Reproduction and Development

During puberty and sexual maturation, what impact do androgens and estrogens have on the epiphyseal plate? Question 10 Answer Choices 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).

What stage(s) of sexual response is/are mediated by the sympathetic nervous system? Question 2 Answer Choices A. Orgasm and resolution B. Arousal only C. Arousal and orgasm D. Orgasm only

A. Orgasm and resolution

High progesterone levels right after ovulation: Question 4 Answer Choices 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).

Babies born prematurely (between 28-32 weeks of gestation) typically suffer from IRDS, infant respiratory distress syndrome. IRDS is characterized by difficulty in breathing, extreme exhaustion, and sometimes death, and is due to a lack of surfactant. When during the fetal stage is surfactant produced in significant quantities? Question 10 Answer Choices A. 30 weeks B. 28 weeks C. 33 weeks D. 20 weeks

C. Surfactant is produced in significant quantities by about 33 weeks of gestation. Prior to then, surfactant is limited and babies born earlier than 33 weeks typically suffer from IRDS.

At birth, females possess the total number of their potential ova. In oogenesis, meiotic division is arrested for a long period at which stage? Question 15 Answer Choices A. Secondary oocyte B. Primary oocyte C. Oogonium D. Ovum

B. At birth, females possess the total number of their potential ova. In oogenesis, meiotic division is arrested for a long period at the primary oocyte stage. Primary oocytes are arrested in meiotic prophase I in the ovaries from birth until they are stimulated to ovulate sometime during sexual maturity.

The primary follicle includes each of the following EXCEPT: Question 14 Answer Choices A. the zona pellucida. B. the second polar body C. thecal cells. D. granulosa cells.

B. The primary follicle does NOT include the second polar body. The primary follicle includes a primary oocyte and, moving outward from the egg surface, a zona pellucida, granulosa cells, and thecal cells (making these all incorrect answer choices). The second polar body is formed after completion of the second meiotic division, only after fertilization and much later than when the primary follicle is present (making this the correct answer).

Which of the following is the best description of fibrous cartilage? Question 12 Answer Choices 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.

At what stage of embryonic development are all three germ layers established? Question 6 Answer Choices A. Blastula B. Gastrula C. Embryo D. Zygote

B. Gastrula

Which hormone is most responsible for ovulation? Question 4 Answer Choices A. Progesterone B. Luteinizing hormone C. Follicle stimulating hormone D. Estrogen

B. Luteinizing hormone

Multipotent cells can become Question 41 Answer Choices 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.

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).

How is the final phenotype of a developing stem cell established? Question 9 Answer Choices A. Differentiation employs methylation to create the genetic identity of the cell. B. Determination allows for phenotypic expression of alternative genomic splicing. C. Its genetic fate is determined and then it becomes visibly differentiated D. Its genetic fate is differentiated and then it becomes visibly determined.

C. A developing stem cell's genetic fate is determined and then it becomes visibly differentiated to establish its final phenotype. Stem cells need to have their genetic programming fixed first via the process of determination. This genetic programming is then physically manifested through the process of differentiation.

Which of the following is NOT under control of the sympathetic nervous system in a male? Question 12 Answer Choices A. Emission of sperm and semen through the urethra B. Ejaculation of sperm and semen C. Dilation of arteries in the erectile tissue D. Resolution, or constriction of arteries in the erectile tissue

C. Dilation of arteries in the erectile tissue is NOT under control of the sympathetic nervous system in a male. Only the first phase of the male sexual act, arousal, is under control of the parasympathetic nervous system. This includes dilation of arteries in the erectile tissue ("Dilation of arteries in the erectile tissue" is not controlled by the sympathetic system and is the correct answer choice). The orgasm (emission and ejaculation) and resolution (constriction of erectile arteries) phases of the male sexual act are under sympathetic control ("Emission of sperm and semen through the urethra", "Ejaculation of sperm and semen" and "Resolution, or constriction of arteries in the erectile tissue" are under control of the sympathetic nervous system and can be eliminated).

