USMLE Step 1 Qs (2)

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USMLE Step 1 Qs (2) - Quiz

Questions from various sources for practicing


Questions and Answers
  • 1. 

    The structures labeled in the figure with an asterisk produce which of the following substances?

    • A.

      Acid

    • B.

      Mucus and HCO3–

    • C.

      Pepsinogen

    • D.

      Lysozyme

    • E.

      Enterokinase

    Correct Answer
    B. Mucus and HCO3–
    Explanation
    The presence of the mucus and bicarbonate (HCO3–) secreting Brunner's glands (labeled with the asterisks) in the submucosal layer of the intestine is an identifying feature of the duodenum. The Brunner's gland secretions function to neutralize the acidic pH of the stomach and establish the appropriate pH for function of the enzymes in the pancreatic juice. Parietal cells are unique to the stomach (with the exception of Meckel's diverticulum and Barrett's esophagus) and synthesize acid and gastric intrinsic factor (required for vitamin B12 absorption from the small intestine). Chief cells in the fundic glands produce pepsinogen that is activated by acid to form pepsin. Paneth cells in the base of the crypts make lysozyme and modulate the flora of the small intestine. Enterokinase is made by the duodenal mucosa and is instrumental in the conversion of pancreatic zymogens to their active form (e.g., trypsinogen to trypsin).

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  • 2. 

    In hemolytic jaundice, the structure labeled with the arrow in the accompanying photomicrograph will contain which of the following?

    • A.

      Elevated urobilinogen levels

    • B.

      Elevated bilirubin levels

    • C.

      Decreased urobilinogen levels

    • D.

      Decreased bilirubin levels

    • E.

      Elevated numbers of lymphocytes undergoing diapedesis

    Correct Answer
    B. Elevated bilirubin levels
    Explanation
    The structure labeled with the arrow is a bile duct and would contain elevated levels of bilirubin following hemolytic jaundice. Hemolytic jaundice is associated predominantly with unconjugated hyperbilirubinemia. The overproduction of bilirubin occurs because of accelerated intravascular erythrocyte destruction or resorption of a large hematoma. When the hepatic uptake and/or excretion of urobilinogen is (are) impaired or the production of bilirubin is greatly increased (e.g., with hemolysis) daily urinary urobilinogen excretion may increase significantly. In contrast, cholestasis [arrested flow of bile due to obstruction of the bile ducts (intrahepatic)] or extrahepatic biliary obstruction interferes with the intestinal phase of bilirubin metabolism and leads to significantly decreased production and urinary excretion of urobilinogen. Diapedesis of lymphocytes across the endothelium of the postcapillary high endothelial venules of lymphoid organs (e.g., lymph nodes) increases during inflammation.

    Bile is formed by the hepatocytes and is released into bile canaliculi, which are located between the lateral surfaces of adjacent hepatocytes. The direction of flow is from the hepatocytes toward the bile duct, which drains bile from the liver on its path to the gallbladder, where the bile is stored and concentrated. The hepatic artery and hepatic portal vein (shown in the photomicrograph) plus the bile duct comprise the portal triad. Blood flows from the triad (hepatic artery, portal vein, and bile duct) toward the central vein, whereas bile flows in the opposite direction toward the triad.

    Bile is synthesized by hepatocytes using the smooth endoplasmic reticulum (SER) and consists of bile acids and bilirubin. Bile acids are 90% reused from the distal small and large intestinal lumen and 10% newly synthesized by conjugation of cholic acid, glycine, and taurine in the SER. Bilirubin is the breakdown product of hemoglobin derived from the action of Kupffer cells in hepatic sinusoids and other macrophages, particularly those lining the sinusoids of the spleen where degradation of RBCs is prominent.

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  • 3. 

    A 42-year-old woman (5 ft, 3in., 170 lb) complains of sudden onset of severe pain in the right upper abdomen "under the ribs" accompanied by sweating, nausea, and a feeling of imminent collapse. The pain lasts for about two hours and then persists as a dull ache. When seen several hours later, she has normal bowel sounds, is tender throughout the abdomen, especially in the right upper quadrant, and is faintly icteric. She has noticed her urine is darker than usual but has not passed stool recently. She recalls occasional episodes of "indigestion" referred to the right upper abdomen and radiating to the shoulder. This has occurred especially after eating fried foods or after eating a meal following a long period of fasting. She has no fever but is anxious and tachycardic. The tests available are a blood count and blood chemistry including liver enzymes, alkaline phosphatase, and bilirubin. She has a WBC of 10,000. Her cellular hepatic enzymes are: AST/SGOT = 52 (2-33) and ALT/SGPT = 70 (4 to 44), alkaline phosphatase = 300 (17 to 91), bilirubin = 6.3 (0.2 to 1.0). Which of the following is the most likely diagnosis?

    • A.

      Hepatitis A

    • B.

      Hepatitis B

    • C.

      Carcinoma of the head of the pancreas

    • D.

      Gallstone obstructing common bile duct

    • E.

      Biliary cirrhosis

    Correct Answer
    D. Gallstone obstructing common bile duct
    Explanation
    The most probable diagnosis is gallstones. The pattern of elevated liver enzymes, alkaline phosphatase, and bilirubin are consistent with obstructive jaundice (see table below). The presence of pain (in the right upper quadrant radiating to the shoulder) after eating a meal consisting of fried foods makes gallstones the most probable diagnosis. Similar pain often occurs in these patients when they have not eaten for long periods of time and then have a large meal. The pain is caused by the obstruction of the cystic duct or common bile duct that produces increased lumenal pressure within the bile vessels, which cannot be compensated for by cholecytokinin-induced contractions. The pain lasts for about one to four hours as a steady, aching feeling.
    Enzyme Obstructive Parenchymal
    Liver enzymes
    (AST and ALT) ↑ ↑↑↑
    Alkaline phosphatase ↑↑↑ ↑
    Bilirubin ↑↑↑ ↑↑↑

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  • 4. 

    A pheochromocytoma is a common tumor of the adrenal medulla. In the presence of this tumor, which of the following symptoms would most likely be observed?

    • A.

      Hypotension

    • B.

      Hypoglycemia

    • C.

      Hirsutism

    • D.

      Decreased metabolic rate

    • E.

      Paroxysms

    Correct Answer
    E. Paroxysms
    Explanation
    Patients with a pheochromocytoma often have paroxysms that are the hallmark of this tumor. These are seizure-like catecholamine-induced attacks that include headache, profuse sweating, palpitations, and overall anxiety. Pheochromocytoma is a common tumor of the adrenal medulla that leads to an excess of norepinephrine, which causes hypertension and hyperglycemia. Vasoconstriction of arterioles occurs in conjunction with the increased blood pressure. Epinephrine (e.g., cortisol and growth hormone) have anti-insulin effects, thus causing hyperglycemia.

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  • 5. 

    During the physical examination of a newborn child, it was observed that the genitalia were female, but masculinized. The genotype was determined to be 46,XX. Which of the following is the most likely cause of this condition?

    • A.

      Androgen insensitivity

    • B.

      Decreased blood ACTH levels

    • C.

      Atrophy of the zona reticularis

    • D.

      A defect in the cortisol pathway

    • E.

