Reproductive System MCAT Biology Diagnostic Exam 4B

Question 1

Oogenesis is different from spermatogenesis in that:

A. only one ootid is generated from one oogonium.
B. only one round of cytokinesis occurs.
C. two polar bodies are secreted at the end of each telophase.
D. oocyte mitosis is more efficient than spermatocyte mitosis, leading to a regenerating pool of oogonium.

Answer 1

A. Oogonia mature into primary oocytes, which undergo meiosis I to generate a secondary oocyte and a polar body. If fertilized, the secondary oocyte undergoes meiosis II to generate an ootid (which matures into an ovum) and a second polar body (choice A is correct). Two rounds of cytokinesis are still required, one for each telophase (I and II; choice B is wrong). Each cytokinesis event generates one polar body, not two (choice C is wrong). Oocytes undergo meiosis, not mitosis. In female humans, oogonia perform mitosis in the fetal stage, to generate a lifetime supply of primary oocytes. In contrast, spermatogonia can perform mitosis through the life of a human male; this is one of the reasons females go through menopause and males do not (choice D is wrong).

Concepts tested
Reproductive Systems: Spermatogenesis Reproductive Systems: Oogenesis

Question 2

Question 2
An exercise physiologist looking at Type IIA muscle fibers under the microscope would see:

A. white cells with some mitochondria.

    B.  white cells with no mitochondria.
  	C.  red cells with many mitochondria.
  	D.  red cells with no mitochondria.

Answer 2

A. Type IIA fibers are fast twitch fibers that are moderately fatigue-resistant; so they would have mitochondria (choices B and D can be eliminated). They would not have as many mitochondria as the red (myoglobin filled) slow twitch fibers that very fatigue-resistant, and do not have myoglobin so appear white (choice C is wrong and choice A is correct).

Concepts tested
Muscular System: Skeletal Muscle Fiber Types

Question 3

During fertilization:

A. the sperm and oocyte plasma membrane fuse to form a zygote in the uterus.
B. the sperm

’

s bindin protein facilitates nuclear fusion.
C. both fast and slow blocks increase the likelihood of a second sperm fusing with the oocyte membrane.
D. the sperm must penetrate both the corona radiata and the vitelline layer.

Answer 3

D. Fertilization occurs in a fallopian tube (choice A is wrong). The sperm’s bindin protein binds an oocyte receptor to allow plasma membrane fusion and injection of the sperm nucleus (choice B is wrong). Fast and slow blocks function to decrease the likelihood of multiple sperm fusing with an oocyte (choice C is wrong). The spermatozoa must penetrate both the corona radiata (made of granulosa cells) and the zona pellucida to access the oocyte (choice D is correct).

Concepts tested
Development: Embryology/Fetal Development

Question 4

High progesterone levels right after ovulation:

A. are the result of high steroid hormone production by the chorion.
B. function to fine-tune maturation of the endometrium in preparation for implantation.

   C.  drop after high FSH levels negatively feedback to the brain.
  	D.  stimulate high estrogen production in a positive feedback loop.

Answer 4

B. Progesterone helps with endometrium development, in preparation for pregnancy (choice B is correct). It provides negative feedback to the brain, to decrease GnRH, FSH, and LH. Falling LH levels ultimately cause the corpus luteum to disintegrate, progesterone levels to drop, and menstruation to occur (choice C is wrong). Estrogen’s positive feedback loop occurs before ovulation and triggers the LH surge that causes ovulation (choice D is wrong). The chorion develops from the trophoblast of a blastocyst (developing embryo), and secretes hCG to maintain the pregnancy (choice A is wrong).

Concepts tested
Reproductive Systems: The Menstrual Cycle

Question 5

Low blood pressure and low blood volume trigger which of the following?

A. An increase in ADH followed by a subsequent decrease in aldosterone
B. An increase in ADH followed by a subsequent increase in aldosterone
C. An increase in aldosterone followed by a subsequent decrease in ADH
D. An increase in aldosterone followed by a subsequent increase in ADH

Answer 5

D. First, aldosterone levels increase (choices A and B are wrong). This allows sodium reabsorption from the distal nephron. The resulting increase in plasma osmolarity triggers antidiuretic hormone (ADH, or vasopressin) release (choice C is wrong and choice D is correct). This induces expression of water channels on the cells of the distal tubule and collecting duct, allowing water reabsorption.

Concepts tested
Renal System: Renal Regulation of Blood Pressure

Question 6

A mutation leading to a loss of function in which of the following hormones would have the greatest impact on enzyme activation in the stomach?