In a frog embryo, which of the following cell groups gives rise to the muscles? Question 14 Answer Choices A. Ectoderm B. Endoderm C. Mesoderm D. Neural tube

C. In a frog embryo, the mesoderm cell group gives rise to the muscles. The mesoderm forms muscles, blood, bone, reproductive organs, and kidneys.

Which of the following is not derived from the inner cell mass of a blastocyst? Question 16 Answer Choices A. Embryo B. Amnion C. Trophoblast D. Allantois

C. The trophoblast is not derived from the inner cell mass of a blastocyst. A blastocyst consists of an outer cell mass and an inner cell mass. The outer cell mass, or trophoblast, develops first into the chorion and ultimately into the placenta. The inner cell mass develops into the embryo, amnion, yolk sac and allantois (leaving these as incorrect answer choices).

Bone tissue can be compact or spongy. Which of the following is found in spongy bone but NOT in compact bone? Question 21 Answer Choices A. Osteons B. Osteocytes C. Red bone marrow D. Blood vessels

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).

Skeletal muscle is attached to bone by: Question 17 Answer Choices 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).

How are peptidases activated in the duodenum? Question 32 Answer Choices 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.

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).

Human chorionic gonadotropin (hCG) is secreted from which structure to help maintain pregnancy? Question 18 Answer Choices A. Inner cell mass B. Morula C. Zygote D. Trophoblast

D. Human chorionic gonadotropin (hCG) is secreted from the trophoblast to help maintain pregnancy. Human chorionic gonadotropin (hCG) is secreted from the trophoblast (which ultimately becomes the placenta) during early development to keep the corpus luteum from degenerating. This keeps progesterone high in order to maintain the uterine lining. The inner cell mass ultimately becomes the embryo and does not secrete hCG, the zygote is the initial cell formed when the sperm and egg fuse, and the morula is a solid ball of cells formed after many cell divisions of the zygote, making each of these incorrect answer choices.

At which stage of development are the three germ layers (the ectoderm, the mesoderm, and the endoderm) first found? Question 13 Answer Choices A. Neurula B. Morula C. Blastula D. Gastrula

D. The three germ layers (the ectoderm, the mesoderm, and the endoderm) are first found at the gastrula stage of development. The three germ layers are first formed during gastrulation. The morula and the blastula occur prior to gastrulation (making them incorrect answer choices), and the neurula is derived from ectodermal cells formed during gastrulation (neurula is wrong and gastrula is correct).

During fertilization: Question 3 Answer Choices 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).

Osteoclasts are inhibited as part of bone remodeling by which hormone? Question 43 Answer Choices A. Calcitriol B. Parathyroid hormone C. Cortisol D. Calcitonin

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).

What best characterizes alveolar ducts, which follow the respiratory bronchioles? Question 27 Answer Choices 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.

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).

Which route describes how filtrate moves through the nephron? Question 23 Answer Choices 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

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).

All of the following are types of dense connective tissue EXCEPT: Question 37 Answer Choices A. adipose tissue. B. bones. C. ligaments. D. tendons.

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).

Which of the following statements about bile is/are true? Bile emulsifies lipids for easier digestion. The amphipathic nature of bile allows it to digest lipids. Bile is produced by the liver and gallbladder. Question 11 Answer Choices 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).

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? Question 29 Answer Choices A. Epidermis B. Dermis C. Hypodermis D. Subcutaneous tissue

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).

The luteal phase of menstruation is consistently 14 days in length, yet normal menstrual cycles can vary anywhere from 21 to 35 days. During which phase of the cycle does this variation occur? Question 7 Answer Choices A. Secretory phase B. Ovulatory phase C. Follicular phase D. Menstrual phase

C. The luteal phase of menstruation is consistently 14 days in length, yet normal menstrual cycles can vary anywhere from 21 to 35 days. This variation occurs during the follicular phase of the cycle. The phases of the ovary drive activity in the uterus during the menstrual cycle, so variability in the length of the cycle lies with the ovarian phases. The ovulatory phase really refers to the length of time during which the egg is viable; though this can vary from 24-48 hours, this is not enough to account for days' worth of differences in the length of menstrual cycles. However, the follicular phase can be variable enough to cause normal menstrual cycles to have a great deal of variation. The menstrual and secretory phases are uterine rather than ovarian and therefore would not cause this variation.