      Hypersecretion of vasopressin

    Correct Answer
    D. A defect in the cortisol pathway
    Explanation
    The newborn described is genotypically female and suffers from adrenogenital or congenital virilizing hyperplasia in which there is a deficiency in the pathway that leads to cortisol synthesis. The inability to synthesize cortisol in turn leads to production of high levels of ACTH and ACTH-releasing factor from the hypothalamus. The result is hypertrophy of the fetal adrenal cortex, which is a critical fetal structure that produces dehydroepiandrosterone. The excessive production of androgens by the fetal adrenal leads to masculinization of the female genitalia. Increased secretion of cortisol cannot occur because of the metabolic defect in this pathway; therefore, negative feedback control is not functional. The fetal cortex is part of maternal-feto-placental unit because the dehydroepiandrosterone is used by the placenta to produce estradiol. The fetal adrenal cortex involutes following birth, causing an overall reduction in the size of the adrenal. The adult cortex (zona glomerulosa, zona fasciculata, and zona reticularis) replaces the fetal adrenal cortex. The zona fasciculata and zona reticularis produce androgens after birth. Vasopressin [AVP; also known as antidiuretic hormone (ADH)] is released by the posterior pituitary and regulates fluid balance. ADH increases the permeability of the collecting duct through an aquaporin-mediated mechanism. Androgen insensitivity is the cause of testicular feminization and is not a factor in the adrenogenital syndrome.

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  • 6. 

    A pituitary adenoma is likely to result in which of the following clinical conditions?

    • A.

      Cushing's syndrome

    • B.

      Deficiency in T3 and T4

    • C.

      Diabetes insipidus

    • D.

      Osteoporosis

    • E.

      Stunted growth or dwarfism

    Correct Answer
    A. Cushing's syndrome
    Explanation
    Pituitary adenomas are anterior pituitary specific. A corticotroph-adenoma would cause increased levels of ACTH and stimulate excessive production of corticosteroids from the adrenal cortex (Cushing's syndrome). LH and FSH-producing gonadotrophs occur but tend to result in hypogonadism. Somatotropic tumors produce GH and cause giantism. Prolactinomas are the most common form of pituitary adenoma resulting in infertility, galactorrhea (excessive production of milk), and amenorrhea. Diabetes insipidus is caused by absence of vasopressin [arginine vasopressin (AVP)], leading to excretion of a large quantity of dilute fluid (hypotonic polyuria). Overproduction of parathyroid hormone (PTH) leads to osteoporotic changes, but PTH is not regulated by the anterior pituitary.

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  • 7. 

    A tumor in the specific region denoted by the asterisks will most likely cause which of the following clinical conditions?

    • A.

      Diabetes

    • B.

      Hypoglycemia

    • C.

      Elevated blood pressure

    • D.

      Decreased blood pressure

    • E.

      Increased bone resorption

    Correct Answer
    A. Diabetes
    Explanation
    A tumor of the glucagon secreting alpha ( ) or A cells delineated with the asterisks results in hyperglycemia and diabetes. This photomicrograph shows both exocrine and endocrine portions of the pancreas. Pancreatic exocrine tissue is found throughout the pancreas with round aggregation of lighter staining cells forming the islets of Langerhans. There are several endocrine cell types within the islets. The more numerous (70% of total) B or cells are centrally located and secrete insulin that is secreted after a meal and results in a lowering of blood sugar. The smaller population of A or cells located at the periphery of the islet (*) secrete glucagon. Glucagon is secreted in response to low blood sugar and raises blood sugar levels. A glucagonoma produces excessive amounts of glucagon that results in hyperglycemia and diabetes. The interaction of alpha and beta cells is based on the blood supply. Blood entering the islet initially bypasses the alpha cells. The result is that blood reaching the alpha cells already contains insulin, which regulates glucagon production. The absence of normal glucagon regulation by insulin is a further complication in type I diabetes in which insulin is not produced. Other cell types [D (delta ) and F)] are variable in location and secrete somatostatin and pancreatic polypeptide, respectively. Somatostatin regulates insulin and glucagon release, whereas pancreatic polypeptide appears to regulate exocrine protein and bicarbonate secretion. The exocrine portion of the pancreas consists of acinar and ductal cells. The acinar cells are pyramidal in shape and possess a very basophilic basal cytoplasm, indicating the presence of abundant rough ER and an acidophilic apical cytoplasm due to the presence of numerous secretory (zymogen) granules. Other tumors of the islets of Langerhans include insulinomas in which elevated levels of insulin are secreted into the bloodstream. The result is hypoglycemia as blood sugar levels drop. There is decreased storage of glycogen in the liver, inhibition of hepatic phosphorylase (which causes the breakdown of glycogen to form glucose), and increased glucose metabolism in muscle.

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  • 8. 

    Which of the following is the function of the organ shown in the photomicrograph below?

    • A.

      Passage of urine and sperm in the male

    • B.

      Passage of urine in the female

    • C.

      Passage of urine from the bladder to the urethrae in males and females

    • D.

      Passage of sperm from the epididymis to the urethra

    • E.

      Storage of sperm and absorption of fluid

    Correct Answer
    D. Passage of sperm from the epididymis to the urethra
    Explanation
    The organ shown in the figure is the vas deferens (ductus deferens). The vas deferens conducts sperm from the epididymis to the urethra. The thick muscular wall is unique in the presence of an inner longitudinal, a middle circular, and an outer longitudinal layer of smooth muscle. The ureter has two thin layers of muscle: inner longitudinal and outer circular. The male and female urethra contain extensive vascular channels. The epididymis consists of a connective tissue stroma and stores sperm, resorbs fluid, and produces sperm maturation factors.

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  • 9. 

    Which of the following organs is shown in the figure below?

    • A.

      Female urethra

    • B.

      Male urethra

    • C.

      Oviduct

    • D.

      Ureter

    • E.

      Seminal vesicle

    Correct Answer
    B. Male urethra
    Explanation
    The photomicrograph is the male (penile) urethra. It possesses a primarily pseudostratified columnar type of epithelium. The glands of Littre that produce mucus are also observed in the section. The thick-walled arteries of the penile and cavernous sinuses of penile erectile tissue are also a distinguishing feature of this organ. Helicine arteries supply the sinuses. Action of the parasympathetic nervous system mediates the dilatation of these vessels during erection.

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  • 10. 

    The organ shown in this photomicrograph is responsible for production of which of the following substances?

    • A.

      Spermine and fibrolysin

    • B.

      T3 and T4

    • C.

      Proteins that coagulate semen

    • D.

      Acid phosphatase

    • E.

      Milk

    Correct Answer
    C. Proteins that coagulate semen
    Explanation
    The organ shown in the light microscopic photograph is the seminal vesicle that produces fructose, ascorbic acid, prostaglandins, and proteins responsible for semen coagulation. The seminal vesicle produces about 50% of the seminal fluid on a volume basis and comprises most of the ejaculate. The wall consists of smooth muscle and the mucosa of anastomosing "villus-like" folds. In comparison, the prostate is composed of 15 to 30 tubuloalveolar glands surrounded by fibromuscular tissue. Concretions are often found in the lumina. The prostate secretes a thin, opalescent fluid that contributes primarily to the first part of the ejaculate. Prostatic secretions include acid phosphatase, spermine (a polyamine), fibrolysin, amylase, and zinc. Spermine oxidation results in the musky odor of semen, and fibrolysin is responsible for the liquefaction of semen after ejaculation. Acid phosphatase and prostatic-specific antigen are important for the diagnosis of metastases.

