Uworld31 Flashcards

Question

In the forearm, the median nerve courses between?

Answer 1

the humeral and ulnar heads of the pronator teres muscle. Compression proximal to the takeoff of the palmar cutaneous branch (eg, between the heads of the pronator teres) results in sensory loss over the lateral palm and thenar eminence plus the palmar aspect of the first 3 1/2 digits.

Answer 2

The presence of Reed-Sternberg cells on lymph node biopsy is a diagnostic feature of classic Hodgkin lymphoma. RS cells have abundant cytoplasm, a multilobed nucleus or multiple nuclei, and inclusion-like nucleoli.

Answer 3

a common pattern of thyroid function markers seen in severely ill patients. It is characterized by decreased conversion of T4 to T3 in peripheral tissues. Initial findings include a low T3 level, but later, T4 and thyroid-stimulating hormone levels may also decrease. ESS may represent a mild central hypothyroid state, which functions to minimize catabolism in severe illness.

Answer 4

Diabetic mononeuropathy often involves cranial nerve III. It is caused by predominantly central ischemia, which affects the somatic nerve fibers but spares peripheral parasympathetic fibers. Symptoms include ptosis, a "down and out" gaze, and normal light and accommodation reflexes.

Answer 5

Patients with cystic fibrosis produce eccrine sweat with higher than normal concentrations of sodium and chloride. Exposure to high temperature or exercise can lead to hyponatremia and hypochloremia due to excessive sodium chloride loss through sweat; therefore, salt supplementation is recommended.

Answer 6

a well recognized complication of ulcerative colitis. Patients typically present with abdominal pain/distention, bloody diarrhea, fever, and signs of shock. Plain abdominal x-ray is the preferred diagnostic imaging study. Barium contrast studies and colonoscopy are contraindicated due to the risk of perforation.

Answer 7

Carcinoid syndrome may accompany extraintestinal metastases of gastrointestinal carcinoid tumors. Octreotide is a synthetic somatostatin analog used to control the symptoms of carcinoid syndrome.

Answer 8

Antibodies against the polysaccharide capsule of Neisseria meningitidis provide immunity against this pathogen. Quadrivalent meningococcal vaccines contain capsular polysaccharides from major serotypes (A, C, Y, and W) of N meningitidis. Serotype B vaccinations use recombinant proteins.

Answer 9

Staph aureus. Treatment of the abscess with incision and drainage and antibiotics can eliminate the local infection but does not eliminate colonization of the anterior nares and skin. Therfore, recurrent infections are common.

Answer 10

P50 refers to the partial pressure of oxygen at which hemoglobin is 50% saturated. Hemoglobins with high oxygen affinity have a decreased P50 that is represented by a leftward shift of the oxygen dissociation curve. The reduced ability to release oxygen within the peripheral tissues leads to renal hypoxia, increased erythropoietin synthesis, and compensatory eythrocytosis.

Answer 11

characterized by medullary thyroid cancer, pheochromocytoma, marfanoid habitus, and oral and intestinal mucosal neuromas.

Answer 12

the most common sleep-related breathing disorder, is characterized by recurrent obstruction of the upper airways. Relaxation of the oropharyngeal and/or soft palate musculature during sleep results in a functional collapse of the airway, producing periods of reduced (hypopnea) or absent (apnea) airflow despite continued breathing efforts.

Answer 13

statistical method commonly employed to compare the means of 2 groups of subjects.

Answer 14

Severe hypoglycemia causing impaired conciousness can be treated by a caregiver or bystander with injectable or intranasal glucagon. Glucagon rapidly corrects hypoglycemia by increasing hepatic glycogenolysis, resulting in the release of glucose from preexisting hepatic glycogen stores.

Answer 15

The clavicle is commonly fractured in children after a fall on an outstretched arm. In a distal clavicle fracture, the deltoid muscle and the weight of the arm cause inferolateral displacement of the distal fragment, whereas the sternocleidomastoid and trapezius muscles cause superomedial displacement of the proximal fragment.