A. Gastrin
B. Cholecystokinin
C. Erythropoeitin
D. Secretin

Answer 6

A. Gastrin is secreted from G cells in the stomach, and stimulates acid and pepsinogen secretion, as well as increases stomach motility. Hydrochloric acid (HCl) cleaves the zymogen pepsinogen to active pepsin; a mutation leading to loss of gastrin function would impair HCl secretion and thus pepsin activation (choice A is correct). CCK (cholecystokinin) triggers release of bile and also works to regulate the flow of chyme through the pyloric sphincter and into the small intestine, but does not impact gastric enzyme activation (choice B is wrong). Erythropoeitin stimulates red blood cell production in the bone marrow and is made by the kidneys, thus it is not relevant to this question (choice C is wrong). Secretin triggers the release of pancreatic exocrine secretions (including digestive enzymes and aqueous bicarbonate) into the small intestine, and is not involved in gastric enzyme activation (choice D is wrong).

Concepts tested
Digestive System: Alimentary Canal

Question 7

What role does the macula densa (in the distal tubule) play in regulating blood pressure?

A. High filtrate osmolarity triggers the macula densa to stimulate the JG cells and dilate the afferent arterioles.
B. Low filtrate osmolarity triggers the macula densa to stimulate the JG cells and dilate the afferent arterioles.

    C.  High filtrate osmolarity triggers the macula densa to stimulate the JG cells and constrict the afferent arterioles.
  	D.  Low filtrate osmolarity triggers the macula densa to stimulate the JG cells and constrict the afferent arterioles.

Answer 7

B. The macula densa on the distal convoluted tubule monitors filtrate osmolarity. If the filtrate osmolarity decreases (choices A and C are wrong), this indicates a drop in filtration rate. The macula densa then stimulates the juxtaglomerular cells (in order to activate the renin-angiotensin axis to increase blood pressure), while also causing the afferent arterioles to dilate (choice D is wrong and choice B is correct). The combination of increased systemic blood pressure and increased blood flow to the glomerulus increases filtration rate.

Concepts tested
Renal System: Renal Regulation of Blood Pressure

Question 8

Which of the following is an incorrect matching of developmental phase and characteristics?

A. Blastulation – development of the blastocyst, including the trophoblast and the outer cell mass
B. Differentiation – the ectoderm develops into neural tissue, while the endoderm develops into epithelial tissue
C. Cleavage – cell divisions without an increase in cell volume, resulting in the morula
D. Gastrulation – development of the three primary germ layers (ectoderm, endoderm and mesoderm)

Answer 8

A. The ectoderm differentiates to form all nervous system tissue, and most epithelial components are derived from the endoderm (choice B is a correct match and can be eliminated). Cleavage is the development of the morula from the zygote (choice C is a correct match and can be eliminated). Gastrulation is germ layer development (choice D is a correct match and can be eliminated). However, blastulation is the development of the blastocyst, which is composed of the trophoblast and an inner cell mass (choice A is an incorrect match and the correct answer choice).

Concepts tested
Development: Embryology/Fetal Development

Question 9

Which of the following types of renal vasculature are NOT responsible for returning components to the circulatory system as part of filtrate adjustment?

A. Efferent arterioles
B. Afferent arterioles
C. Peritubular capillaries
D. Vasa recta

Answer 9

B. The afferent arterioles carry blood toward the glomerulus, but do not function in returning substances to the circulatory system after filtration (choice B is the correct answer). The efferent arterioles carry blood away from the glomerulus and ultimately branch into the peritubular capillaries. These vessels interlace with the nephron and pick up reabsorbed material (choices A and C return components to the circulatory system and can be eliminated). The vasa recta is part of the peritubular capillaries; it runs in parallel with the renal tubule and is also involved in returning material to the circulatory system (choice D can be eliminated).

Concepts tested
Renal System: Nephron Structure/Function

Question 10

Which of the following statements about bile is/are true?

I. Bile emulsifies lipids for easier digestion.

II. The amphipathic nature of bile allows it to digest lipids.

III. Bile is produced by the liver and gallbladder.

A. I only
B. I and III only
C. II and III only
D. I, II, and III

Answer 10

A. Item I is true: bile is amphipathic (has both polar and non-polar regions); this allows it to interact with both lipids and the hydrophilic intestinal contents. The lipids are emulsified, allowing pancreatic lipases easier access to them for digestion. Bile is sometimes referred to as intestinal soap, because it emulsifies fat in the intestines much like soap emulsifies fat on your hands when you wash them (choice C can be eliminated). Item II is false: bile is not an enzyme and does not digest lipids. It only makes it easier for the pancreatic enzymes to digest (choice D can be eliminated). Item III is false: bile is made only by the liver. It is stored and concentrated in the gallbladder (choice B can be eliminated and choice A is correct).

Concepts tested
Digestive System: Accessory Organs

Question 11

Which of the following is the best description of fibrous cartilage?

A. Provides a dynamic balance of support and flexibility
B. Provides rigid, strong support
C. Provides less support but more flexibility
D. Eventually ossifies and becomes bone

Answer 11

B. Fibrous cartilage is the strongest and least flexible type of cartilage and it is found in places like the intervertebral disks as well as the pubic symphysis (choice B is correct). However, it does not eventually ossify; this would create a completely rigid structure whereas the cartilage does provide a little bit of flexibility (imagine if your spine was complete bone, choice D is wrong). Elastic cartilage provides the most flexibility (choice C is wrong) and is found in places like the outer ear and the epiglottis. Hyaline cartilage balances support with flexibility (choice A is wrong) and is found on the ends of bones, at the joints. It is also known as articular cartilage.