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  • 11. 

    The organ pictured in the photomicrograph performs which of the following functions?

    • A.

      The site of spermiogenesis

    • B.

      Production of fructose and prostaglandins

    • C.

      Phagocytosis of sperm and residual bodies

    • D.

      The site of implantation

    • E.

      The site of milk production

    Correct Answer
    C. Phagocytosis of sperm and residual bodies
    Explanation
    The figure is a light microscopic photograph of the epididymis. The epididymis functions in the storage, maturation, and phagocytosis of sperm and residual bodies. In addition, the epididymis is involved in the absorption of testicular fluid and the secretion of glycoproteins. These glycoproteins may be involved in the inhibition of capacitation. The epithelium of the epididymis is pseudostratified with stereocilia (modified microvilli for absorption), and the wall contains extensive connective tissue. The seminal vesicle produces fructose and prostaglandins and contains a thick smooth muscle layer. Sperm are often found in the lumina. Spermiogenesis occurs in the testes. Milk production occurs in the mammary gland, which contains alveoli and lactiferous ducts. Implantation occurs in the uterus, which is lined by a simple columnar epithelium with endometrial glands that differ in arrangement, depending on the phase of the cycle (long and straight in the proliferative phases and S-shaped in the secretory phase). The myometrium, composed of smooth muscle, is hormone-sensitive and undergoes both hypertrophy and hyperplasia during pregnancy and atrophy after menopause, resulting in a shrinking of the uterus in postmenopausal women.

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  • 12. 

    . The urologist may describe the reattachment of a severed vas deferens (vasovasostomy) as successful, more than 90% of the time. However, it is unsuccessful from the patients' point of view since a much lower percentage of these men can father a child. The difference in success rate is due to which of the following facts?

    • A.

      Spermatogonia are exposed to humoral factors

    • B.

      Genetic recombination in haploid sperm creates novel antigens

    • C.

      Cryptorchid testes are often incapable of producing fertile sperm

    • D.

      Vasectomy prevents phagocytosis of sperm by macrophages

    • E.

      Sperm coated with autoimmune antibodies are unable to fertilize an egg.

    Correct Answer
    E. Sperm coated with autoimmune antibodies are unable to fertilize an egg.
    Explanation
    Attempts to counteract or repair the effects of a vasectomy (vasovasostomy) are often unsuccessful because of the development of antisperm antibodies. This lack of success occurs despite the fact that 90% of the patients undergoing vasovasostomy have sperm return to the ejaculate. In the case of vasectomy, sperm that have leaked from the severed vas deferens is viewed as foreign by immune surveillance and antibodies develop. The phagocytosis of sperm by macrophages plays a role in the development of antisperm antibodies that occurs following the ligation or removal of a segment of the vas deferens. Attempted reunion of the ligated segments is called vasovasostomy and may return sperm to the ejaculate; however, the presence of antisperm antibodies may prevent normal fertilization. Sperm are immunologically foreign because of a number of factors. Spermatogenesis begins at puberty long after the development of self-recognition in the immune system. The blood-testis barrier protects developing sperm from exposure to systemic factors. The basal compartment containing the spermatogonia and preleptotene spermatocytes is exposed to plasma; however, the adluminal compartment, which contains primary and secondary spermatocytes, spermatids, and testicular sperm, prevents these antigens from entering the blood. The inability of cryptorchid testes to produce fertile sperm is related to the higher temperature in the abdomen than in the normal scrotal location.

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  • 13. 

    Which of the following are characteristic of the secretory phase of the menstrual cycle?

    • A.

      It precedes ovulation

    • B.

      It depends on progesterone secretion by the corpus luteum

    • C.

      It coincides with the development of ovarian follicles

    • D.

      It coincides with a rapid drop in estrogen levels

    • E.

      It produces ischemia and necrosis of the stratum functionale

    Correct Answer
    B. It depends on progesterone secretion by the corpus luteum
    Explanation
    The secretory phase of the menstrual cycle depends on progesterone secretion and follows the proliferative (follicular) phase. The menstrual phase occurs after the secretory phase. During the follicular phase (approximately days 4 to 16), estrogen produced by the ovaries drives cell proliferation in the base of endometrial glands and the uterine stroma. The proliferative phase culminates with ovulation. The secretory phase (approximately days 16 to 25) is characterized by high progesterone levels from the corpus luteum, a tortuous appearance of the uterine glands, and apocrine secretion by the gland cells. During this phase, maximum endometrial thickness occurs. The menstrual phase (approximately days 26 to 30) is characterized by decreased glandular secretion and eventual glandular degeneration because of decreased production of both progesterone and estrogen by the theca lutein cells. Contraction of coiled arteries and arterioles leads to ischemia and necrosis of the stratum functionale.

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  • 14. 

    A 33-year-old patient with an average menstrual cycle of 28 days comes in for a routine Pap smear. It has been 35 days since the start of her last menstrual period, and a vaginal smear reveals clumps of basophilic cells. As her physician, you suspect which of the following?

    • A.

      She will begin menstruating in a few days

    • B.

      She will ovulate within a few days

    • C.

      Her serum progesterone levels are very low

    • D.

      There are detectable levels of hCG in her serum and urine

    • E.

      She is undergoing menopause

    Correct Answer
    D. There are detectable levels of hCG in her serum and urine
    Explanation
    The patient described in this question is probably pregnant. The delay in menstruation coupled with the presence of basophilic cells in a vaginal smear are clues. Ovulation is the midpoint of the cycle and should be more than a few days away. She is relatively young for the onset of menopause and there are no other symptoms. The vaginal epithelium varies little with the normal menstrual cycle. Exfoliative cytology can be used to diagnose cancer and to determine if the epithelium is under stimulation of estrogen and progesterone. The presence of basophilic cells in the smear with the Pap-staining method would indicate the presence of both estrogen and progesterone. The data suggest the maintenance of the corpus luteum (i.e., pregnancy).

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  • 15. 

    In the accompanying transmission electron micrograph from the renal corpuscle, which of the following are the structures labeled with arrows?

    • A.

      Podocyte foot processes

    • B.

      Endothelial cell fenestrations

    • C.

      Pedicels

    • D.

      Filtration slits

    • E.

      The lamina rara of the basement membrane

    Correct Answer
    D. Filtration slits
    Explanation
    The transmission electron micrograph illustrates the filtration barrier of the renal corpuscle. The structures labeled with arrows are the filtration slits, which are located between adjacent pedicels (foot processes of the podocytes). The remainder of the filtration barrier is formed by the glomerular basement membrane, which contains type IV collagen and heparan sulfate. There are three distinct layers within the glomerular basement membrane: (1) an electron-dense lamina densa in the center surrounded by (2) the lamina rara externa on the glomerular side and by (3) the lamina rara interna on the capillary endothelial side.

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  • 16. 

    Renal changes in the kidney in a patient with diabetes mellitus of 30 years duration may result in which of the following?

    • A.

      Decreased permeability to plasma proteins

    • B.

      Enhanced selectivity of the filtration barrier

    • C.

      Hyperalbuminemia

    • D.

      A generalized increase in osmotic pressure

    • E.