Answer 16

The internal iliac artery (hypogastric artery) supplies blood to the pelvis, including the uterus via the uterine artery. Therefore, bilateral ligation of the internal iliac artery is a potential surgical management option for postpartum hemorrhage due to uterine atony.

Answer 17

characterized by intrusive experiences (flashbacks, nightmares), arousal (poor concentration, restless sleep), dissociative symptoms, and avoidance of traumatic reminders, as well as mood disturbances in response to a life-threatening trauma. Symptoms last between 3 days and 1 month.

Answer 18

A permissive hormone has no effect on a physiologic process by itself but allows another hormone to exert its maximal effect on that process. Cortisol exerts a permissive effect on catecholamines to potentiate vasoconstriction and bronchodilation; it also has a permissive effect on glucagon to increase glucose release from the liver.

Answer 19

Vertebral osteomyelitis should be suspected in patients with new or worsening back pain, fever, and recent endocarditis or bacteremia (especially Staph aureus). It should also be suspected if there are new neurologic findings and fever with or without back pain. MRI of the spine is preferred for diagnosis.

Answer 20

Photoaging is a product of excess exposure to ultraviolet A wavelengths and is characterized by epidermal atrophy with flattening of rete ridges. In addition, there is decreased collagen fibril production and increased degradation of collagen and elastin in the dermis.

Answer 21

a relatively uncommon cause of dilated cardiomyopathy that may be related to impaired function of angiogenic growth factors. Dilated cardiomyopathy involves compensatory eccentric hypertrophy, which increases ventricular compliance and also allows for temporary maintenance of cardiac output. Over time, overwhelming wall stress leads to left ventricular failure with reduced ejection fraction and symptomatic heart failure.

Answer 22

iron deficiency. Blood loss, especially occult loss from the GI tract, must be ruled out in a patient with iron def anemia/

Answer 23

usually involves autoimmune destruction of the bilateral adrenal cortex. Reduced aldosterone production leads to renal salt wasting with hypovolemia, hypotension, and hyperkalemia. The hypovolemia and reduced cortisol-induced inhibition of antidiuretic hormone lead to water retention and hyponatremia. Reduced cortisol also causes decreased circulating epinephrine with a compensatory increase in norepinephrine.

Answer 24

hemolysis, elevated liver enzymes, low platelet count. HELLP syndrome is a thrombotic microangiopathic disorder that causes microangiopathic hemolytic anemia (eg, increased indirect bilirubin levels), thrombocytopenia, and hepatocellular injury (eg, increased alanine aminotransferase). Patients may have hypertension and right upper quadrant pain with nausea/vomiting.

Answer 25

caused by circulating antibodies directed against acetylcholine receptors of the neuromuscular junction. Autoantibody binding leads to receptor degradation, producing fluctuating weakness that worsens throughout the day and most commonly affects the extraocular muscles (eg, ptosis, diplopia). Most patients have thymic abnormalities (eg, thymoma)

Answer 26

Primary oocytes are completely developed in female fetuses by the fifth month of gestation, at which point they are arrested in prophase of meiosis I. After puberty, menstrual cycle hormones stimulate the primary oocyte to resume differentiation. Prior to fertilization, secondary oocytes are arrested in metaphase of meiosis II.

Answer 27

a measure of potency of an inhaled anesthetic. It is the concentration of the anesthetic in the alveoli that renders 50% of patients unresponsive to painful stimuli (ED50). Potency is inversely proportional to the MAC; the lower the MAC, the more potent the anesthetic.

Answer 28

inhibits serotonin (5-HT3) receptors and is used primarily to treat nausea and vomiting following chemotherapy. 5-HT3 receptors are located peripherally in the presynaptic nerve terminals of the vagus nerve in the GI tract. These receptors are also present centrally in the chemoreceptor trigger zone and the solitary nucleus and tract.

