USMLE Exam 1

This is a timed quiz. You will be given 60 seconds per question. Are you ready?

60
0%

Choose the correct answer

Correct! Wrong!

Because creatinine is freely filtered by the glomerulus, but not secreted or reabsorbed to a significant extent, the renal clearance of creatinine is approximately equal to the glomerular filtration rate (GFR). In fact, creatinine clearance is commonly used to assess renal function in the clinical setting. When a kidney is removed, the total glomerular filtration rate decreases because 50% of the nephrons have been removed, which causes the creatinine clearance to decrease. In turn, the plasma creatinine concentration increases until the rate of creatinine excretion by the kidneys is equal to the rate of creatinine production by the body. Recall that creatinine excretion = GFR x plasma creatinine concentration. Therefore, creatinine excretion is normal when GFR is decreased following removal of a kidney because the plasma concentration of creatinine is elevated. Creatinine is a waste product of metabolism. Creatinine production is directly related to the muscle mass of an individual, but is independent of renal function. The daily excretion of sodium is unaffected by the removal of a kidney. The amount of sodium excreted each day by the remaining kidney exactly matches the amount of sodium entering the body in the diet.

Choose the correct answer

Correct! Wrong!

The most probable etiology of bacterial endocarditis involving the tricuspid valve is illicit IV drug use, which can introduce skin organisms into the venous system that then attack the tricuspid valve. Staphylococcus aureus accounts for between 60% and 90% of cases of endocarditis in IV drug users. The endocarditis associated with congenital heart disease typically involves either damaged valves or atrial or ventricular septal defects. The tricuspid valve is not particularly vulnerable. Rheumatic fever most commonly damages the mitral and aortic valves, and tricuspid damage is usually less severe and seen only when the mitral and aortic valves are heavily involved. Consequently, secondary bacterial endocarditis involving only the tricuspid valve in a patient with history of rheumatic fever would be unusual. Rheumatoid arthritis is not associated with bacterial endocarditis. Systemic lupus erythematosus can produce small, aseptic vegetations on valves, but is not associated with bacterial endocarditis

Choose the correct answer

Correct! Wrong!

This statement from the father would reflect his understanding of the egocentric nature of school-aged children. That is, the child is assuming that he is responsible for the divorce between his parents. The anger and withdrawal reflect the child’s frustration with the situation, but the tears and apology suggest the child’s fear and assumed responsibility for the breakup. “Big boys don’t cry” is a demeaning and belittling statement. “I’ll see you in 2 weeks”ignores the child’s felt responsibility for the divorce. “You’re the man of the house now” places too much responsibility on a 7-year-old child. “Your mother was too hard to live with” places all the blame and responsibility for the divorce on the parent, with whom the boy lives on a daily basis. It ignores the reality that divorce is usually due to difficulties that both parents have with each other.

Choose the correct answer

Correct! Wrong!

The infant has Hirschsprung disease, which is due to an absence of ganglion cells in the wall of the colon. Neural crest cells contribute to the formation of many adult structures. Among these are all of the postganglionic neurons of the autonomic nervous system and the sensory neurons of the peripheral nervous system. Ectoderm forms the epidermis of the skin and the parenchymal cells of glands associated with the skin, such as the sweat glands, sebaceous glands, and mammary glands. Endoderm forms the epithelial lining of the gut tube and the parenchymal cells of glands associated with the gut tube, such as the liver and pancreas. Neural ectoderm forms the CNS, the somatic motor neurons of the peripheral nervous system, and the preganglionic neurons of the autonomic nervous system. Splanchnic mesoderm forms the visceral peritoneum, the visceral pleura, the visceral pericardium, and the stroma and muscle of the wall of the gut, among other structures.

Choose the correct answer

Correct! Wrong!

All the organisms listed are protozoa. There are two intestinal protozoa specifically associated with AIDS that can cause transient diarrhea in immunocompetent individuals but can cause debilitating, and potentially life-threatening, chronic diarrhea in AIDS patients. These organisms are Isospora belli, treated with trimethoprim-sulfamethoxazole or other folate antagonists) and Cryptosporidium parvum (no treatment currently available). Diphyllobothrium latum is the fish tapeworm and occasionally causes diarrhea. Entamoeba histolytica and Giardia lamblia are both causes of diarrhea, but they are not specifically associated with AIDS. Microsporidia are a protozoan cause of diarrhea but produce spores rather than oocysts.