Concepts tested
Skeletal System: Connective Tissue/Bone

Question 12

All of the following are true statements EXCEPT:

A. fraternal twins occur from the fertilization of both oocytes of a double ovulation; one that occurs about midcycle (day 14) and one that occurs about a week later.
B. ovulation is triggered by an LH surge that is the result of the positive feedback of estrogen on the anterior pituitary gland.
C. LH causes ovulation and the formation of the corpus luteum.
D. menstruation is triggered by a drop in estrogen and progesterone levels.

Answer 12

A. Fertilization of both oocytes from a double ovulation is in fact what leads to fraternal twins, however the two ovulations must occur within 24 hours of each other, not a week apart (choice A is not true and is the correct answer choice). The LH surge that causes ovulation is the result of the positive feedback effect that estrogen has at high levels (choice B is true and can be eliminated), and the LH surge causes both ovulation and the formation of the corpus luteum after ovulation (choice C is true and can be eliminated). The drop in estrogen and progesterone as the corpus luteum degenerates (around day 27-28) is what triggers menstruation (choice D is true and can be eliminated).

Concepts tested
Reproductive Systems: The Menstrual Cycle

Question 13

A block in prophase II of spermatogenesis would result in:

A. limited numbers of spermatids.
B. a decreased population of secondary spermatocytes.
C. an accumulation of primary spermatocytes.
D. increased gamete migration from the seminiferous tubule basement membrane to its lumen.

Answer 13

A. A block in prophase II of spermatogenesis would mean that the secondary spermatocytes could not complete meiosis II and would accumulate (choice B is wrong). This would lead to fewer spermatids (choice A is correct). Since spermatogenesis would be decreased, there would be less gamete migration from the seminiferous tubule basement membrane to its lumen (choice D is wrong). Finally, primary spermatocytes are the cells going through meiosis I, not meiosis II. Since the block is in meiosis II (i.e. after the primary spermatocytes have become secondary spermatocytes), the number of primary spermatocytes should be unaffected (choice C is wrong).

Concepts tested
Reproductive Systems: Spermatogenesis

Question 14

During puberty and sexual maturation, what impact do androgens and estrogens have on the epiphyseal plate?

A. The hormones ossify the epiphyseal plate, thus stopping growth.
B. The hormones ossify the epiphyseal plate, thus creating a layer of cartilage within the bone.
C. The hormones stimulate the epiphyseal plate to produce collagen and thus lengthen the bone.
D. The hormones stimulate the epiphyseal plate to produce cartilage and thus lengthen the bone.

Answer 14

A. Androgens and estrogens aid in the eventual ossification of the epiphyseal plate, which stops further growth and results in a person reaching his/her final height (choices C and D are wrong). This ossification does not result in a layer of cartilage being formed as mature bones are composed of collagen and hydroxyapatite, a calcium-phosphate crystalline solid (choice B is wrong and choice A is correct).

Concepts tested
Skeletal System: Bone Structure/Turnover

Question 15

The renal medulla is made up primarily of:

A. glomeruli.
B. nephrons.
C. proximal tubules.
D. collecting ducts.

Answer 15

D. The renal medulla is divided into regions called pyramids, which are composed of collecting ducts (choice D is correct). Glomeruli are the beginning of the nephron, where filtration occurs, and proximal tubules are found directly after glomeruli; both are located in the renal cortex (choices A and C are wrong). While portions of the nephron are found in the renal medulla, “nephron” is a broad term and not the best answer choice here (choice D is better than choice B).

Concepts tested
Renal System: Nephron Structure/Function

Question 16

Which of the following does NOT describe the esophagus?

A. The opening of the esophagus is protected by the epiglottis.
B. The upper esophagus is composed of skeletal muscle.
C. Peristalsis begins in the esophagus.
D. The esophagus is separated from the stomach by the cardiac sphincter

Answer 16

A. The trachea (not the esophagus) is protected by the epiglottis, as it prevents food or liquids from entering the lungs when swallowing (choice A does not describe the esophagus and is the correct answer choice). The upper portion of the esophagus is made of skeletal muscle so that swallowing can be initiated voluntarily (choice B describes the esophagus and can be eliminated), but this merges quickly into smooth muscle, which provides the peristalsis to move the bolus down to the stomach (choice C describes the esophagus and can be eliminated). The cardiac sphincter separates the esophagus and the stomach (choice D describes the esophagus and can be eliminated).