Answer 29

the classic histo finding in aortic dissection, as it weakens the aortic wall and allows a small intimal tear to readily propagate. Collagen, elastin, and smooth muscle are replaced by a basophilic mucoid extracellular matrix with elastic tissue fragmentation and cystic collection of mucopolysaccharide.

Answer 30

injury of the pulmonary epithelium and/or endothelium, and occurs most often due to sepsis or pneumonia. Cytokines recruit neutrophils to the lung tissue, which cause capillary damage and leakage of protein-rich fluid into the alveoli. Later, cellular proliferation and collagen deposition occurs, and in some patients, this leads to irreversible pulmonary fibrosis.

Answer 31

most commonly results from the release of fat globules from bone marrow following a long-bone or pelvic fracture. The fat globules form inflammatory aggregates that cause microvessel obstruction and systemic inflammation leading to the triad of respiratory distress, neurologic dysfunction, and petechial rash.

Answer 32

The perineal body, which is relatively inelastic, can be damaged in an obstetric perineal laceration. The structures that form and attach to the perineal body are the bulbospongiosus, superficial transverse perineal, and external anal sphincter muscles.

Answer 33

valproate, lithium, lamotrigine, and quetiapine

Answer 34

a common and serious complication of chronic hemolytic anemia and frequent blood transfusions. Accumulation of yellow-brown hemosiderin pigment is the cardinal histo finding. Chelation therapy is indicated to reduce parenchymal iron deposition.

Answer 35

Ecchymoses frequently indicate a deep hemorrhage (hematoma) due to bony fracture, ligamentous rupture, or muscular injury. They do not blanch under pressure as the red blood cells are not contained within the vasculature. Ecchymoses often pass through an evolution of color change (blue to red to brown, green and yellow), which can be used to estimate the age of injury.

Answer 36

release of tissue factor, a procoagulant that activates the coagulation cascade, from the damaged decidua into the maternal circulation. DIC classically presents with thrombocytopenia and bleeding from mucosal surfaces (eg, gums) and intravenous line sites.

Answer 37

The duodenal brush border enzyme enteropeptidase activates trypsin from its inactive precursor, trypsinogen. Trypsin degrades complex polypeptides to dipeptides, tripeptides, and amino acids while activated other pancreatic enzymes. Enteropeptidase deficiency impairs both protein and fat absorption, leading to diarrhea, failure to thrive, and hypoproteinemia.

Answer 38

Traumatic injury to the eye, an area of the body that has inherent immune privilege, can lead to the release of previously sequestered antigens that T cells recognize as foreign. This can lead to subsequent inflammation and blindness in both the injured and uninjured eye.

Answer 39

opportunistic infection with cytomegalovirus, an enveloped virus that contains a double-stranded DNA genome.

Answer 40

a group of rare hereditary disorders characterized by defective collagen synthesis. It can be caused by procollagen peptidase deficiency, which results in impaired cleavage of terminal propeptides in the extracellular space. Patients often have joint laxity, hyperextensible skin, and tissue fragility due to the formation of soluble collagen that does not properly crosslink.

Answer 41

The short gastric veins drain blood from the gastric fundus into the splenic vein. Pancreatic inflammation (eg, pancreatitis, pancreatic cancer) can cause a blood clot within the splenic vein, which can increase pressure in the short gastric veins and lead to gastric varices only in the fundus

Answer 42

In the fibrinolytic pathway, tissue plasminogen activator (tPA) converts plasminogen to plasmin, which then breaks down fibrin clot. The adminstration of a tPA analogue (eg, alteplase, tenecteplase, streptokinase) triggers fibronlysis and can restore myocardial perfusion in patients with ST-elevation myocardial infarction who cannot undergo timely percutaneous coronary intervention.

Answer 43

The anterior cerebral arteries supply the medial portions of the 2 hemispheres (frontal and parietal lobes). Occlusion can cause contralateral motor and sensory deficits of the lower extremities, behavioral changes, and urinary incontinence.