Which of the following statements about the blastula is true? Question 4 Answer Choices A. The inner cell mass develops into the embryo and the trophoblast develops into the placenta B. The estrogen and progesterone in birth control pills prevent pregnancy by preventing blastulation. C. The placenta forms from the trophoblast by the end of the first month of pregnancy. D. The entire blastula undergoes differentiation into the three primary germ layers during gastrulation.

A. In the blastula, the inner cell mass develops into the embryo and the trophoblast develops into the placenta. The blastula consists of an outer layer of cells called the trophoblast, a mostly-hollow core called the blastocoel, and an inner clump of cells called the inner cell mass. The blastula is the structure that implants in the wall of the uterus, with the inner cell mass developing into the embryo, and the trophoblast cells ultimately becoming the placenta. Full formation of the placenta takes approximately three months and is complete at the end of the first trimester. Only the inner cell mass undergoes differentiation into the primary germ layers, and the estrogen and progesterone in birth control pills prevent ovulation, not blastulation.

What are the end products of oogenesis if fertilization occurs? Question 3 Answer Choices A. One ovum, two polar bodies B. One secondary oocyte, one polar body C. One primary oocyte, two polar bodies D. Three polar bodies

A. One ovum, two polar bodies

Which of the following is derived from embryonic ectoderm? Question 15 Answer Choices A. Gonads B. Cerebellum C. Liver D. Muscle

B. The cerebellum is derived from embryonic ectoderm. The ectoderm forms the skin and the nervous system, including the brain.

Why are women who wish to breastfeed counseled against taking birth control pills that combine estrogen and progestins as the means to block ovulation? Question 6 Answer Choices A. High levels of estrogen and progesterone inhibit follicle stimulating hormone as well as ovulation. B. High levels of estrogen and progesterone inhibit prolactin as well as ovulation. C. High levels of estrogen and progesterone inhibit relaxin as well as ovulation. D. High levels of estrogen and progesterone inhibit oxytocin as well as ovulation.

B. Women who wish to breastfeed counseled against taking birth control pills that combine estrogen and progestins as the means to block ovulation because high levels of estrogen and progesterone inhibit prolactin, the hormone responsible for milk production at the mammary glands. This is beneficial during pregnancy when there may not be a baby to feed, but needs to not occur during times of active lactation. These hormones do not inhibit oxytocin and while they do inhibit follicle stimulating hormone, FSH is not involved in lactation. Similarly, relaxin, the hormone of pregnancy that loosens the joints, is not inhibited by these hormones.

Which of the following is a FALSE statement about the birthing process? Question 44 Answer Choices 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.

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).

Why are the human testes held outside of the body? Question 1 Answer Choices A. To accommodate the placement of erectile tissue B. Temperature regulation for proper spermatogenesis C. Temperature regulation for proper testosterone production D. To allow easy access to the vas deferns

B. Temperature regulation for proper spermatogenesis

What role does the macula densa (in the distal tubule) play in regulating blood pressure? Question 7 Answer Choices 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.

How do troponin and tropomyosin work to regulate skeletal muscle contraction? Question 33 Answer Choices 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.

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).

What type of stem cell specifically forms the cells of the body? Question 5 Answer Choices A. Totipotent B. Embryonic C. Somatic D. Pluripotent

D. Pluripotent

A mother just gave birth to a child and directly experienced the effects of oxytocin. What are the possible effects of oxytocin? I. A decrease in oxytocin causes labor to begin. II. Once labor begins, the posterior pituitary increases secretion of oxytocin which causes increased uterine contractions. III. Oxytocin facilitates milk let-down for breastfeeding. Question 2 Answer Choices A. II and III only B. I, II, and III C. III only D. I and II only

A. A mother just gave birth to a child and directly experienced the effects of oxytocin. The possible effects of oxytocin are II and III only. I. A decrease in oxytocin causes labor to begin. II. Once labor begins, the posterior pituitary increases secretion of oxytocin which causes increased uterine contractions. III. Oxytocin facilitates milk let-down for breastfeeding. Item I is false: It is a drop in progesterone, not oxytocin, that causes labor to begin (choices with Item I can be eliminated). Since both remaining answer choices include Item III, Item III must be true and you can focus on Item II. Item II is true: Once labor begins, the secretion of oxytocin by the posterior pituitary is increased via a positive feedback mechanism, and this functions to increase the intensity of uterine contractions (choice "III only" can be eliminated). Note that Item III is in fact true: After parturition, oxytocin release (stimulated by suckling) facilitates milk let-down.