Concepts tested
Digestive System: Alimentary Canal

Question 17

Skeletal muscle is attached to bone by:

A. cartilage.
B. ligaments.
C. tendons.
D. basement membrane.

Answer 17

C. Tendons are the bands of collagen-based connective tissue which link skeletal muscle to bone (choice C is correct). Cartilage is part of joints (covers the ends of bones) as well as a filler tissue in places like the nose, but it is not involved in the attachment of skeletal muscle to bone (choice A is wrong). Ligaments link bone to bone (choice B is wrong) and basement membranes support layers of epithelial cells, such as the intestinal lining or skin (choice D is wrong).

Concepts tested
Skeletal System: Connective Tissue/Bone

Question 18

A patient with bulimia begins to develop lethargy which is believed to be related to metabolic alkalosis. Which of the following best explains this finding?

A. AA decrease in the cooperativity of oxygen binding to hemoglobin
B. An increase in oxygen delivery due to hemoglobin’s decreased oxygen affinity
C. A right-shift in the oxygen saturation curve for hemoglobin
D. A left-shift in the oxygen saturation curve for hemoglobin

Answer 18

D. Repeated vomiting can raise blood pH (metabolic alkalosis) and increase hemoglobin’s affinity for oxygen (choice B is wrong). This is seen as a left-shift in the oxygen saturation curve for hemoglobin (choice D is correct and choice C is wrong). Note that answer choices B and C describe decreased oxygen affinity which may be due to situations such as acidosis, increased temperature, or increased CO2. Cooperativity does not change significantly with the shift described by the Bohr effect; the curve would still be sigmoidal (choice A is wrong).

Concepts tested
Cardiovascular System: Blood Digestive System: Alimentary Canal

Question 19

All of the following are true of the bacteria living in the large intestine EXCEPT:

A. the bacteria compete with consumed pathogens that have evaded other innate immune system defenses.
B. the bacteria are mostly aerobic with some facultative anaerobes.
C. the bacteria produce vitamin K, which is necessary for proper blood clotting.
D. the bacteria are considered to be mutualistic symbionts because the human host derives benefit while the bacteria obtain a steady source of food in the form of undigested material passing through the gut.

Answer 19

B. The gastrointestinal tract has a limited supply of oxygen within it, especially once the large intestine is reached. Bacteria residing there must be facultative or obligate anaerobes (choice B does not describe the bacteria in the gut and is the correct answer choice). The bacteria compete with pathogens, providing an additional immune mechanism (choice A is true and can be is eliminated) and also produce vitamin K, which is involved in blood clotting (choice B is true and can be eliminated). The fact that both humans and bacteria benefit from this arrangement makes this a mutualistic relationship (choice D is true and can be eliminated).

Concepts tested
Digestive System: Alimentary Canal

Question 20

What two components are unique to the regulation of smooth muscle?

A. Myosin light chain kinase and troponin
B. Troponin and tropomyosin
C. Tropomyosin and calmodulin
D. Calmodulin and myosin light chain kinas

Answer 20

D. Troponin and tropomyosin are the regulatory proteins used in cardiac and skeletal muscle, but not smooth muscle (choices A, B, and C are wrong). In smooth muscle, calcium binds to calmodulin, activating myosin light chain kinase (MLCK), which then phosphorylates the myosin light chain. This phosphorylation permits interaction between actin and myosin, triggering contraction (choice D is correct).

Concepts tested
Muscular System: Cardiac and Smooth Muscle

Question 21

Question 21
Bone tissue can be compact or spongy. Which of the following is found in spongy bone but NOT in compact bone?

A. Osteons
B. Osteocytes
C. Red bone marrow
D. Blood vessels

Answer 21

C. Red bone marrow is the tissue where blood cell production takes place and is found only in spongy bone. Osteons are the long cylinders of bone that make up compact bone tissue and are not found in spongy bone (choice A can be eliminated). Osteocytes are mature bone cells and are found in both spongy and compact bone (choice B can be eliminated), and blood vessels are found in both spongy and compact bone (choice D can be eliminated).

Concepts tested
Skeletal System: Bone Structure/Turnover

Question 22

Which of the following explains why incompatible fetal blood type does not induce an immune response in a pregnant female, but a HIV-positive woman can pass the disease on to her new baby?

A. The placenta is a complex capillary network that allows many maternal blood components to pass into fetal circulation, but only waste products to pass into maternal circulation.
B. The fetus receives half its genomic information from each parent, but mitochondrial genetic material is inherited solely from the mother.
C. Fertilization occurs in the fallopian tube and the embryo can be exposed to maternal factors during migration to the uterus.
D. The chorion is specific and limiting in terms of which factors can pass into the maternal or fetal circulatory systems.

Answer 22

A. Many maternal blood components, such as oxygen, nutrients, some antibodies, some drugs and toxins, and some viruses, can pass from the maternal blood supply into the developing fetus. In contrast, few molecules can pass from fetal blood into maternal circulation (choice A is correct). While choice B is an accurate statement, it does not answer the question (choice B can be eliminated). Fertilization does occur in the fallopian tubes, but this does not explain the differential exchange between fetus and mother (choice C can be eliminated). The chorion secretes hCG and other hormones in the first trimester, and ultimately becomes the placenta, but again, this does not explain the fact that more things can pass from mother to baby than from baby to mother (choice D can be eliminated).