Answer 44

R5 strains (macrophage-tropic) of HIV attach to the host CD4 receptor and CCR5 chemokine coreceptor; CCR5 inhibitors such as maraviroc can be used in the treatment of R5 virus. X4 strains (T lymphotropic) of HIV bind to the CD4 receptor and CXCR4 chemokine receptor; X4 virus cannot be treated with CCR5 inhibitors.

Answer 45

Multiple origins of replication make eukaryotic DNA replication quick and effective despite the large size and complexity of the genome compared to that of prokaryotic organisms.

Answer 46

Protamine sulfate binds to heparin, causing chemical inactivation.

Answer 47

Vitamin K and fresh frozen plasma

Answer 48

Antiviral drugs currently recommended for the treatment of primary genital herpes include the nucleoside analogs (eg, acyclovir). These are incorporated into newly replicating viral DNA and ultimately terminate viral DNA chain synthesis

Answer 49

Cell mediated immunity is the primary mechanism underlying giant cell arteritis. The production of cytokines, in particular IL-6, is an important driver of this process and closely correlates with the severity of symptoms

Answer 50

Vitamin A can be beneficial in the treatment of measles infection by reducing comorbidities (eg, ocular complications, diarrhea, pneumonia), recovery time, and length of hospital stay.

Answer 51

Often begins abruptly following severe medical (eg, myocardial infarction) or emotional stressors. The symptoms are often situational, with normal erections at night or during masturbation but impaired with a partner. Libido is often normal.

Answer 52

Atrial fibrillation is associated with increased risk of systemic thromboembolism. The left atrial appendage is the most common site of thrombus formation in atrial fibrillation.

Answer 53

a Th2 cell-mediated disorder leading to eosinophilic infiltration of the esophageal mucosa. It occurs most commonly in males individuals with a history of atopic conditions and typically presents with solid food dysphagia, reflux, and occasionally food impaction. Classic endoscopic findings include stacked, ring like indentations; linear furrowing, and scattered, small whitish papules (ie, eosinophilic microabscesses)

Answer 54

Finasteride acts on epithelium and alpha 1 blockers act on smooth muscles of prostate and bladder base.

Answer 55

Burkitt lymphoma, an aggressive B cell malignancy, can be associated with Epstein-Barr virus infection. It typically presents as a rapidly growing mass (eg, abdomen). Histopathology shows sheets of uniform, medium sized lymphoid cells with numerous mitotic figure (ie, high proliferation rate) and apoptotic bodies.

Answer 56

Uncomplicated parapneumonic effusions result from movement of sterile exudate into the pleural space, whereas complicated parapneumonic effusions involve inflammatory disruption of the visceral pleural membrane with bacterial translocation into the pleural space.

Answer 57

A benign glomus tumor (glomangioma) can produce a very tender, small (a few millimeters in diameter), red-blue lesion under the nail bed. This type of tumor originates from the modified smooth muscle cells that control the thermoregulatory functions of dermal glomus bodies.

Answer 58

chronic CO2 retention leading to compensated respiratory acidosis (increase PaCO2 with increase HCO3-) producing a low-normal pH, often accompanied by hypoxemia

Answer 59

Increased aspartate aminotransferase and alanine aminotransferase are indicators of hepatocellular damage, and increased alkaline phosphatase and gamma-glutamyl transpeptidase indicate biliary injury. Serum albumin levels, bilirubin levels, and prothrombin time are reflective of liver function and are of greatest prognostic significance in patients with cirrhosis.

Answer 60

TNF-a is thought to mediate paraneoplastic cachexia in humans by suppressing appetite and increasing basal metabolic rate.