A researcher uses a radioactive label to trace the development of the GI glands in chicken embryos. From what primary germ layer do they come? Question 3 Answer Choices A. Endoderm B. Ectoderm C. Blastopore D. Mesoderm

A. A researcher uses a radioactive label to trace the development of the GI glands in chicken embryos. They come from the endoderm. The endoderm gives rise to the epithelial lining of the GI tract (except for the nasal, oral, and anal epithelium), the respiratory tract, and the urogenital organs and ducts. It also gives rise to the GI glands and the urinary bladder. The ectoderm gives rise to the nervous system, the cornea and lens, the pituitary gland, the adrenal medulla, the epidermis, and the nasal, oral, and anal epithelium. The mesoderm gives rise to all muscle, bone, connective tissue, cardiovascular system, lymphatic system, urogenital organs, and the dermis. The blastopore is not a primary germ layer and will eventually give rise to the anus.

A woman with type B- blood type experiences a miscarriage during the 10th week of her first pregnancy. The blood type of the father is unknown at the time. Should fetal hemolytic disease be of sufficient concern to administer Rhogam (anti-Rh antibodies)? Question 5 Answer Choices A. Yes; without knowing the blood type of the father, the fetus may have been Rh+ which could impact future pregnancies B. Yes; Rhogam should always be administered after a miscarriage, no matter what the mother's blood type. C. No; the risks of administering Rhogam are typically outweighed by the benefits to the mother. D. No; Rhogam should be given to women with Rh+ positive blood types to prevent hemolysis in Rh- fetuses.

A. A woman with type B- blood type experiences a miscarriage during the 10th week of her first pregnancy. Yes, fetal hemolytic disease be of sufficient concern to administer Rhogam (anti-Rh antibodies); without knowing the blood type of the father, the fetus may have been Rh+ which could impact future pregnancies. Rhogam counteracts antibodies that the body of a mother with Rh- blood may form when she is exposed to Rh+ blood from a baby during delivery or during the removal of the products of conception at the time of a miscarriage. Hemolysis during the current pregnancy is less of a concern; rather the drug is given to prevent hemolysis in future pregnancies when the antibodies would already be well established. The reasons to administer the drug are not related to how the pregnancy ended and are related to the fetus or baby rather than the mother.

Why is light-headedness and occasional dizziness a common symptom for women in their second trimester of pregnancy? Question 4 Answer Choices A. While the maternal circulatory system has expanded to accommodate the needs of the growing fetus, the production of blood itself needs to fill in the new capacity. B. Maternal myoglobin production has increased and stores more oxygen in the mother's muscles to prepare for labor. C. The increased affinity for oxygen demonstrated by fetal hemoglobin removes too much oxygen from the maternal blood supply. D. Pressure from the expanding uterus makes breathing difficult, thus limiting the amount of oxygen exchange with the blood supply.

A. Light-headedness and occasional dizziness is a common symptom for women in their second trimester of pregnancy because while the maternal circulatory system has expanded to accommodate the needs of the growing fetus, the production of blood itself needs to fill in the new capacity. During the second trimester, the capacity to supply blood to the fetus is expanding, but the maternal hematopoietic tissues take longer to produce enough blood to fill what the new vasculature can hold. This can lead to dizziness until that gap in capacity closes. Obstruction of breathing by the uterus typically does not take place until the third trimester and though it can impinge on lung capacity, it does not interfere with circulatory exchange. Though fetal hemoglobin has a higher affinity for oxygen than the maternal hemoglobin, this is not so extensive as to actively deprive the mother of oxygen. By that same token, the muscles are not storing so much oxygen as to deprive standard circulation.