Concepts tested
Reproductive Systems: Female Reproductive System

Question 23

Which route describes how filtrate moves through the nephron?

A. Loop of Henle, PCT, glomerulus, DCT
B. Glomerulus, PCT, DCT, loop of Henle
C. Loop of Henle, glomerulus, PCT, DCT
D. Glomerulus, PCT, loop of Henle, DCT

Answer 23

D. The filtrate is first formed in Bowman’s capsule, as components of blood pass from the glomerular capillaries through the glomerular basement membrane (choices A and C are wrong). The filtrate then enters the renal tubule, the first portion of which is the proximal convoluted tubule (PCT). From the PCT, the filtrate moves through the loop of Henle, and finally the distal convoluted tubule (DCT, choice B is wrong and choice D is correct).

Concepts tested
Renal System: Nephron Structure/Function

Question 24

A patient has suffered nerve damage which has impaired the contraction of his scalene muscles and results in difficulty breathing. Which of the following is most likely to be affected?

A. Chest wall elasticity
B. Diaphragm function
C. Inspiration
D. Passive expiration

Answer 24

C. This question is essentially asking what function the scalene muscles play in respiration and, as you are not required to know this function, is best answered by process of elimination. The elasticity of the chest wall, which is partially responsible for preventing collapse of the lungs, is a function primarily of bone and other connective tissue, and not any particular muscle group (choice A can be eliminated). Passive expiration is a passive process and no muscle contraction is required (choice D can be eliminated), and there is no reason to believe the function of the diaphragm will be directly affected by the impaired function of the scalene muscles (choice B can be eliminated). This leaves choice C: the scalene muscles, in addition to the sternocleidomastoid and others, are involved in inspiration (choice C is correct).

Concepts tested
Respiratory System: Ventilation and pH Regulation

Question 25

The Mullerian ducts in females:

A. develop into the ovary and fetal mammary tissue.
B. regress and the Wolffian ducts develop into female internal genitalia.
C. develop into internal genitalia such as the fallopian tubes, uterus, and cervix.
D. regress and the Wolffian ducts develop into female external genitalia.

Answer 25

C. The Wolffian ducts regress in females (choice B and D are wrong), and the Mullerian ducts develop into female internal genitalia, such as the fallopian tubes, uterus, and cervix (choice C is correct). Note that mammary glands develop mostly from the ectoderm, because they are similar to glands found in skin (choice A is wrong).

Concepts tested
Reproductive Systems: Female Reproductive System

Question 26

The male reproductive system includes accessory glands, gonads and other genital structures (both internal and external). Which of the following is true?

A. Semen must pass through the urethra, then the ductus deferens on its way out of the body.
B. The testes contains the seminiferous tubules and bulbourethral glands, and the scrotum aids in temperature control.
C. Accessory organs such as the seminal vesicles and prostate help with semen production.
D. In addition to helping with ejaculation, the urethra also functions in urine and solid waste excretion.

Answer 26

C. Many components of semen are generated by the accessory glands (bulbourethral glands, seminal vesicles, and prostate; choice C is correct). Sperm are made in the seminiferous tubules of the testes, mature in the epididymis and are stored in the vas deferens (or ductus deferens). During ejaculation, they travel with the rest of semen through the ejaculatory duct and then the urethra (choice A is wrong). The testes contain the seminiferous tubules and the epididymis, but not the bulbourethral glands (choice B is wrong). While the urethra does function in urination, it plays no role in solid waste (feces) excretion (choice D is wrong).

Concepts tested
Reproductive Systems: Male Reproductive System

Question 27

What best characterizes alveolar ducts, which follow the respiratory bronchioles?

A. They are the terminal component of the respiratory zone.
B. They are the area with greatest gas exchange in the lung.
C. They are the first component of the respiratory zone.
D. They are thin-walled branches of the respiratory zone where gas exchange can occur.

Answer 27

D. The alveolar ducts are a portion of the respiratory zone where gas exchange occurs (choice D is correct). They branch further out into individual alveoli where the vast majority (approximately 90%) of gas exchange occurs (choices A and B are wrong). The respiratory zone is composed of the respiratory bronchioles, alveolar ducts, and alveoli (choice C is wrong).

Concepts tested
Respiratory System: Conduction and Respiratory Zones

Question 28

At what stage of the sliding filament cycle is ATP hydrolyzed?

A. Resetting the myosin head to bind actin again
B. Release of actin
C. Binding of the myosin head to actin
D. During the power stroke

Answer 28

A. ATP is hydrolyzed into ADP and Pi when the myosin-heads are reset to their high-energy conformation (choice A is correct). The myosin heads are now ready to bind actin; ATP has already been hydrolyzed and ADP is bound to myosin (choice C is wrong). The power stroke occurs when myosin (now bound to actin) returns to its low-energy conformation; no ATP is needed to do this (choice D is wrong). ATP binding (but not hydrolysis) is required in order to release actin from the myosin heads and start the cycle over (choice B is wrong).