Choose the correct answer

Correct! Wrong!

There are three facts that are necessary to answer this question: what disease the patient is suffering from, what pharmacological properties can trigger an attack, and what drug has these pharmacological properties. The patient described is suffering from an attack of acute or narrow angle glaucoma. These attacks can be precipitated by drugs with anticholinergic actions because muscarinic receptors on the pupillary constrictor muscle of the iris are blocked. This causes pupillary dilation, which further “narrows” the angle in the anterior chamber of the eye. Amitriptyline is a tricyclic antidepressant with significant anticholinergic side effects. Cimetidine is an H2 antagonist that reduces gastric acid release. Its trade name is Tagamet and it is now available over the counter. It has no significant anticholinergic side effects. Diazepam is a benzodiazepine. Its trade name is Valium and it has no significant anticholinergic side effects. Malathion is an organophosphorus cholinesterase inhibitor that is used as an insecticide. This agent would increase levels of acetylcholine, thereby widening the angle. Propranolol is a non-selective, beta-adrenergic antagonist. If anything, it would help to prevent an attack by blocking beta-receptors on the ciliary body, thereby diminishing aqueous humor production.

Choose the correct answer

Correct! Wrong!

The patient has a ventricular tachycardia as indicated by the electrocardiogram: the appearance of a wide-complex ventricular tachycardia with a rate of 126 beats per minute. Propranolol is a Type II antiarrhythmic agent that acts by decreasing SA node automaticity, increasing AV nodal refractoriness, and decreasing AV nodal conduction velocity. Propranolol is indicated for the treatment of ventricular tachycardias, supraventricular arrhythmias, and for slowing the ventricular rate during atrial fibrillation and atrial flutter. Amiodarone is a Type III antiarrhythmic that acts by prolonging the action potential duration in tissue with fast-response action potentials. Amiodarone is indicated for treatment of refractory ventricular arrhythmias that are unresponsive to other antiarrhythmics. Disopyramide is a Type IA antiarrhythmic that reduces the maximal velocity of phase 0 depolarization by blocking the inward sodium current in tissue with fast-response action potentials. It also increases the action potential duration. Disopyramide is indicated for the treatment of atrial and ventricular extrasystoles and atrial and ventricular tachyarrhythmias. Lidocaine is a Type IA antiarrhythmic that reduces the maximal velocity of phase 0 depolarization by blocking the inward sodium current in tissue with fast-response action potentials. Lidocaine is indicated for the treatment of atrial and ventricular extrasystoles, and atrial and ventricular tachyarrhythmias. Verapamil, a Type IV antiarrhythmic agent, blocks calcium channels, thereby decreasing conduction velocity and increasing refractoriness in tissue with slow-response action potentials. Verapamil is indicated for the treatment of atrial fibrillation and flutter as well as other atrial tachycardias.

Choose the correct answer

Correct! Wrong!

The child described is exhibiting the features of Angelman (happy puppet) syndrome. This disorder is generally caused by a deletion of band q12 in the maternal copy of chromosome 15, i.e., [(del (15)(q11q13)]. A similar deletion in the paternal chromosome 15 produces Prader-Willi syndrome. The disparate expression of the effects of deletions in the paternal vs. the maternal chromosomes, called genomic imprinting, implies that the same genetic loci are expressed quite differently in maternal and paternal chromosomes. Angelman syndrome can also occur if uniparental disomy occurs for chromosome 15, such that the embryo receives two copies of the maternal chromosome 15 without the paternal chromosome 15 to “balance” the maternal contribution. Confined placental mosaicism is due to a mutation occurring within trophoblast or extraembryonic precursor cells of the inner cell mass and is an important cause of intrauterine growth retardation. Expansion of a trinucleotide repeat is associated with Fragile X syndrome and Huntington disease. Point mutation in autosomes has not been associated with Angelman syndrome. Random inactivation of the X chromosome occurs normally, as postulated in the Lyon hypothesis.