Which of the following is the correct order of events in fertilization? Question 11 Answer Choices A. Sperm penetrates oocyte --> Second polar body is released --> Syngamy (fusion of nuclei) --> Cleavage B. First polar body is released --> Ovulation --> Second polar body is released --> Sperm penetrates oocyte --> Cleavage C. First polar body is released --> Ovulation --> Sperm penetrates oocyte Syngamy (fusion of nuclei) --> Second polar body is released --> Cleavage D. Sperm penetrates oocyte --> First polar body is released -->Syngamy (fusion of nuclei) --> Second polar body is released --> Cleavage

A. The correct order of events in fertilization is Sperm penetrates oocyte --> Second polar body is released --> Syngamy (fusion of nuclei) --> Cleavage. The first polar body is released prior to ovulation. After the sperm penetrates the oocyte, the sperm and oocyte nuclei remain separate until the oocyte completes meiosis II and releases the second polar body. Until this time the fertilized oocyte is a dikaryon (one cell, two nuclei). After the second polar body is released, the two nuclei fuse, and the cell is known as a zygote; the zygote then begins a period of rapid cell division known as cleavage.

A block in prophase II of spermatogenesis would result in: Question 14 Answer Choices 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).

At what stage of the sliding filament cycle is ATP hydrolyzed? Question 28 Answer Choices A. Resetting the myosin head to bind actin again Correct Answer (Blank) B. Release of actin C. Binding of the myosin head to actin D. During the power stroke

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).

All of the following are true statements EXCEPT: Question 13 Answer Choices 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).

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? Question 6 Answer Choices 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).

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? Question 22 Answer Choices 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.

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).

Oogenesis is different from spermatogenesis in that: Question 1 Answer Choices 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).

The primary function of fructose and buffers in semen is to help spermatozoa survive the path from the: Question 45 Answer Choices 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.

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).

Which of the following is an incorrect matching of developmental phase and characteristics? Question 8 Answer Choices 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).

The function of the loop of Henle is to: Question 42 Answer Choices 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.

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).

Which of the following does NOT describe the esophagus? Question 16 Answer Choices 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).

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

Anaphase I of meiosis occurs in which of the phases of oocyte development shown above? Question 13 Answer Choices A. 1 B. 2 C. 3 D. 4

Anaphase I of meiosis occurs in phase 2 of oocyte development shown above. During meiosis, there are two rounds of cell division: meiosis I and meiosis II. During embryonic development of females, oogenesis proceeds up to the formation of primary oocytes, which are arrested in meiotic prophase I. They will remain arrested at this stage up until the time that they prepare for ovulation and complete meiosis I, including going through anaphase I, to form secondary oocytes which are ovulated. Stage 2, the progression from primary to secondary oocytes, includes anaphase I.

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? Question 30 Answer Choices A. Water, ions, urea, glucose B. Water, ions, urea C. Water, proteins, ions, urea D. Water, urea, proteins, glucose

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).

What allows for a similarity in how cardiac muscle and smooth muscle transmit action potentials from cell to cell? Question 35 Answer Choices A. Presence of tight junctions B. Presence of gap junctions C. Presence of voltage-gated sodium channels D. Presence of desmosomes

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).

Which of the following types of renal vasculature are NOT responsible for returning components to the circulatory system as part of filtrate adjustment? Question 9 Answer Choices A. Efferent arterioles B. Afferent arteriole 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).

All of the following are true of the bacteria living in the large intestine EXCEPT: Question 19 Answer Choices 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.

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).

Where would somatic stem cells be found in an adult human? Question 8 Answer Choices A. Gonads B. Brain C. Bone marrow D. Epidermis

C. Somatic stem cells would be found in the bone marrow of an adult human. Somatic stem cells are multipotent so they can become several different (but not all) types of cells. They are found in the hematopoietic tissue of the bone marrow. The gonads produce gametes, the neurons of the brain are fully differentiated and so is the epidermis (the top most layer of skin).