      Compensatory secretion of aldosterone

    Correct Answer
    E. Compensatory secretion of aldosterone
    Explanation
    In patients who have suffered from diabetes mellitus for many years there is compensatory release of aldosterone. The initial change is the thickening of the glomerular basement membrane. The separation of laminae rarae and densa is obliterated, which results in a loss of selectivity of the filtration barrier. This causes the loss of protein from the blood to the urine (proteinuria). The liver adjusts to the proteinuria by producing more proteins (e.g., albumin). After continued proteinuria, the liver is unable to produce sufficient protein, which results in hypoalbuminemia. This leads to an overall decrease in osmotic pressure. The result is edema as fluid leaves the vasculature to enter the tissues. The movement of fluid from the vasculature to the tissues results in reduced plasma volume and decreased glomerular filtration rate (GFR). The overall effect is further edema because of compensatory release of aldosterone coupled with reduced GFR and the already existing edema. These renal changes are known as nephrotic syndrome. The foot processes are affected in many diseases, such as diabetes mellitus, that lead to nephrotic syndrome. Loss of anionic charge and fusion of the foot processes result in the obliteration of the filtration slits.

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  • 17. 

    Which of the following is involved in glomerular filtration

    • A.

      Facilitated diffusion of large anionic proteins

    • B.

      Maintenance of a charge barrier

    • C.

      A physical barrier consisting of type II collagen

    • D.

      Filtration slits between adjacent endothelial cells

    • E.

      A positive charge in the basement membrane due to the presence of heparan sulfate

    Correct Answer
    B. Maintenance of a charge barrier
    Explanation
    The glomerular filtration barrier is a physical and charge barrier that exhibits selectivity based on molecular size and charge. The barrier is formed by three components: (1) glomerular capillary endothelial cells, (2) glomerular basement membrane, and (3) podocyte layer. The presence of collagen type IV in the lamina densa of the basement membrane presents a physical barrier to the passage of large proteins from the blood to the urinary space. Glycosaminoglycans, particularly heparan sulfate, produce a polyanionic charge that binds cationic molecules. Filtration slits are found between adjacent podocyte foot processes and provide a gap of approximately 50 m. The foot processes are coated with a glycoprotein called podocalyxin, which is rich in sialic acid and provides mutual repulsion to maintain the structure of the filtration slits. It also possesses a large polyanionic charge for repulsion of large anionic proteins.

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  • 18. 

    Visual transduction involves which of the following?

    • A.

      Inactivation of phosphodiesterase

    • B.

      Increase in cGMP levels

    • C.

      Conversion of all-trans-retinal to 11-cis retinal

    • D.

      Closing of a Na+ channel

    • E.

      Depolarization of the rod cell membrane

    Correct Answer
    D. Closing of a Na+ channel
    Explanation
    Visual transduction involves closing of the Na+ channel in rod cells in response to photons of light. Rhodopsin is the visual pigment of rod cells and is composed of retinal, a vitamin A derivative, bound to opsins. Photons reaching rhodopsin isomerize retinal to the all-trans form from 11-cis retinal. The result is bleaching, which represents the dissociation of retinal from the opsins. The bleaching process results in a fall in cGMP within the cytosol. Transducin is a G protein that couples bleaching to cGMP through the action of a phosphodiesterase enzyme that cleaves cGMP to GMP. The closing of the Na+ channel results in a reduction in permeability to sodium ions and hyperpolarization of the cell membrane. The signal spreads to the inner segment and through gap junctions to nearby photoreceptor cells. In the presence of cGMP, the Na+ channel remains open; in its absence, the channel closes and the cell hyperpolarizes. Therefore, the rods and cones differ from other receptors in that hyperpolarization of the cell membranes occurs rather than the depolarization that occurs in other neural systems. Closing the channel slows down the release of the visual transmitter.

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  • 19. 

    An elderly gentleman is delivered to the hospital in a febrile and septic condition. The only remarkable recent history was an episode of choking on swallowing a rough object during a meal a few days previously. The choking resolved, but there was some hematemesis the following day that also resolved. The examiner notes edematous pharyngeal tissue and assumes an esophageal laceration with infection within the retrovisceral space. The examining physician suspects that the infection

    • A.

      Tracks superiorly and inferiorly within the carotid sheath

    • B.

      Extends anteriorly to the trachea

    • C.

      Extends into the posterior mediastinum

    • D.

      Will not extend below the manubrium

    Correct Answer
    C. Extends into the posterior mediastinum
    Explanation
    The retropharyngeal (retrovisceral) space descends into the posterior mediastinum. Infection in the retrovisceral space may track deep into the posterior thorax, a life-threatening condition. Conversely, the pretracheal space, deep to the pretracheal fascia, surrounds the trachea and thyroid gland, but is anterior to the esophagus. It descends into the superior mediastinum to about the level of the manubrium.

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  • 20. 

    A carcinoma in the medial portion of the lower lip is most likely to first metastasize via which of the following lymph nodes?

    • A.

      Submandibular lynph nodes

    • B.

      Parotid lymph nodes

    • C.

      Superficial cervical lymph nodes

    • D.

      Submental lymph nodes

    • E.

      Buccal lymph nodes

    Correct Answer
    D. Submental lymph nodes
    Explanation
    Lymph from the medial portion of the lower lip preferentially drains through the submental nodes in the chin and metastases may first appear here. Lymph from the upper lip and lateral portions of the lower lip drains preferentially through the submandibular nodes on the inferolateral aspect of the mandible. The parotid nodes receive lymph from upper and lateral regions of the face including the forehead, eyelids, and middle ear. Superficial and deep cervical nodes receive lymph from other nodes including the parotid and retroauricular. Buccal lymph nodes drain the cheeks and sides of the nose.

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  • 21. 

    The arachnoid villi allow cerebrospinal fluid to pass between which of the following two spaces?

    • A.

      Choroid plexus and subdural space

    • B.

      Subarachnoid space and subdural space

    • C.

      Subarachnoid space and superior sagittal sinus

    • D.

      Subdural space and cavernous sinus

    • E.

      Superior sagittal sinus and jugular vein

    Correct Answer
    C. Subarachnoid space and superior sagittal sinus
    Explanation
    Cerebrospinal fluid formed in the choroid plexus circulates in the subarachnoid space and is absorbed by the venous sinuses through the arachnoid villi, some of which project into the superior sagittal sinus. Cerebrospinal fluid protects the nervous system from concussions and mechanical injuries and is important for metabolism. It circulates slowly through the ventricles of the brain and through the meshes of the subarachnoid space.

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  • 22. 

    An elderly man, persuaded to have his eyes examined after a series of minor automobile accidents, was found to have a pituitary adenoma that was producing visual field defects. A pituitary adenoma that expands superiorly and compresses the central portion of the optic chiasm will result in which of the following?

    • A.

      Total blindness

    • B.

      Losses of left and right inferior fields of vision

    • C.

      Losses of left and right nasal fields of vision

    • D.