Choose the correct answer

Correct! Wrong!

he question stem describes the typical presentation of measles (rubeola), which is caused by a Morbillivirus, an RNA virus belonging to the Paramyxovirus family. Koplik spots, which are pathognomonic for measles, are small, bluish-white spots on the buccal mucosa in the early stages of the disease. These lesions appear just before the onset of the characteristic rash (which can also involve the extremities) and fade as the rash develops. Leukoplakia is a premalignant condition characterized by adherent whitish patches on the gingiva and other sites in the oral cavity. Cold sores of the lips are due to infection with Herpes viruses. Candida infection (thrush) produces curdy white material loosely attached to an erythematous base. Aphthous ulcers are large shallow ulcers of the oral mucosa, commonly known as canker sores.

Choose the correct answer

Correct! Wrong!

The patient has developed bacteremia; the description of the causative agent is consistent with a staphylococcal organism (catalase positive, gram-positive cocci that grow on mannitol salt agar). The organism is most likely Staphylococcus epidermidis as it was not able to ferment mannitol and was not hemolytic. Both of these characteristics tend to rule out Staphylococcus aureus. Two other tests that are commonly used are coagulase production and excretion of DNAse from colonies. S. aureus is positive in both tests, S. epidermidis is negative. Enterococcus faecalis might grow on the mannitol salt agar as it is relatively haloduric but these organisms are catalase negative. The enterococci are extremely variable in hemolytic ability so this characteristic is not useful in species identification. Both streptococcal organisms are catalase negative and beta-hemolytic on sheep blood agar plates. Also, neither would grow on the mannitol salt agar. Streptococcus pyogenes is sensitive to growth inhibition by bacitracin, whereas Streptococcus agalactiae (group B streptococci) is not.

Choose the correct answer

Correct! Wrong!

Patients with selective IgA deficiency may have circulating antibodies to IgA. Fatal anaphylaxis may ensue if they are transfused with blood products with serum containing IgA, although many patients with selective IgA deficiency are asymptomatic and never diagnosed. Symptomatic patients may have recurrent sinopulmonary infections and diarrhea, as well as an increased incidence of autoimmune and allergic diseases. AIDS predisposes for infections and neoplasms, but not anaphylaxis. C1 esterase inhibitor deficiency is an autosomal dominant disease characterized by recurrent attacks of colic and episodes of laryngeal edema, without pruritus or urticarial lesions. This disorder is also known as hereditary angioedema. DiGeorge syndrome is characterized by thymic aplasia and, sometimes, hypoparathyroidism. The disorder is due to abnormal development of the third and fourth pharyngeal arches. Wiskott-Aldrich syndrome is a form of immunodeficiency associated with thrombocytopenia and eczema.

Choose the correct answer

Correct! Wrong!

The tumors are serous papillary cystadenocarcinomas of the ovaries. These tumors express CA-125 and are apparently derived from the surface epithelium of the ovaries. Alpha-fetoprotein is not produced by this type of ovarian tumor but can be produced by testicular tumors and, less commonly, by ovarian tumors with a yolk sac tumor component. Bombesin is a marker for neuroblastoma, small cell carcinoma, gastric carcinoma, and pancreatic carcinoma. PSA is a marker for prostatic carcinoma. S-100 is a marker for melanoma, neural tumors, and astrocytomas.

Choose the correct answer

Correct! Wrong!

The anterior continuation of the cavernous sinus, the superior ophthalmic vein, passes through the superior orbital fissure to enter the orbit. Veins of the face communicate with the superior ophthalmic vein. Because of the absence of valves in emissary veins, venous flow may occur in either direction. Cutaneous infections may be carried into the cavernous sinus and result in a cavernous sinus infection, which may lead to an infected cavernous sinus thrombosis. The cavernous sinus is lateral to the pituitary gland and contains portions of cranial nerves III, IV, V1, V2 and VI, and the internal carotid artery. The occipital sinus is at the base of the falx cerebelli in the posterior cranial fossa. It drains into the confluence of sinuses. The sigmoid sinus is the anterior continuation of the transverse sinus in the middle cranial fossa. The sigmoid sinus passes through the jugular foramen and drains into the internal jugular vein. The straight sinus is at the intersection of the falx cerebri and the falx cerebelli in the posterior cranial fossa. The straight sinus connects the inferior sagittal sinus with the confluence of sinuses. The superior petrosal sinus is at the apex of the petrous portion of the temporal bone and is a posterior continuation of the cavernous sinus. The superior petrosal sinus connects the cavernous sinus with the sigmoid sinus.