A physician is treating four different women, each of whom is taking oral birth control pills (BCP). BCPs generally function to inhibit gonadotropin release and therefore inhibit ovulation. Which one of the following patients should be LEAST worried that the BCP will be ineffective? Question 17 Answer Choices A. A patient taking an anti-depressant drug, which early studies have shown might alter hormone levels B. A patient who is taking a weight-loss prescription, which elevates her liver metabolism levels significantly C. A patient who is taking a GnRH antagonist, which competes with GnRH for the GnRH receptor D. A patient with irritable bowel syndrome, who has been suffering from severe diarrhea frequently in the last month

C. A physician is treating four different women, each of whom is taking oral birth control pills (BCP). BCPs generally function to inhibit gonadotropin release and therefore inhibit ovulation. A patient who is taking a GnRH antagonist, which competes with GnRH for the GnRH receptor should be LEAST worried that the BCP will be ineffective. It is possible that a patient with elevated liver metabolism would degrade the hormones in the BCP faster than usual, and hormone levels could be lower than they should be (this patient should be worried and "A patient who is taking a weight-loss prescription, which elevates her liver metabolism levels significantly" can be eliminated). It is possible that a patient with severe diarrhea, because of increased motility in the GI tract, is not absorbing the hormones in the pill properly (this patient should also be worried and "A patient with irritable bowel syndrome, who has been suffering from severe diarrhea frequently in the last month" can be eliminated). If a certain anti-depressant drug changes hormone levels in the body, it is possible that it might interact with or affect the hormones in the BCP (this patient should be worried and "A patient taking an anti-depressant drug, which early studies have shown might alter hormone levels" can be eliminated). However, if a GnRH antagonist competes for the GnRH receptors, this would reduce the effects of GnRH, leading to a decrease in the release of the gonadotropins, which mimics the effect of the BCP. This patient has little to worry about ("A patient who is taking a GnRH antagonist, which competes with GnRH for the GnRH receptor" is correct). In fact, in certain cases, GnRH antagonists can be used to inhibit ovulation.

When does a secondary oocyte become an ootid? Question 1 Answer Choices A. During the luteal phase of the menstrual cycle, after ovulation but before fertilization. B. In utero, where the secondary oocyte will remain frozen in metaphase II until puberty. C. After fertilization, but before the egg and sperm nuclear membranes fuse. D. During the follicular phase of the menstrual cycle, just prior to ovulation.

C. A secondary oocyte become an ootid after fertilization, but before the egg and sperm nuclear membranes fuse. Each month during a woman's reproductive years, a few primary oocytes complete meiosis I to become secondary oocytes. These secondary oocytes never progress beyond metaphase II unless they are fertilized, at which time they complete meiosis II to become ootids, then develop into mature ova in a matter of minutes.

During the menstrual cycle, the corpus luteum degrades, but if a fertilized ovum implants in the uterus, the corpus luteum persists. Which of the following hormones supports the corpus luteum during pregnancy? Question 3 Answer Choices A. Progesterone B. Lutenizing hormone C. Human chorionic gonadotropin D. Estrogen

C. During the menstrual cycle, the corpus luteum degrades, but if a fertilized ovum implants in the uterus, the corpus luteum persists. Human chorionic gonadotropin supports the corpus luteum during pregnancy. Human chorionic gonadotropin (hCG) is secreted by the trophoblast, beginning at implantation. hCG plays a role similar to that of lutenizing hormone (LH) in maintaining the corpus luteum. In the presence of hCG, the corpus luteum continues to secrete estrogen and progesterone to maintain the uterine lining so that the pregnancy is not lost. The trophoblast ultimately develops into the placenta (by about the 3rd month of gestation), which takes over the endocrine role of the corpus luteum.

Early in gestation, the human embryo is without gender. As development progresses, female sex may result from: I. absence of genetically encoded hormonal influences. II. lack of inhibition of default pathways. III. absence of genetically encoded inhibitory hormones. Question 5 Answer Choices A. I only B. I and II only C. I, II, and III D. II and III only

C. Early in gestation, the human embryo is without gender. As development progresses, female sex may result from I, II, and III. I. absence of genetically encoded hormonal influences. II. lack of inhibition of default pathways. III. absence of genetically encoded inhibitory hormones. Item I is true: testosterone is genetically encoded and required to form the male system; in its absence the female system develops. Item II is true: the female system is considered to be the "default" system, since no specific trigger is required to initiate its development, only the absence of the triggers for the male system. If the "default" pathway is not inhibited, it will develop. Item III is true: one of the hormones produced during male development is Müllerian Inhibiting Factor (MIF) which acts to suppress female development. In its absence, the female system develops.