      Losses of left and right temporal fields of vision

    Correct Answer
    D. Losses of left and right temporal fields of vision
    Explanation
    A tumor that impinges on and compresses the optic chiasm will produce tunnel vision (bitemporal heteronymous hemianopsia). The reason for this pattern of blindness is that the lens projects reversed and inverted lateral visual fields onto the nasal portions of the retina. The pathways from the nasal retinas cross in the optic chiasm. This decussation collects both right and left visual fields. Thus, nerve fibers from the right nasal retina and left temporal retina, e.g., are collected into the left optic tract for projection to the left lateral geniculate body and then to the left occipital cortex. Injury to a lateral portion of the chiasm produces ipsilateral nasal hemianopsia, the loss of the nasal field from one eye. A lesion of the optic nerve would produce complete blindness of that eye, whereas a lesion to the optic tract produces contralateral homonymous hemianopsia, complete loss of the contralateral visual field.

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  • 23. 

    Which of the following statements concerning the lacrimal apparatus is correct?

    • A.

      The lacrimal gland lies in the medial portion of the orbit

    • B.

      Lacrimal fluid is secreted at the puncta in the medial edges of both upper and lower lids

    • C.

      The nasolacrimal duct has a blind-ending lacrimal sac at its upper portion

    • D.

      The nasolacrimal duct ends in the middle meatus of the nose

    Correct Answer
    C. The nasolacrimal duct has a blind-ending lacrimal sac at its upper portion
    Explanation
    The lacrimal gland lies in the upper lateral portion of the orbit. Normally, lacrimal fluid flows across the cornea to enter puncta in the medial edges of both upper and lower lids. From the puncta, canaliculi run to enlarged ampullae. The nasolacrimal duct has a blind–ending lacrimal sac at its upper portion that is squeezed like a bulb syringe by the opening and closing of the eyelids and thereby aspirates the lacrimal fluid. The nasolacrimal duct ends in the inferior meatus of the nose.

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  • 24. 

    Tic douloureux (trigeminal neuralgia) is characterized by sharp pain over the distribution of the trigeminal nerve. This syndrome involves neurons that have their cell bodies in which of the following?

    • A.

      Geniculate ganglion

    • B.

      Otic ganglion

    • C.

      Pterygopalatine ganglion

    • D.

      Submandibular ganglion

    • E.

      Trigeminal ganglion

    Correct Answer
    E. Trigeminal ganglion
    Explanation
    The cell bodies of most of the sensory neurons of the trigeminal nerve are located in the trigeminal ganglion. From there they project to the nucleus of the spinal tract and ultimately to the ventral posterior medial nucleus of the thalamus. From this point, they project to the medial portions of the sensory cortex of the postcentral gyrus. The otic, pterygopalatine, and submandibular ganglia are parasympathetic. The geniculate ganglion contains the sensory neurons of the facial nerve.

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  • 25. 

    . In dislocation of the jaw, displacement of the articular disk beyond the articular tubercle of the temporomandibular joint results from spasm or excessive contraction of which of the following muscles

    • A.

      Buccinator

    • B.

      Lateral pterygoid

    • C.

      Medial pterygoid

    • D.

      Masseter

    • E.

      Temporalis

    Correct Answer
    B. Lateral pterygoid
    Explanation
    The temporalis, masseter, and medial and lateral pterygoid muscles attach to the mandible and are the major muscles involved in movements of the jaw. The buccinator muscle, which controls the contents of the mouth during mastication, is innervated by the seventh cranial nerve and constitutes the chief muscle of facial expression. The lateral pterygoid muscles, acting bilaterally, protract the jaw and, acting unilaterally, rotate the jaw during chewing. Because the fibers of the superior head of the lateral pterygoid muscle insert onto the anterior aspect of the articular disk of the temporomandibular joint as well as onto the head of the mandible, spasm of this muscle, such as in a yawn, can result in dislocation of the mandible by pulling the disk anterior to the articular tubercle. Reduction is accomplished by pushing the mandible downward and back, so that the head of the mandible reenters the mandibular fossa. The temporalis, medial pterygoid, and masseter muscles primarily elevate the jaw in molar occlusion.

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  • 26. 

    A patient is found to have internal (medially directed) strabismus of the left eye, paralysis of the muscles of facial expression on the left side, hyperacusis (louder perception of sounds) of the left ear, and loss of taste from the anterior two-thirds of the tongue on the left. The mouth is somewhat drier than normal. In addition, in the left eye there is a lack of tearing, and a blink reflex cannot be elicited from the stimulation of either the right or the left cornea. There is accompanying upper motor neuron paralysis of the right side of the body. Internal strabismus (deviation of the eye medially) results from paralysis of which of the following cranial nerves?

    • A.

      Cranial nerve II

    • B.

      Cranial nerve III

    • C.

      Cranial nerve IV

    • D.

      Cranial nerve V

    • E.

      Cranial nerve VI

    Correct Answer
    E. Cranial nerve VI
    Explanation
    The abducens nerve (CN VI) innervates the lateral rectus muscle. Loss of innervation to the lateral rectus results in unopposed tension by the medial rectus, which produces internal strabismus. The oculomotor nerve (CN III) innervates the medial, superior, and inferior recti, the inferior oblique, and the levator palpebrae superioris muscles. Paralysis of this nerve would result in lateral deviation of the eye (external strabismus) accompanied by ptosis (drooping eyelid). In addition, mydriasis (dilated pupil) results from loss of function of the parasympathetic component of the oculomotor nerve. Damage to the trochlear nerve (CN IV) results in paralysis of the superior oblique muscle with impaired ability to direct the eye downward and outward.

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  • 27. 

    A teenage baseball player was hit in the base of the skull by a loose bat. The patient is hoarse and complains of difficulty swallowing. The cranial x-ray indicates a basal skull fracture that passes through the jugular foramen. The examining physician notes a large hematoma behind the ear on the injured side. If the nerves passing through the jugular foramen were severed as a result of the cranial fracture, which of the following is the one muscle that would remain functional?

    • A.

      Palatoglossus muscle

    • B.

      Sternomastoid muscle

    • C.

      Styloglossus muscle

    • D.

      Stylopharyngeus muscle

    • E.

      Trapezius muscle

    Correct Answer
    C. Styloglossus muscle
    Explanation
    The styloglossus muscle is innervated by the hypoglossal nerve, which leaves the posterior cranial fossa by way of the anterior condylar canal. In addition to the internal jugular vein, the jugular foramen contains the glossopharyngeal nerve (innervating the stylopharyngeus muscle), the vagus nerve (innervating palatal, pharyngeal, and laryngeal musculature), and the spinal accessory nerve (innervating the sternomastoid and trapezius muscles).

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  • 28. 

    Specialized cardiac muscle cells that control the rate of the heartbeat are found in which of the following sites?

    • A.

      In the muscular wall of the interventricular septum

    • B.

      In the arch of the aorta

    • C.

      In the wall of the left atrium between openings of the pulmonary veins

    • D.

      In the wall of the right atrium near the opening of the superior vena cava

    • E.

      On the surface of the heart

    Correct Answer
    D. In the wall of the right atrium near the opening of the superior vena cava
    Explanation
    Specialized cardiac muscle cells, which form the sinoatrial (SA) node, are the pacemakers of the heartbeat. They have the fastest-paced autorhythmicity of all cardiac muscle cells and are located in the wall of the right atrium near the opening of the superior vena cava. Specialized cardiac muscle cells forming the atrioventricular node are also located in the wall of the right atrium but near the interatrial wall and the opening of the coronary sinus. The left atrium contains no known nodes of pacing cells. Large specialized cardiac muscle cells are the Purkinje's cells, which make up the bundle of His. These cells are found in the subendocardial portion of the interventricular wall and conduct impulses to the ventricular myocytes of both ventricles. The aortic arch contains baroreceptors that control heart rate through a reflex arc connected to parasympathetic ganglia on the surface of the heart.