Choose the correct answer

Correct! Wrong!

Achalasia is an acquired esophageal motility disorder that is characterized by loss of enteric inhibitory neurons. The lower esophageal sphincter may exhibit increased tone in between swallows and fail to relax normally with a swallow. Peristalsis in the esophageal body is also abnormal. A swallow may not induce any peristalsis in the esophageal body or may produce simultaneous contractions along its entire length. The esophageal body distal to the diaphragm is relaxed in between swallows. The intraesophageal pressure at this point reflects the intra-abdominal pressure, which is slightly positive (5 mm Hg). During inspiration, the pressure inside the distal esophagus rises along with the intra-abdominal pressure; during expiration this pressure falls. The pressure in the esophageal body proximal to the diaphragm reflects the intrathoracic pressure. It is slightly negative at the end of inspiration and slightly positive at the end of expiration. Since the mouth and pharynx are open to the atmosphere, in between swallows, the pressure within the pharynx is atmospheric (0 mm Hg). The pressure rises abruptly to a maximum of 100 mm Hg at the start of a swallow and returns to baseline within 0.5 seconds. At rest, the pressure in the upper esophageal sphincter can be as high as 60 mm Hg. It is maintained by the normal elasticity of the sphincteric structures, as well as by active contraction of the cricopharyngeal muscle, which composes most of the sphincter. Shortly after the pharyngeal muscles contract during a swallow, the upper esophageal sphincter relaxes as the tonic neural input to the cricopharyngeal muscle (skeletal muscle) is inhibited as part of the swallowing program. Function of this sphincter is unaffected by achalasia.

Choose the correct answer

Correct! Wrong!

The superior pancreaticoduodenal artery is a branch of the gastroduodenal artery, which is a branch of the common hepatic artery, itself a branch of the celiac trunk. The inferior pancreaticoduodenal artery is a branch of the superior mesenteric artery. Occlusion of the celiac trunk would allow blood from the superior mesenteric artery to reach the branches of the celiac trunk via the connections between the superior and inferior pancreaticoduodenal arteries. Both the left and right gastric arteries receive their blood from the celiac trunk. The left gastric artery is a direct branch of the celiac trunk. The right gastric artery is usually a branch of the proper hepatic artery, which is a branch of the common hepatic artery (a branch of the celiac trunk). Both the left and right gastroepiploic arteries receive their blood supply from the celiac trunk. The left gastroepiploic artery is a branch of the splenic artery, which is a branch of the celiac trunk. The right gastroepiploic artery is a branch of the gastroduodenal artery, which is a branch of the common hepatic artery (a branch of the celiac trunk). The proper hepatic and gastroduodenal arteries are branches of the common hepatic artery, which is a branch of the celiac trunk. The right colic and middle colic arteries are both branches of the superior mesenteric artery.

Choose the correct answer

Correct! Wrong!

Malignant mixed mullerian tumor is a tumor with two components, stromal and epithelial (endometrial glands), both of which are malignant. This is a rare and highly aggressive tumor that has a 25% 5-year survival rate. It usually affects older patients and presents with postmenopausal bleeding. The stromal component can contain metaplastic components such as cartilage and bone. Interestingly, usually only the epithelial component metastasizes. Endolymphatic stromal myosis is a type of endometrial stromal tumor of intermediate malignancy. It appears as small pieces of stroma between myometrial bundles that infiltrate lymph channels. Patients may have pain or bleeding, or may be asymptomatic. Recurrences happen late in the course of the disease (years) in 50% of patients, and metastasis occurs in 15%. There is no epithelial component, so this is an incorrect choice. Endometrial carcinoma is a malignancy of the epithelial glandular component of the endometrium. Abnormal bleeding is the usual presentation. High estrogen states cause this tissue to proliferate. There is no stromal component of this tumor, so this is an incorrect choice. Endometrial stromal sarcoma is a true sarcoma arising from the endometrial stroma that infiltrates the myometrium and invades vessels. There is no epithelial component. Leiomyosarcoma is a true sarcoma arising from the uterine smooth muscle. It commonly has satellite lesions within the uterus. Leiomyosarcomas usually recur after removal; survival is greater with well-differentiated lesions. Poorly differentiated lesions have a 10% to 15% 5-year survival rate. Distant metastasis is via blood vessels. There is no epithelial component.