Concepts tested
Muscular System: Sliding Filament Theory/Excitation-Contraction Coupling

Question 29

Pemphigus vulgaris results from autoantibodies directed against a protein found between keratinocytes (skin cells). Which skin layer would you expect to be involved in the blisters seen in these patients?

A. Epidermis
B. Dermis
C. Hypodermis
D. Subcutaneous tissue

Answer 29

A. The outermost layer of the skin is the epidermis, made up primarily of cells called keratinocytes (choice A is correct). The dermis is beneath the epidermis and contains collagen and elastic fibers which help support the skin (choice B is wrong). The hypodermis, also known as the subcutaneous tissue, is primarily fat (choices C and D are wrong).

Concepts tested
Skin: Layers

Question 30

Urine formation begins with filtration of the blood, after which the filtrate is modified via reabsorption and secretion as it travels along the nephron. Water, ions, and small hydrophilic molecules are all filtered into the nephron. Which of the following provides the best description of the composition of urine in a healthy individual?

A. Water, ions, urea, glucose
B. Water, ions, urea
C. Water, proteins, ions, urea
D. Water, urea, proteins, glucose

Answer 30

B. Water, ions, urea, and glucose are all small enough and hydrophilic enough to be filtered into the nephron at the glomerulus. However, glucose is completely reabsorbed into the blood by a healthy individual, so urine does not contain glucose (choice A is wrong). Proteins are too large to be filtered and so never enter the nephron (choices C and D are wrong).

Concepts tested
Renal System: Nephron Structure/Function

Question 31

In premature deliveries before 30 weeks gestation, pulmonary surfactant has not yet been produced. What difficulties would be expected in these infants?

A. Decreased CO2 exchange resulting in respiratory alkalosis
B. Decreased O2 exchange resulting in respiratory alkalosis
C. Collapse of smaller airways resulting in respiratory acidosis
D. Collapse of bronchi resulting in respiratory acidosis

Answer 31

C. Without surfactant, the smaller airways (alveolar ducts/alveoli) collapse and are held together by the surface tension of water. This results in reduced oxygen and carbon dioxide exchange, which leads to respiratory acidosis (choices A and B can be eliminated and choice C is correct). Larger airways, such as bronchi, are structurally supported by connective tissue and are much less likely to collapse (choice D is wrong).

Concepts tested
Respiratory System: Conduction and Respiratory Zones Respiratory System: Ventilation and pH Regulation

Question 32

How are peptidases activated in the duodenum?

A. Trypsinogen from the pancreas is converted to trypsin by stomach acid; trypsin then activates the other pancreatic enzymes.
B. Enterokinase converts trypsinogen from the pancreas into trypsin; trypsin then triggers the release of other pancreatic enzymes.
C. Enterokinase converts trypsinogen from the pancreas into trypsin; trypsin then activates the other pancreatic enzymes.
D. Trypsinogen from the pancreas is converted to trypsin by stomach acid; trypsin then activates the brush border enzyme enterokinase.

Answer 32

C. The majority of peptidases in the duodenum come from the pancreas and are secreted as zymogens. Because they work in the duodenum they must be activated there, so stomach acid can’t really play a role (choices A and D are wrong). Enterokinase, a duodenal enzyme, cleaves and activates the pancreatic zymogen trypsinogen; the active enzyme trypsin then cleaves other pancreatic zymogens to activate them (choice C is correct). The release of pancreatic enzymes is triggered primarily by secretin (a duodenal hormone); cholecystokinin (another duodenal hormone) can also help (choice B is wrong).

Concepts tested
Digestive System: Digestive Enzymes

Question 33

How do troponin and tropomyosin work to regulate skeletal muscle contraction?

A. Globular troponin binds calcium, a conformational change in protein pulls filamentous tropomyosin, and actin binding sites on myosin are exposed.
B. Globular troponin binds calcium, a conformational change in protein pulls filamentous tropomyosin, and myosin binding sites on actin are exposed.
C. Filamentous tropomyosin binds calcium, a conformational change in protein pulls globular troponin, and actin binding sites on myosin are exposed.
D. Filamentous tropomyosin binds calcium, a conformational change in protein pulls globular troponin, and myosin binding sites on actin are exposed.

Answer 33

B. Troponin is the regulatory protein that binds calcium (choices C and D are wrong). This induces a conformational change in troponin that pulls on tropomyosin in order to expose the myosin binding sites on actin. This allows interaction of actin and myosin, and contraction, to occur (choice A is wrong and choice B is correct).

Concepts tested
Muscular System: Sliding Filament Theory/Excitation-Contraction Coupling

Question 34

Which of the following describes the path of travel for sperm in the female reproductive tract?