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  • 29. 

    Which of the following statements is true of cardiac development?

    • A.

      During formation of the heart loop, a single-tube heart remains suspended by a complete dorsal mesocardium (mesentery)

    • B.

      The atria are represented by cranial portions of the endocardial tubes

    • C.

      The heart bends into an S-shape because the caudal regions of the endocardial tubes grow faster than the cranial regions

    • D.

      The left and right sides of the heart result directly from the side-by-side apposition of the left and right endocardial tubes

    • E.

      The sinus venosus becomes incorporated into the atrium prior to the formation of the heart loop

    Correct Answer
    C. The heart bends into an S-shape because the caudal regions of the endocardial tubes grow faster than the cranial regions
    Explanation
    The heart forms during the third week by the apposition of left and right endocardial tubes as the head fold progresses caudally. The endocardial tubes fuse to form a single-tube heart. This fusion begins cranially in the region of the bulbus cordis (outflow trunks) and proceeds caudally through the ventricles and the atria to the sinus venosus, which is incorporated into the atrium after loop formation. Rapid proliferation of the ventricular region results in the single-tube heart bending into an S-shaped loop. During this process, the dorsal mesocardium partially breaks down, which leaves the heart suspended only at the cranial and caudal ends; the discontinuity in the mesocardium is the transverse sinus. The left and right sides of the heart are established by the subsequent division of the single-tube heart, not by the apposition of left and right endocardial tubes.

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  • 30. 

    Pain referred to the right side of the neck and extending laterally from the right clavicle to the tip of the right shoulder is most likely to involve which of the following?

    • A.

      Cervical cardiac accelerator nerves

    • B.

      Posterior vagal trunk

    • C.

      Right intercostal nerves

    • D.

      Right phrenic nerve

    • E.

      Right recurrent laryngeal nerve

    Correct Answer
    D. Right phrenic nerve
    Explanation
    The phrenic nerve, which arises from cervical nerves C3 through C5, mediates sensation from the diaphragmatic pleura and peritoneum, as well as from the pericardium; in addition, it carries motor fibers to the diaphragm. Therefore, pain from the diaphragmatic pleura or peritoneum, as well as from the parietal pericardium, may be referred to dermatomes between C3 and C5, inclusive. These dermatomes correspond to the clavicular region and the anterior and lateral neck, as well as to the anterior, lateral, and posterior aspects of the shoulder.

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  • 31. 

    An elderly woman visits the hospital emergency room with the recent onset of grotesque swelling of the right arm, neck, and face. Her right jugular vein is visibly engorged and her right brachial pulse is diminished. On the basis of these signs, her chest x-rays might show which of the following?

    • A.

      A left cervical rib

    • B.

      A mass in the upper lobe of the right lung

    • C.

      Aneurysm of the aortic arch

    • D.

      Right pneumothorax

    • E.

      Thoracic duct blockage in the posterior mediastinum

    Correct Answer
    B. A mass in the upper lobe of the right lung
    Explanation
    A Pancoast tumor in the apex of the right lung may compress the right brachiocephalic vein with resultant venous engorgement of the right arm and right side of the face and neck. In addition, there may be compression of the brachial artery, the sympathetic chain, and recurrent laryngeal nerve with attendant deficits. An aneurysm of the aortic arch could reduce pulse pressures as the great vessels are occluded, but it could not explain the venous congestion.

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  • 32. 

    A child suspected of aspirating a small, cloth-covered metal button is seen in the emergency room. Although the child does not complain of pain, there is frequent coughing. Diminished breath sounds should be heard in which of the following?

    • A.

      In both lungs

    • B.

      In the lingula of the left inferior lobe

    • C.

      In the right inferior lobe

    • D.

      In the left superior lobe

    • E.

      In the right superior lobe

    Correct Answer
    C. In the right inferior lobe
    Explanation
    Large aspirated objects tend to lodge at the carina. Smaller objects usually lodge in the right inferior lobar bronchus because the right mainstem (primary) bronchus is generally more vertical in its course than the left and of greater diameter. In addition, the takeoff angle of the right lower lobe bronchus is less acute than that of the right middle lobe, thereby nearly continuing the direction of both the right mainstem bronchus and trachea. Blockage of the airway will produce absence of breath sounds within the lobe and eventual atelectasis.

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  • 33. 

    Which of the following is a correct characterization of bronchopulmonary segments?

    • A.

      They are arranged with their bases directed toward the hilum of the lung

    • B.

      They are separated by parietal pleura

    • C.

      The arterial supply is located in the periphery of each segment

    • D.

      Each segment is supplied by a secondary or lobar bronchus

    • E.

      Veins may be used to localize the planes between segments

    Correct Answer
    E. Veins may be used to localize the planes between segments
    Explanation
    Although the segmental bronchus and artery tend to be centrally located, the veins do not accompany the arteries but tend to be located subpleurally and between bronchopulmonary segments. Indeed, at surgery the intersegmental veins are useful in defining intersegmental planes. Bronchopulmonary segments, the anatomic and functional units of the lung, are roughly pyramidal in shape, have apices directed toward the hilum of the lung, and are separated from each other by connective tissue septa. Each bronchopulmonary segment is supplied by one tertiary or segmental bronchus, along with a branch of the pulmonary artery.

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  • 34. 

    A 28-year-old woman comes into the emergency room exhibiting dyspnea and mild cyanosis, but no signs of trauma. Her chest x-ray is shown below. Which of the following is the most obvious abnormal finding in the inspiratory posteroanterior chest x-ray of this patient (viewed in the anatomic position)?

    • A.

      Bilateral expansion of the pleural cavities above the first rib

    • B.

      Grossly enlarged heart

    • C.

      Left pneumothorax (collapsed lung)

    • D.

      Paralysis of the left hemidiaphragm

    • E.

      Right hemothorax (blood in the pleural cavity)

    Correct Answer
    C. Left pneumothorax (collapsed lung)
    Explanation
    The patient has a left pneumothorax. The lucidity of the left pleural cavity with the lack of pulmonary vessels indicates that the left lung has collapsed into a small, dense mass adjacent to the mediastinum. Such a nontraumatic pneumothorax may result from the rupture of a pulmonary bleb, especially in a young person. The right lung is normal. There is no pleural fluid level indicative of hemothorax, and the near symmetry of the domes of the two hemidiaphragms on inspiration indicates normal function of the phrenic nerves. The pleural cavities normally extend superior to the first rib into the base of the neck. The heart, measuring less than one-half of the chest diameter, is of normal size.

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  • 35. 

    Which of the following forms the venous coronary sinus?

    • A.

      Left horn of the sinus venosus

    • B.

      Right horn of the sinus venosus

    • C.

      Primitive atrium

    • D.

      Bulbus cordis

    • E.