Choose the correct answer

Correct! Wrong!

Because the right main bronchus is wider and more vertical than the left, foreign objects are more likely to be aspirated into the right main bronchus. The superior segmental bronchus of the lower lobar bronchus is the only segmental bronchus that exits from the posterior wall of the lobar bronchi. Therefore, if a patient is supine at the time of aspiration, the object is most likely to enter the superior segmental bronchus of the lower lobe. None of the segmental bronchi of the left lung are likely to receive the object because the object is less likely to enter the left main bronchus. The apical segment of the right upper lobe is not likely to receive the foreign object because of the sharp angle that the upper lobar bronchus makes with the right main bronchus, and the sharp angle that the apical segmental bronchus makes with the lobar bronchus. The medial segmental bronchus of the right middle lobe arises from the anterior wall of the right middle lobar bronchus. Therefore, when the patient is supine, the effect of gravity will tend to prevent the object from entering this segmental bronchus.

Choose the correct answer

Correct! Wrong!

The patient has prostate cancer causing osteoblastic bone lesions. Osteoblastic cells respond to metastatic prostate carcinoma by forming bone (osteoid) and secreting alkaline phosphatase, which is thought to either initiate or facilitate mineralization. Prostatic acid phosphatase and prostatic-specific antigen are not correct because they do not answer the question being asked. The question asks for bone metabolites related to the patients skeletal metastasis. These two markers are synthesized by the tumor and would most likely be elevated in this case; however, they are elevated because of the prostatic cancer, independent from the bony metastasis. Tartrate-resistant acid phosphatase and urinary hydroxyproline are metabolic markers of osteoclastic (not osteoblastic) cell activity. Lytic tumor metastasis (lung, kidney, gastrointestinal tract, melanoma) would be associated with increased levels of these markers. Tartrate-resistant acid phosphatase is secreted by the osteoclast during bone resorption. Hydroxyproline is associated with collagen breakdown, and increased levels are excreted in the urine.

Choose the correct answer

Correct! Wrong!

The brachial artery is immediately medial to the tendon of the biceps brachii at the elbow. As the artery enters the forearm, it is covered by the bicipital aponeurosis, a broadening of the biceps tendon. The musculocutaneous nerve does not cross the elbow. The musculocutaneous nerve gives off all of its muscular branches to muscles in the arm. The remainder of the nerve is then renamed the lateral cutaneous nerve of the forearm, which passes the elbow lateral to the tendon of the biceps. The profunda brachii artery arises from the brachial artery in the proximal part of the arm. It accompanies the radial artery in the musculospiral groove and then divides into the radial collateral artery and middle collateral artery, which cross the elbow lateral to the tendon of the biceps. The radial nerve lies within the musculospiral groove along the back of the humerus, then passes between the brachioradialis muscle and the brachialis muscle at the elbow, lateral to the tendon of the biceps. The ulnar nerve crosses the elbow posterior to the medial epicondyle of the humerus. It then passes between the two heads of the flexor carpi ulnaris and courses through the forearm deep to this muscle.

Choose the correct answer

Correct! Wrong!

The husband is suffering from Kartagener syndrome, an autosomal recessive disorder characterized by infertility, situs inversus, chronic sinusitis, and bronchiectasis. The underlying cause of these varied manifestations is a defect in the dynein arms, which are spokes of microtubule doublets of cilia in the airways and the reproductive tract. Since sperm motility is dependent on the functioning of cilia, infertility frequently accompanies this disorder. Situs inversus occurs because ciliary function is necessary for cell migration during embryonic development. Azoospermia is not a feature of Kartagener syndrome, as sperm production or survival is not affected in this disorder. Germinal cell aplasia, also known as Sertoli-only syndrome, is characterized by oligospermia or azoospermia. Isolated gonadotropin deficiency is characterized by delayed or incomplete pubertal maturation. Varicocele results in an increased testicular temperature, decreasing the count of normal, viable sperm.