A. Ovary, fallopian tube, uterus, birth canal
B. Vagina, ovary, fallopian tube, uterus
C. Cervix, uterus, vagina, fallopian tube
D. Vagina, cervix, uterus, fallopian tube

Answer 34

D. Sperm are ejaculated into the female vagina (choice C is wrong), swim through the cervix into the uterus, and travel through a fallopian tube to an oocyte (choice D is correct). Sperm never enter the ovary (choices A and B are wrong). Note that choice A describes the path of a fetus during the birthing process.

Concepts tested
Reproductive Systems: Female Reproductive System

Question 35

What allows for a similarity in how cardiac muscle and smooth muscle transmit action potentials from cell to cell?

A. Presence of tight junctions
B. Presence of gap junctions
C. Presence of voltage-gated sodium channels
D. Presence of desmosomes

Answer 35

B. Both cardiac and smooth muscle transmit action potentials directly from cell to cell. This can be accomplished because the cells are connected via gap junctions (choice B is correct). Tight junctions would preclude action potential transmission (choice A is wrong) as would desmosomes (choice D is wrong). Voltage-gated sodium channels are important for the rapid depolarization seen in muscle cell action potentials, but does not contribute to the transmission of action potentials between cells (choice C is wrong).

Concepts tested
Muscular System: Cardiac and Smooth Muscle

Question 36

A toddler aspirates a toy car and is rushed to the emergency room to have it removed. What are the most likely blood gas findings?

A. Increased O2, increased CO2
B. Increased O2, decreased CO2
C. Decreased O2, increased CO2
D. Decreased O2, decreased CO2

Answer 36

C. After aspirating the toy car, a portion of the lung (or the entire lung) being supplied by that bronchus will no longer participate in gas exchange. This results in a smaller quantity of oxygen being absorbed (decreasing blood oxygen levels, choices A and B can be eliminated) and an increased quantity of carbon dioxide accumulating (choice D can be eliminated and choice C is correct).

Concepts tested
Respiratory System: Ventilation and pH Regulation

Question 37

All of the following are types of dense connective tissue EXCEPT:

A. adipose tissue.
B. bones.
C. ligaments.
D. tendons.

Answer 37

A. Connective tissues are classified as “loose” or “dense” based on the amount of collagen they contain; those with a lot of collagen are dense tissues, and tend to play more supportive roles. Bones, tendons (which connect muscles to bone), and ligaments (which connect bones to other bones), are all types of dense connective tissue (choices B, C, and D can be eliminated). Adipose tissue, or fat, contains virtually no collagen and is a type of loose connective tissue (choice A is wrong and is the correct answer choice).

Concepts tested
Skeletal System: Connective Tissue/Bone

Question 38

Severe burns that cover a large portion of the body present several significant risks. Which of the following is one of the largest risks to a patient suffering from severe burns?

A. Metabolic acidosis
B. Overhydration due to inability to sweat
C. Hypothermia due to inability to sweat
D. Infection

Answer 38

D. With severe burns, many of the normal functions of skin are disrupted. Without the skin functioning as a nonspecific barrier to bacteria and other pathogens, infection is a major concern (choice D is correct). (Note that the other major concern is dehydration, but this is not listed as an answer choice.) Sweating is not a normal means of eliminating excess water (choice B is wrong) and while sweating is important to help prevent overheating, hypothermia (a drop in body temperature) would not be prevented by sweating (choice C is wrong). The skin does not play a significant role in pH regulation (choice A is wrong).

Concepts tested
Skin: Thermoregulation

Question 39

Which of the following best describes the transmission of an action potential through a skeletal muscle cell based on stimulation from the neuromuscular junction (NMJ)?

A. ACh released at the neuromuscular junction triggers an end plate potential, threshold is reached, sarcoplasmic reticulum is depolarized, action potential travels along transverse tubules
B. NE released at the neuromuscular junction triggers an end plate potential, threshold is reached, sarcoplasmic reticulum is depolarized, action potential travels along transverse tubules
C. ACh released at the neuromuscular junction triggers an end plate potential, threshold is reached, action potential travels along transverse tubules, sarcoplasmic reticulum is depolarized
D. NE released at the neuromuscular junction triggers an end plate potential, threshold is reached, action potential travels along transverse tubules, sarcoplasmic reticulum is depolarized

Answer 39

C. The release of acetylcholine (ACh) into the NMJ must first depolarize the cell to create an end plate potential (EPP, choices B and D are wrong). The EPP must be sufficient to reach the threshold of the cell, causing an action potential to fire. The action potential then travels along the plasma membrane of the muscle cell, and into the interior of the cell via the transverse (T) tubules where it depolarizes the sarcoplasmic reticulum (choice A is wrong and choice C is correct). Depolarization of the SR allows the release of calcium into the cytoplasm so that contraction can occur.

Concepts tested
Muscular System: Skeletal Muscle Structure and Sarcomeres

Question 40

An exercise physiologist performs an in vitro assay to analyze the Bohr effect in a system where the bicarbonate in the blood has been replaced by a synthetic buffer. Following the addition of acetazolamide (a carbonic anhydrase inhibitor), he increased the partial pressure of carbon dioxide in this model system two-fold. Which of the following changes would be expected immediately?