      Truncus arteriosus

    Correct Answer
    A. Left horn of the sinus venosus
    Explanation
    The sinus venosus receives the veins (cardinal) from the body. Originally the caudal end of the heart tube, the sinus venosus rotates cranially and dorsally during the looping process. The left horn of the sinus becomes a narrow channel located in the groove between the left atrium and ventricle. The coronary sinus empties into the right atrium. The right horn of the sinus forms the entrance of the two venae cavae into the right atrium and becomes the smooth-walled portion of the right atrium. The primitive atrium becomes the entire left atrium and the trabeculated (rough-walled) portion of the right atrium. The bulbus cordis gives rise to the right ventricle and the muscular portions of the outflow tracts of both ventricles. The truncus arteriosus gives rise to the vascular portions of the outflow tracts, the aorta, and the pulmonary arteries.

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  • 36. 

    . Which of the following is the last segment of the gastrointestinal tract to become fully closed into a tube and separated from the yolk sac

    • A.

      Anal canal

    • B.

      Appendix

    • C.

      Cecum

    • D.

      Ileum

    Correct Answer
    D. Ileum
    Explanation
    During the first month of development, the midgut communicates over its entirety with the yolk sac. This connection narrows during the next month to form the vitelline duct (yolk stalk, omphalomesenteric duct) as the midgut closes and usually disappears during the ninth week. Because the vitelline duct joins the ileum, this section of the gastrointestinal tract is the last to close. Failure of closure results in a persistent vitelline fistula, whereas partial obliteration results in an ileal diverticulum (of Meckel).

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  • 37. 

    A 24-year-old male visited the community clinic complaining of a draining abscess on his anterior thigh. Subsequent testing revealed an active tuberculosis infection localized in the lumbar vertebrae. The spread of infection most likely occurred via which of the following?

    • A.

      The ischiorectal fossa

    • B.

      The sheath of the psoas muscle

    • C.

      The inguinal ligament

    • D.

      A paracolic gutter

    Correct Answer
    B. The sheath of the psoas muscle
    Explanation
    Tuberculous infections of the lumbar vertebrae are frequently communicated to the sheath of the adjacent psoas muscles. Subsequently, pus may travel inferiorly over the pelvic brim and erupt on the anterior thigh near the insertion of the psoas on the lesser trochanter of the femur. Abscesses in the ischiorectal fossae may drain into the pelvis or the anal canal. The inguinal ligament passes laterally to medially superficial to the psoas muscle to transmit contents to the scrotum or labia. Its origin in the anterolateral abdominal wall is not in close approximation to the lumbar vertebrae. The paracolic gutters can spread infection or metastases into the pelvis or the subphrenic region, depending on whether the patient is erect or supine.

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  • 38. 

    . The lesser sac (omental bursa) is directly continuous with which of the following recesses or spaces?

    • A.

      Infracolic compartment

    • B.

      Left colic gutter

    • C.

      Left subphrenic recess

    • D.

      Right subphrenic space

    • E.

      Hepatorenal recess

    Correct Answer
    E. Hepatorenal recess
    Explanation
    The omental (epiploic) foramen connects the lesser sac with the hepatorenal (subhepatic) recess of the greater sac. The hepatorenal recess then communicates with the right subphrenic recess and right paracolic gutter. The subhepatic recess is perhaps the most frequently infected intra-abdominal space as a result of appendicitis, liver abscess, perforated duodenal and gastric ulcers, or perforation of the biliary tree.

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  • 39. 

    Which of the following statements concerning a direct inguinal hernia is correct?

    • A.

      It protrudes through Hesselbach's triangle

    • B.

      It is the most common type of abdominal hernia

    • C.

      It traverses the entire length of the inguinal canal

    • D.

      It contains all three fascial layers of the spermatic cord

    • E.

      It exits the inguinal canal via the superficial inguinal ring

    Correct Answer
    A. It protrudes through Hesselbach's triangle
    Explanation
    A direct inguinal hernia protrudes through a space bounded superolaterally by the inferior epigastric vessels and medially by the rectus abdominus muscle. It is found superior to the inguinal ligament in Hesselbach's triangle. The other statements are true only of an indirect inguinal hernia, which is the most common. A direct hernia traverses only the most medial part of the inguinal canal and is not covered by the most internal layers of spermatic cord fascia.

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  • 40. 

     Which of the following is unchanged during childbirth?

    • A.

      The diameter between the sacral promontory and the pubic symphysis

    • B.

      The separation between the pubic rami

    • C.

      The distance between the pubic symphysis and the tip of the coccyx

    • D.

      The width of the pelvic outlet

    Correct Answer
    A. The diameter between the sacral promontory and the pubic symphysis
    Explanation
    During childbirth, sex hormones and the release of relaxin allow loosening of several joints including the sacroiliac joints and the pubic symphysis. This, however, does not change the position of the sacral promontory relative to the pubic symphysis. Loosening of the pubic symphysis does allow the pubic rami to separate slightly, increasing the lateral diameter of the pelvis. Posterior rotation of the coccyx increases the anteroposterior dimension of the pelvic outlet.

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  • 41. 

    A 36-year-old man complained to his physician of occasional dull throbbing pain associated with the right testis and scrotum. Examination indicated varicocele of the pampiniform plexus. The physician remarked that in all probability the patient had this condition since adolescence and should not be bothered by it. The patient was emphatic that the condition had arisen within the last few months. Surgery was considered. On gaining access to the peritoneal cavity and locating the testicular vein, it was noted that the vein was inexplicably dilated. Further exploration revealed a large retroperitoneal mass in the vicinity of the lower pole of the kidney that encroached on the vein so that it did not drain freely into which of the following veins?

    • A.

      Hepatic portal vein

    • B.

      Inferior vena cava

    • C.

      Internal iliac vein

    • D.

      Right renal vein

    • E.

      Right suprarenal vein

    Correct Answer
    B. Inferior vena cava
    Explanation
    The right testicular vein normally empties into the inferior vena cava. The left testicular vein usually drains into the left renal vein. Although variations are not uncommon, the testicular veins never drain into the hepatic portal system.

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  • 42. 

    Which of the following statements correctly pertains to the dartos tunic of the scrotum?

    • A.

      It is formed by the fusion of the two layers of superficial fascia of the perineum

    • B.

      It is invested with adipose tissue

    • C.

      It participates in the cremaster reflex

    • D.

      It receives innervation from the genital branch of the genitofemoral nerve

    • E.

      It responds to cold temperatures by lowering the testes away from the body

    Correct Answer
    A. It is formed by the fusion of the two layers of superficial fascia of the perineum
    Explanation
    The two layers of superficial perineal fascia, i.e., the superficial layer of subcutaneous fascia (Cruveilhier's) and the deep layer of subcutaneous fascia (Colles'), fuse to form the dartos tunic of the scrotum. However, the superficial layer loses its fat and picks up smooth muscle. The smooth muscle of the dartos is responsive to temperature. The dartos muscle relaxes when too warm, which drops the testes away from the body, and contracts when too cool, which brings the testes closer to the body. This provides a thermoregulatory mechanism that helps maintain the optimum temperature for spermatogenesis. The cremaster reflex is associated with the spermatic cord and raises the testes within the scrotum as a protective measure. The afferent limb and efferent limbs of the cremaster reflex are provided, respectively, by the femoral and genital branches of the genitofemoral nerve.

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  • 43. 

    . At delivery, caudal analgesia is induced by administration of anesthetic into the epidural space in the sacral region. The needle is introduced via which of the following?