Choose the correct answer

Correct! Wrong!

The infant probably has esophageal atresia, which is typically caused by posterior deviation of the tracheoesophageal septum. Attempts at feeding cause fluid to spill into the trachea, and secondarily cause aspiration pneumonia. Emergent surgical correction is usually required. Bronchogenic cysts are centrally located cysts that are often asymptomatic and may be associated with cysts of other organs. Congenital pulmonary cysts are often multiple and located in the lung periphery without connection to the bronchi; they are vulnerable to infection and rupture complicated by pneumothorax and/or hemoptysis. Pulmonary immaturity produces progressive difficulty in breathing beginning in the first few hours of life. Pulmonary sequestration represents extrapulmonary lung tissue supplied by systemic blood vessels rather than by pulmonary arteries.

Choose the correct answer

Correct! Wrong!

Bacillus cereus produces a self-limited diarrhea due to ingestion of the preformed enterotoxin in contaminated fried rice and seafood. The incubation period is typically around 4 hours. The degree of vomiting is greater than the diarrhea. B. cereus is also associated with keratitis, producing a corneal ring abscess. Clostridium botulinum produces a neurotoxin that blocks the release of acetylcholine, resulting in a symmetric descending paralysis that may lead to respiratory complications causing death. Symptoms include blurred vision, photophobia, dysphagia, nausea, vomiting, and dysphonia. Most cases are associated with the ingestion of contaminated home-canned food. Clostridium perfringens produces a severe diarrhea with abdominal pain and cramping (sometimes called “church picnic” diarrhea). The incubation period is 8-24 hours after ingesting contaminated meat, meat products, or poultry. The meats have usually been cooked, allowed to cool, and then warmed, which causes germination of the clostridial spores. EHEC, enterohemorrhagic Escherichia coli, produces a bloody, noninvasive diarrhea due to the ingestion of verotoxin found in undercooked hamburger at fast food restaurants. The 0157:H7 serotype typically produces this syndrome. Some patients develop a life-threatening complication called hemolytic-uremic syndrome. Staphylococcus aureus produces a self-limited food poisoning syndrome with nausea, vomiting, and abdominal pain followed by diarrhea beginning 1-6 hours after ingestion of the enterotoxin. The organism is found in foods such as potato salad, custard, milk shakes, and mayonnaise. Vibrio cholerae typically produces a watery, nonbloody diarrhea with flecks of mucus (rice-water stools). Abdominal pain is not a feature. Massive fluid loss and electrolyte imbalance are complications. In the U.S., cases of cholera (El Tor 01 strain) are associated with the Gulf coast and ingestion of poorly cooked or poorly stored crabs, shrimp, or oysters. A strain of V. cholerae, called non-01, is also found along the Gulf coast. Patients who ingest contaminated shellfish experience fever, copious watery diarrhea, and abdominal cramps within 48 hours after eating.

Choose the correct answer

Correct! Wrong!

In utero differentiation of the Wolffian ducts into the normal male phenotypic internal reproductive tract requires testosterone, but not dihydrotestosterone. On the other hand, differentiation of the indifferent external genital slit into the penis, prostate, and scrotum does require dihydrotestosterone. A congenital absence of 5α-reductase in these tissues will result in feminization. If left untreated, the affected individuals are generally phenotypic females until puberty, at which time increased amounts of testosterone result in virilization ("penis-at-twelve" syndrome). If discovered early, a male gender assignment can be supported with administration of dihydrotestosterone to increase penis size. If discovered after infancy, a female gender assignment can be supported with estrogen substitution therapy and prophylactic orchiectomy. With complete androgen resistance, the external genitalia are feminized, but neither the male-type nor the female-type internal tracts develop. In the absence of the androgen receptor, the Wolffian ducts will degenerate. The Müllerian ducts will also degenerate because of the normal effect of testicular Müllerian regression factor. With 17a-hydroxylase deficiency, the testes cannot synthesize testosterone, resulting in feminization of the external genitalia and degeneration of the Wolffian ducts. Normal secretion of Müllerian regression factor should also cause the degeneration of the Müllerian ducts. Because of the excessive secretion of deoxycorticosterone by the adrenal cortex, these individuals are usually hypertensive. The Sertoli-only syndrome refers to the situation in which only the Sertoli cells of the seminiferous tubules are present (germinal cell aplasia). Spermatogenesis is absent in these individuals, who also show increased plasma levels of FSH because of decreased Sertoli cell secretion of inhibin. They may exhibit both male-type and female-type internal tracts because of the absence of Müllerian regression factor. The Leydig cells, however, have normal function and result in normal secretion of testosterone, so that both male-type internal tracts and external genitalia develop. Testicular dysgenesis results in poor in utero development of the testes with concomitantly decreased secretion of testosterone and Müllerian regression factor. The Wolffian duct structures may degenerate, and the external genitalia may be feminized. Female-type internal tracts may develop because of the decreased secretion of Müllerian regression factor.

