, or Tzanck smear. The finding of multiple painful genital ulcers and constitutional symptoms in a sexually active patient is highly suggestive of primary genital infection with herpes simplex virus.

Answer 49

The carotid sinus is a dilation of the internal carotid artery located just above the bifurcation of the common carotid artery. The carotid sinus reflex has an afferent limb that arises from the baroreceptors in the carotid sinus and travels to the vagal nucleus and medullary centers via the glossopharyngeal nerve (CN IX); the efferent limb carries parasympathetic impulses via the vagus nerve (CN X)

Answer 50

Most cases of testicular cancer are either seminomatous or nonseminomatous germ cell tumors. Nonsemiomatous germ cell tumors are composed of partially differentiated germ cells, which often retain the ability to secrete human chorionic growth hormone and alpha-fetoprotein. Serum lactate dehydrogenase, a marker of tissue injury and cell turnover, is also frequently increased.

Answer 51

an ANCA associated vasculitis that typically presents with upper (eg, purulent nasal discharge) and lower (eg, cavitary lung lesion) respiratory manifestations and renal insufficiency due to glomerulonephritis. Biopsy typically reveals a necrotizing arteritis with granulomatous inflammation (eg, epithelioid histiocytes, multinucleated giant cells) and lack of immunoglobulin/complement deposition

Answer 52

At normal plasma concentrations of glucose, the renal tubules reabsorb the entire filtered load of glucose because it is below the maximum tubular reabsorption ability (transport maximum of glucose). At higher plasma concentrations, glucose is excreted when the filtered amount exceeds the transport maximum. The serum concentration at which glucosuria begins, called the threshold of glucose, is approximately 200 mg/dL.

Answer 53

Acute tubular necrosis can be caused by renal ischemia and is characterized by oliguria, increased serum creatinine, and muddy brown casts. Ischemic injury predominantly affects the renal medulla, which has a relatively low blood supply. The proximal tubules and the thick ascending limb of the loop of Henle are the most commonly involved portions of the nephron.

Answer 54

A genital vesicular rash and a positive Tzanck smear suggest genital herpes simplex virus infection. Recurrence is common and can be mitigated with daily oral valacyclovir (preferred), acyclovir, or famciclovir

Answer 55

Cherry hemangiomas are small, red, cutaneous papules common in aging adults. They do not regress spontaneously and typically increase in number with age. Light microscopy of these lesions shows proliferation of capillaries and post capillary venules in the papillary dermis.

Answer 56

an autosomal recessive disorder in which a defective chloride channel causes impaired clearance of thick, viscous airway secretions. Patients typically develop a chronic cough, recurrent pulmonary infections, and bronchiectasis (dilated bronchial tree)

Answer 57

Matching is used in case-control studies in order to control confounding. Matching variables should always be the potential confounders of the study (eg, age, race). Cases and controls are then selected based on the matching variables so that both groups have a similar distribution in accordance with the variables.

Answer 58

Beta blockers are used in acute myocardial infarction to reduce morbidity and mortality by decreasing cardiac output and myocardial oxygen demand. Non-cardioselective beta blockers (eg, propranolol, nadolol) can trigger bronchospasm in patients with underlying asthma or COPD. Cardioselective beta blockers (eg, metoprolol) predominantly affect beta-1 receptors and are preferred in such patients.

Answer 59

a norepinephrine reuptake inhibitor that can be considered as an alternate to stimulants in the treatment of patients with ADHD who have a personal or family history of substance abuse.

Answer 60

occur in immunosuppressed patients, such as those suffering from AIDS. These tumors arise from B cells and are universally associated with EBV. They are high-grade tumors with a poor prognosis.

Answer 61

increased procoagulant factors (eg, fibrinogen), decreased anticoagulant factors (eg, protein S), and reduced fibrinolysis. These physiologic changes protect against maternal hemorrhage with delivery but increase the risk of peripartum venous thromboembolism.

Answer 62

A pudendal nerve block provides anesthesia to most of the perineum and external genitalia. It is performed by transvaginal injection of a local anesthetic medial to the ischial spine and through the sacrospinous ligament.

Answer 63

an adenylate cyclase that increases intracellular cyclic AMP, leading to neutrophil and macrophage dysfunction and tissue edema. The mechanism of action is similar to that of adenylate cyclase toxin, produced by Bordetella pertussis.

Answer 64

Atrial septal defects cause left to right atrial shunting and right sided volume overload with enlargement of the right atrium and right ventricle; left-sided volume overload does not occur as excess flow entering the left atrium cycles back into the right atrium through the septal defect. In contrast, left to right shunts distal ot the atrioventricular valves (eg, ventricular septal defect, patent ductus arteriosus) initially cause left sided volume overload

Answer 65

Can cause a transient bluish discoloration to vision. Less common ocular effects include sudden monocular vision loss due to nonarteritic anterior ischemic optic neuropathy; findings include an afferent pupillary defect, decreased visual acuity, and optic disc edema.

Answer 66

characterized by smooth muscle overgrowth of the pylorus. Gastric outlet obstruction leads to the classic presentation of nonbilious, projectile emesis and dehydration in an infant age 3-6 weeks.

Answer 67

presents with recurrent sinopulmonary and gastrointestinal infections due to the absence of CD40 ligand on CD4 T cells. Lack of interaction between CD40L and CD40 on B cells prevents the development of secondary germinal centers and impairs B cell activation and immunoglobulin class switching

Answer 68

Both perfusion and ventilation are highest in the base of the lung and lowest in the apex; however, the variability in perfusion is greater than that in ventilation. This causes the ventilation/perfusion ratio to follow the opposite gradient: it is lowest in the base and highest in the apex

Answer 69

can be directly hepatotoxic, causing acute, mild hepatic dysfunction in 10-20% patients and frank hepatitis (fever, anorexia, and nausea, sometimes progressing to hepatic failure) in a small percentage of patients

Answer 70

dsDNA - +RNA template - partially dsDNA progeny. Although it is a DNA virus, HBV uses reverse transcription to generate new viral DNA from a positive-sense RNA template

Answer 71

a sudden loss of cardiac output. Less commonly, SCD may result from cardiac arrhythmia triggered by right ventricular strain and ischemia.

Answer 72

an acute inflammation of the gallbladder in the absence of gallstones. It typically occurs in critically ill patients (eg, those with sepsis, severe burns, trauma, immunosuppression) due to gallbladder stasis and ischemia. CF: fever, RUQ pain, leukocytosis

Answer 73

Cocaine blocks the presynaptic reuptake of catecholamine neurotransmitters, including norepinephrine and dopamine. With cocaine toxicity, excessive postsynaptic stimulation by catecholamines can lead to arterial vasospasm and increased sympathetic drive, resulting in increased risk of stroke and myocardial infarction.

Answer 74

used to detect and quantify levels of mRNA in a sample. It uses reverse transcription to create a complementary DNA template that is then amplified using the standard PCR procedure. RT-PCR can be used to diagnose chronic myelogenous leukemia by identifying an mRNA transcript containing both BCR and ABL exons in affected cells.

Answer 75

its ability to infect erythrocytes of all ages. In contrast, Plasmodium ovale and Plasmodium vivax primarily infect reticulocytes, and Plasmodium malariae primarily infects old erythrocytes

Answer 76

increased CO2 retention (oxygen-induced hypercapnia), resulting in confusion and depressed consciousness. The major cause is reversal of hypoxic pulmonary vasoconstriction, which increases physiologic dead space as blood is shunted away from well-ventilated alveoli.