    • A.

      Anterior sacral foramina

    • B.

      Dural sac

    • C.

      Intervertebral foramina

    • D.

      Posterior sacral foramina

    • E.

      Sacral hiatus

    Correct Answer
    E. Sacral hiatus
    Explanation
    Caudal analgesia can be induced by injection of anesthetic through the sacral hiatus into the sacral epidural space of the vertebral canal well caudal to the termination of the dural sac. The sacral hiatus represents the absence of a complete neural arch of the fifth sacral vertebra. The four anterior and posterior sacral foramina on either side of the midline join the intervertebral foramen and provide egress for the anterior and posterior primary rami of the sacral spinal nerves. The level to which the anesthesia blocks the spinal nerves is a function of the amount delivered.

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  • 44. 

     Which of the following structures is most susceptible to unintentional damage during a hysterectomy?

    • A.

      Uterine artery

    • B.

      Ureter

    • C.

      Urinary bladder

    • D.

      Urethra

    • E.

      Kidney

    Correct Answer
    B. Ureter
    Explanation
    The uterine artery crosses anterior and superior to the ureter near the lateral fornix of the vagina. Some clinicians and anatomists used to refer to the uterine artery as "the bridge over troubled waters." Because of its close proximity to the artery, the ureter may be accidentally ligated or severed during tying off of the artery. Of course, the bladder and the kidney are large structures and should not be mistaken or unnoticed. The urethra should be far out of the operating field.

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  • 45. 

     Sympathetic and parasympathetic nerves reach the pelvic plexus by different pathways. If, during surgical resection of the rectum, the sympathetic nerves were excised bilaterally, which of the following complications would ensue?

    • A.

      A dilated and neurogenic bladder

    • B.

      Loss of control of the external urethral sphincter

    • C.

      Impotence (inability to obtain erection)

    • D.

      Inability to ejaculate

    Correct Answer
    D. Inability to ejaculate
    Explanation
    Loss of sympathetic innervation to the pelvic plexus results in an inability to ejaculate. Parasympathetic innervation in this region mediates penile erection, without which ejaculation probably cannot occur. The afferent and efferent limbs of the detrusor reflex, which controls reflex emptying of the bladder, also travel in the nervi erigentes with the parasympathetics. Thus, injury to this pathway would result in a dilated bladder. Voluntary control of the external anal sphincter and levator ani muscles is mediated through branches of the pudendal nerve.

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  • 46. 

     Which of the following statements concerning erection, emission, and ejaculation in the male is correct?

    • A.

      Contraction of the urethra is under control of the sympathetic nervous system

    • B.

      The parasympathetic nerves stimulate closure of the sphincter of the urinary bladder

    • C.

      Sympathetic neurons stimulate the helicine arteries to dilate and increase blood flow to the corpora cavernosum

    • D.

      Parasympathetic innervation stimulates emission of seminal fluid

    • E.

      Contraction of the bulbospongiosus and ischiocavernosus muscles impedes the drainage of blood from the corpora cavernosa

    Correct Answer
    E. Contraction of the bulbospongiosus and ischiocavernosus muscles impedes the drainage of blood from the corpora cavernosa
    Explanation
    The bulbospongiosus and ischiocavernosus muscles are innervated by the pudendal nerve (S2–S4). Concomitant with dilation of the helicine arteries under parasympathetic innervation, which allows blood to flow into the cavernous spaces, contraction of the bulbospongiosus and ischiocavernosus muscles at the base of the cavernous bodies prevents blood from leaving, resulting in engorgement and penile erection. Contraction of the smooth muscle of the urethra (ejaculation) is a parasympathetic function, whereas closure of the sphincter of the urinary bladder is under sympathetic control. Emission of seminal fluid and prostatic secretions is due to contraction of smooth muscle under sympathetic control.

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  • 47. 

    A 45-year-old man was riding a snowmobile and hit a snow-covered rocky outcropping. While recovering from the accident, he slipped and fell on the outcropping and now is experiencing pain in the gluteal region. In this CT scan, which of the following is the dark linear structure indicated by the arrow?

    • A.

      A fracture of the ilium

    • B.

      The sacroiliac joint

    • C.

      A spinal nerve

    • D.

      The superior gluteal artery

    • E.

      The inferior gluteal artery

    Correct Answer
    B. The sacroiliac joint
    Explanation
    The indicated line represents the sacroiliac joint. These structures are seen bilaterally between the alae of the sacrum and the ilia. The sacroiliac ligaments might have been sprained by the trauma of the fall. The pathway for spinal nerves is through foramina of the sacrum, not through long bony canals. Similarly, the pathway for the gluteal arteries is through the greater sciatic foramen between the ilium and the sacrum. However, the bones are not contiguous at that level.

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  • 48. 

    Which of the following structures is most often associated with bursitis at the shoulder?

    • A.

      Acromioclavicular joint capsule

    • B.

      Glenohumeral joint capsule

    • C.

      Subacromial bursa

    • D.

      Subdeltoid bursa

    Correct Answer
    C. Subacromial bursa
    Explanation
    Shoulder bursitis is often the result of calcium deposits associated with the subacromial bursa, which separates the acromion process from the underlying supraspinatus muscle, or within the suprajacent supraspinatus tendon. The subdeltoid bursa separates the deltoid muscle from the head of the humerus and the insertions of the rotator cuff muscles.

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  • 49. 

    The accompanying x-ray shows the shoulder of an 11-year-old female who fell off the monkey bars, extending her arm in an attempt to break her fall. The small arrows indicate a fracture in the area of the surgical neck of the humerus. The large arrows indicate which of the following?

    • A.

      A fracture at the anatomic neck of the humerus

    • B.

      The glenohumeral joint

    • C.

      The joint space between the proximal humerus and the acromion of the scapula

    • D.

      The proximal humeral epiphyseal plate

    • E.

      What is commonly called a shoulder separation

    Correct Answer
    D. The proximal humeral epiphyseal plate
    Explanation
    The large arrows indicate the proximal humeral epiphyseal plate. The young girl was only 11 and still growing. The epiphyseal plates show up on x-rays as radio-lucent cartilage and should not be confused with a fracture. The epiphysis is located at the anatomic neck of the humerus but is not discoid-shaped like many epiphyseal plates in long bones. This plate is tent-shaped, which is why it is not clearly visible all the way across the proximal humerus.

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  • 50. 

    A female patient falls on an icy sidewalk and complains of her thumb hurting. You take her x-ray and show her there are no fractures. However, she asks what the small light circles (arrow) on the x-ray are. You explain they are sesamoid bones in the tendon of the

    • A.

      Flexor pollicis longus

    • B.

      Flexor pollicis brevis

    • C.

      Adductor pollicis

    • D.

      Abductor pollicis longus

    • E.

      Abductor pollicis brevis

    Correct Answer
    B. Flexor pollicis brevis
    Explanation
    The flexor pollicis brevis has two heads and there is a sesamoid bone associated with each of the tendons of these heads. Sesamoid bones are isolated islands of bone that may occur in tendons passing over joints. The patella is the classic example. The adductor pollicis also has two heads (transverse and oblique), but they are not associated with sesamoid bones.

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  • Current Version
  • Mar 21, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Feb 04, 2010
    Quiz Created by
    Smiles
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