Answer 61

with signs/symptoms of bone marrow failure (eg, bleeding due to thrombocytopenia). Immunophenotyping by flow cytometry establishes the specific subtype; B-lymphoblastic leukemia shows expression of deoxynucleotidyl transferase (TdT) (marker expressed in lymphoblasts) and B cell markers (eg, CD10, CD19)

Answer 62

a selective alpha-1 agonist with no effect on alpha-2 or beta receptors. It causes peripheral vasoconstriction that increases systemic vascular resistance and blood pressure. It has no direct effect on the heart but stimulates a reflex-mediated decrease in heart rate and myocardial contractility

Answer 63

a tumor suppressor gene that control cell division and apoptosis. It is inactivated in many tumors.

Answer 64

characterized by inadequate surfactant production, resulting in increased alveolar surface tension and decreased alveolar compliance. Diffuse alveolar collapse (atelectasis) is seen on chest x-ray as ground-glass opacities with air bronchograms.

Answer 65

the probability of rejecting a null hypothesis when it is truly false. It is typically set at 80% and depends on sample size and difference between outcomes.

Answer 66

Atherosclerosis is a pathophysiologic process involving endothelial cell dysfunction, and it develops most rapidly in areas with bends and branch points that encourage turbulent blood flow. The lower abdominal aorta and coronary arteries are the vascular beds most susceptible to atherosclerosis; they tend to develop atherosclerosis earliest in life and have the highest overall atherosclerotic burden.

Answer 67

chorioretinitis

Answer 68

Portal hypertension, as seen in alcoholic liver disease, produces splenomegaly by causing congestion of blood within the spleen, which produces expansion of the red pulp.

Answer 69

Acute management of variceal hemorrhage requires rapid lowering of portal pressure. Somatostatin and octreotide (a long acting somatostatin analog) inhibit the release of hormones that induce splanchnic vasodilation, indirectly causing splanchnic vasoconstriction and reduced portal blood flow.

Answer 70

Upper motor neuron damage leads to spastic paralysis, hyperreflexia, and an upgoing plantar reflex (Babinski sign) due to loss of descending inhibition over lower motor neurons in the anterior horn. Conversely, lower motor neuron lesions cause flaccid paralysis, hypotonia, hyporeflexia, muscle atrophy, and fasciculations.

Answer 71

the most common type of pericarditis and is characterized by pericardial inflammation with serous, fibrin-containing exudate in the pericardial space. Pleuritic chest pain and a triphasic friction rub are frequently seen. Common causes include viral infection, myocardial infarction, uremia, and rheumatologic disease (eg, systemic lupus erythematosus, rheumatoid arthritis)

Answer 72

osteoporosis primarily involving the cortical bone of the appendicular skeleton. The cortical thinning appears radiologically as subperiosteal erosions. More advanced disease can present as osteitis fibrosa cystica (ie, granular decalcification of the skull, osteolytic cysts, and brown tumors)

Answer 73

Ostructive sleep apnea is due to upper airway muscle relaxation leading to repetitive pharyngeal collapse. The degree of collapse is highest when muscle tone is globally inhibited during rapid eye movement sleep. Collapse is also greatest in the supine position due to the effect of gravity on the upper airway structures.

Answer 74

Aortic regurgitation causes a rapid fall in aortic pressure during diastole with an increase in left ventricular end-diastolic volume and a compensatory increase in stroke volume. These hemodynamic changes create characteristic pressure changes, including reduced aortic diastolic pressure, increased aortic systolic pressure, and increased left ventricular diastolic and systolic pressures.

Answer 75

Intussusception, which presents with colicky abdominal pain, is characterized by telescoping of one intestinal segment into an adjacent one, most commonly at the ileocecal junction. Pathophysiology usually involves hypertrophy of intestinal lymphoid follicles (Peyer patches), which can act as lead points of the invaginated bowel.

Answer 76

the number of patients who need to be treated with a specific treatment to avoid an additional negative event. NNT is the inverse of the absolute risk reduction. NNT= 1/ARR ARR= (Risk control - Risk txt)