Choose the correct answer

Correct! Wrong!

Von Gierke disease is a glycogen storage disease caused by a deficiency of glucose-6-phosphatase. It typically presents with neonatal hypoglycemia, hyperlipidemia, lactic acidosis, and ketosis. Failure to thrive is common in early life; convulsions may occur because of profound hypoglycemia. The glycogen accumulation in von Gierke disease occurs primarily in the liver and kidneys, accounting for the enlargement of these organs. Gout may develop later because of the derangement of glucose metabolism. Even if you do not remember all the details of the presentation of these genetic diseases, you should be able to narrow the choices: Gaucher disease and Niemann-Pick disease are lipid storage diseases and would not be expected to produce hypoglycemia. The other diseases are glycogen storage diseases, but both McArdle and Pompe diseases affect muscle rather than liver and would not be expected to produce profound hypoglycemia, since the liver is the major source for blood glucose.

Choose the correct answer

Correct! Wrong!

Pasteurella multocida is a gram-negative rod that is normal flora of the oral cavity of dogs and cats. It often causes a local abscess following introduction under the skin by an animal bite. Most cases occur in children who are injured while playing with a pet. Bartonella henselae is a very small, gram-negative bacterium that is closely related to the rickettsia, although it is able to grow on lifeless media. It is the cause of cat-scratch disease (a local, chronic lymphadenitis most commonly seen in children) and bacillary angiomatosis (seen particularly in AIDS patients). In this latter patient population, the organism causes proliferation of blood and lymphatic vessels causing a characteristic “mulberry” lesion in the skin and subcutaneous tissues of the afflicted individual. Brucella canis is a gram-negative rod that is a zoonotic agent. Its normal host is the dog. When it gains access to humans, however, it causes an undulating febrile disease with malaise, lymphadenopathy and hepatosplenomegaly. The normal route of exposure is via ingestion of the organism. Clostridium tetani is a gram-positive spore-forming anaerobic rod. It causes tetanus [a spastic paralysis caused by tetanospasmin, which blocks the release of the inhibitory neurotransmitters glycine and gamma-aminobutyric acid (GABA)]. There may be no lesion at the site of inoculation, and exudation would be extremely rare. Toxocara canis, a common intestinal parasite of dogs, is a metazoan parasite that causes visceral larva migrans. Young children are most likely to be affected, as they are most likely to ingest soil contaminated with eggs of the parasite.

Choose the correct answer

Correct! Wrong!

Several gastrointestinal diseases are associated with rheumatologic complaints. The most frequent of these are the chronic inflammatory bowel diseases, ulcerative colitis, and Crohn disease, which can be associated with sacroiliitis (related to HLA-B27) or lower limb arthritis. Other gastrointestinal diseases associated with arthropathy include bypass surgery, Whipple disease, Behcet syndrome, and celiac disease. Amebic colitis is caused by ingestion of infectious cysts (typically from Entamoeba histolytica). Symptoms include abdominal pain and diarrhea; malaise and weight loss also may occur. Cecal amebiasis can resemble acute appendicitis. Chronic appendicitis may be asymptomatic or cause poorly defined abdominal pain. Diverticulosis is usually a disease of older adults. It is often asymptomatic unless inflammation supervenes. Pseudomembranous colitis is a severe form of diarrhea usually seen in the setting of prior antibiotic use. The causative organism is almost always Clostridium difficile.