A. A right-shift in the oxygen saturation curve for hemoglobin
B. A left-shift in the oxygen saturation curve for hemoglobin
C. Hemoglobin is insensitive to pH change
D. No significant shift in the oxygen saturation curve

Answer 40

D. The normal buffer of blood, bicarbonate, has been removed and carbonic anhydrase, which facilitates the reaction of carbon dioxide and water to form carbonic acid, has been inhibited. This results in blood pH being independent of carbon dioxide concentration (choices A and B are not correct) and no significant shift in the hemoglobin saturation curve would take place (choice D is correct). If the pH of the synthetic blood was changed, we would still observe the expected shifts in the hemoglobin/oxygen saturation curve as no changes in hemoglobin were made in this setup (choice C is not correct).

Concepts tested
Cardiovascular System: Blood

Question 41

Multipotent cells can become

A. all cell types in the body, but not the trophoblast.
B. some, but not all, cell types in the body.
C. all cell types in the body, including the trophoblast.
D. one specific cell type in the body.

Answer 41

B. Multipotent cells can become some, but not all cell types in the body. The cells of the three primary germ layers are considered multipotent; for example, some cells in the mesoderm could become muscle, but not skin or bone (choice B is correct). Totipotent cells, like the zygote or morula, can become any cell type in the body (choice A is wrong), including the trophoblast (choice C is wrong). Specialized (determined) cells can only become one cell type in the body (choice D is wrong).

Concepts tested
Development: Stem Cells

Question 42

The function of the loop of Henle is to:

A. create a concentration gradient in the medulla to facilitate the reabsorption of water at the collecting duct.
B. reabsorb ions such as sodium and calcium under the control of various hormones.
C. reabsorb water under the control of ADH.
D. selectively reabsorb potassium and sodium to allow the reabsorption of water and urine concentration.

Answer 42

A. The loop of Henle establishes a concentration gradient in the medulla, so that as the collecting duct passes through it, water can be reabsorbed (thus concentrating the urine; choice A is correct). ADH makes the collecting duct permeable to water, facilitating this reabsorption (choice C is wrong), but if the gradient did not exist, there would be no driving force for the movement of water out of the collecting duct. The selective reabsorption of ions under the control of hormones takes place at the distal convoluted tubule (DCT). For example, this is where aldosterone and parathyroid hormone have their effect (choice B is wrong). Only sodium is selectively reabsorbed by the loop of Henle. Potassium in general is secreted into the urine (choice D is wrong).

Concepts tested
Renal System: Nephron Structure/Function

Question 43

Osteoclasts are inhibited as part of bone remodeling by which hormone?

A. Calcitriol
B. Parathyroid hormone
C. Cortisol
D. Calcitonin

Answer 43

D. Parathyroid hormone and calcitriol are involved in stimulating the osteoclasts to phagocytically destroy bone, thus freeing up calcium to be transported by the bloodstream to other parts of the body, and also promoting the absorption of calcium from the gut (choices A and B are wrong). Cortisol is a stress hormone and can actually increase osteoclast function (choice C is wrong). Calcitonin inhibits osteoclasts resulting in net bone production during remodeling (choice D is correct).

Concepts tested
Skeletal System: Bone Structure/Turnover

Question 44

Which of the following is a FALSE statement about the birthing process?

A. Cervical dilation is the first stage of labor.
B. Uterine and abdominal smooth muscle contractions help push the baby through the birth canal.
C. The placenta is delivered after the baby, in the third stage of labor.
D. Uterine contractions minimize bleeding and prolactin promotes milk production after the baby is born.

Answer 44

B. Choices A, C and D are accurate statements and can be eliminated. Smooth muscle contractions of the uterus and abdominal skeletal muscle contractions help push the baby out (choice B is false and the correct answer choice).

Concepts tested
Reproductive Systems: Female Reproductive System

Question 45

The primary function of fructose and buffers in semen is to help spermatozoa survive the path from the:

A. vas deferens to the fallopian tube, by providing nutrients and pH regulation.
B. seminiferous tubules to the fallopian tube, by providing nutrients and lubrication.
C. epididymis to the fallopian tube, by providing nutrients and temperature control.
D. sustenacular cells to the fallopian tube, by providing lubrication and pH regulation.

Answer 45

A. Spermatids are made in the seminiferous tubules of the testes, mature in the epididymis and are stored as spermatozoa in the vas deferens until ejaculation. Fructose in the semen provides nutrients, and alkaline secretions help neutralize the low pH in the male urethra (from urine passing through) and the female vagina (which functions as part of the innate immune system, similar to the low pH in the stomach). Overall, the best answer choice is A. Neither component provides lubrication (choices B and D are wrong) and temperature control is a function of the scrotum (choice C is wrong).

Concepts tested
Reproductive Systems: Male Reproductive System