Reproductive System MCAT Biology Diagnostic Exam 4B Flashcards
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.
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
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.
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
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.
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
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.
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
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
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
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
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
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.
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
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)
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
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
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
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
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
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
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
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.
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
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.
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
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.
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
The renal medulla is made up primarily of:
A. glomeruli.
B. nephrons.
C. proximal tubules.
D. collecting ducts.
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
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
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
Skeletal muscle is attached to bone by:
A. cartilage.
B. ligaments.
C. tendons.
D. basement membrane.
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
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
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