Choose the correct answer

Correct! Wrong!

The two principal causes of rapidly progressive glomerulonephritis are anti-glomerular basement membrane (including both Goodpasture syndrome and isolated anti-glomerular basement disease) and primary systemic vasculitis (including Wegener granulomatosis, microscopic polyarteritis, idiopathic rapidly progressive glomerulonephritis, Churg-Strauss syndrome, polyarteritis nodosa, giant-cell arteritis, and Takayasu arteritis). A very large variety of other systemic and primary glomerular disease may occasionally cause rapidly progressive glomerulonephritis, but this is usually not the typical presentation for these diseases. Diabetic nephropathy typically begins with microalbuminuria and hypertension and progresses over a 10- to 20-year period to renal failure. Hypertensive nephropathy due to essential hypertension typically presents with slowly rising BUN and creatinine; hypertensive nephropathy due to malignant hypertension presents with more rapidly rising BUN and creatinine. Lupus nephritis can have many presentations, but the most typical is proteinuria, which may be severe enough to cause nephrotic syndrome. Also, 90% of cases of systemic lupus erythematosus occur in women, usually of child-bearing age. Minimal change disease typically presents with nephrotic syndrome and is not consistently associated with recognizable glomerular changes by light microscopy. Podocyte foot-process fusion can be seen by electron microscopy.

Choose the correct answer

Correct! Wrong!

Seventy percent of adult brain tumors occur above the tentorium (70% of childhood tumors occur below the tentorium). Statistically, metastases > astrocytomas (including glioblastoma) > meningioma > pituitary tumor. Location at the junction of cortical gray and white matter is also typical for metastatic disease, as is the round shape. Astrocytomas typically arise in the white matter and have an irregular shape. Ependymomas are uncommon and arise from the ependymal lining of the ventricles. Glioblastoma multiforme is an aggressive form of astrocytoma that can cause a “butterfly lesion,” crossing between the cerebral hemispheres. Meningiomas can cause spherical lesions and are usually located on the surface of the brain.

Choose the correct answer

Correct! Wrong!

The recurrent laryngeal nerve is a branch of the vagus nerve, which innervates all the intrinsic laryngeal muscles except the cricothyroid muscle. The cricothyroid is attached to the cricoid cartilage and the thyroid cartilage; contraction of this muscle tends to stretch and adduct the vocal ligament. The cricothyroid is innervated by the external laryngeal nerve. The lateral cricoarytenoid muscle is innervated by the recurrent laryngeal nerve and is attached to the cricoid cartilage and the arytenoid cartilage. Its contraction causes adduction of the vocal ligament. The posterior cricoarytenoid muscle is innervated by the recurrent laryngeal nerve and is attached to the cricoid cartilage and the arytenoid cartilage. Its contraction causes abduction of the vocal ligament. The thyroarytenoid muscle is innervated by the recurrent laryngeal nerve and is attached to the thyroid cartilage and the arytenoid cartilage. Its contraction causes slackening of the vocal ligament. The vocalis muscle is the most medial part of the thyroarytenoid muscle. It attaches either to the thyroid cartilage and the vocal ligament, or to the arytenoid cartilage and the vocal ligament. It is innervated by the recurrent laryngeal nerve. Its contraction causes tension on segments of the vocal ligament.

Choose the correct answer

Correct! Wrong!

In fully compensated aortic coarctation, blood flow is normal in the lower and upper body despite an increased arterial pressure (about 50% higher) in the upper body compared with the pressure in the lower body. Because resistance = pressure/blood flow, it is clear that resistance must be lower in the lower portions of the body. The mechanism of this decrease in resistance below the constriction (and increased resistance above the constriction) is autoregulation of blood flow. The small arteries and arterioles dilate (or constrict) in accordance with the metabolic needs of the tissues, ensuring that each tissue receive an adequate amount of blood flow. Thus, the increase in blood pressure in the upper body leads to constriction of the arterioles, which increases vascular resistance, and the lower pressure below the coarctation leads to dilation of the arterioles, which decreases vascular resistance.

Comments are closed.