Which of these processes happens last in embryogenesis? Question 2 Answer Choices A. Gastrulation B. Blastulation C. Neurulation D. Fertilization

C. Neurulation happens last in embryogenesis. Neurulation begins with the formation of the neural tube from embryonic ectoderm and follows gastrulation. Both fertilization and blastulation occur prior to gastrulation (and neurulation).

Which of the following structures are derivatives of the ectoderm? I. Epidermis of the skin II. Dermis of the skin III. Sweat glands Question 12 Answer Choices A. I and II only B. I, II, and III C. I and III only D. II and III only

C. Structures I and III only are derivatives of the ectoderm. I. Epidermis of the skin II. Dermis of the skin III. Sweat glands The skin's epidermis and its derivatives (which include hair, nails, and sweat glands) are derived from the ectoderm (Items I and III are true). The dermis of the skin is derived from the mesoderm (Item II is false).

Which of the following is a true statement? Question 11 Answer Choices A. Inhibin, released by interstitial cells, inhibits FSH release. B. The posterior pituitary secretes LH, which acts on interstitial cells. C. Interstitial cells secrete testosterone, which inhibits release of LH and FSH D. The anterior pituitary secretes FSH, which acts on interstitial cells.

C. The following is a true statement: Interstitial cells secrete testosterone, which inhibits release of LH and FSH. Leydig cells secrete testosterone, which causes development of male secondary sexual characteristics in males. Testosterone feeds back to the anterior pituitary (and the hypothalamus) to inhibit release of FSH and LH. The anterior pituitary does secrete FSH, however it stimulates Sertoli cells (also known as sustentacular cells), not Leydig cells ("The anterior pituitary secretes FSH, which acts on interstitial cells" is wrong). LH is also secreted by the anterior pituitary (not the posterior, "The posterior pituitary secretes LH, which acts on interstitial cells" is wrong) and stimulates Leydig cells (also known as interstitial cells) to secrete testosterone ("The posterior pituitary secretes LH, which acts on interstitial cells" is wrong). Sertoli cells (not Leydig cells) secrete inhibin, which decreases FSH secretion from the anterior pituitary ("Inhibin, released by interstitial cells, inhibits FSH release" is wrong).

The structure which secretes progesterone during the luteal phase of the ovarian cycle is called the: Question 16 Answer Choices A. ovarian medulla. B. follicle. C. corpus luteum D. corona radiata.

C. The structure which secretes progesterone during the luteal phase of the ovarian cycle is called the corpus luteum. Follicle is incorrect since the follicle is present during the follicular phase, not the luteal phase. The corona radiata is the group of cells surrounding the oocyte after ovulation, and the ovarian medulla is mostly connective tissue and blood vessels and does not secrete anything, so both of these may be eliminated. The corpus luteum is the remnant of the follicle after ovulation has occurred. It is an endocrine structure that secretes progesterone (and which the luteal phase is named for).

One of the first hormones produced by a developing embryo is hCG, human chorionic gonadotropin. The function of hCG is to prolong the life of the corpus luteum, ensuring that the endometrium is maintained until full development of the placenta by 3 months of gestation. hCG is most like which of the following hormones? Question 9 Answer Choices A. Estrogen B. Progesterone C. LH D. FSH

C. hCG is most like LH. The LH (luteinizing hormone) surge in the middle of the menstrual cycle triggers both ovulation and the conversion of the follicular remnants into the corpus luteum, which then secretes progesterone and estrogen. However, levels of LH rapidly fall, and in the absence of LH the corpus luteum only survives for about two weeks. At the end of that time period, the corpus luteum degenerates, the levels of progesterone and estrogen fall, and menstruation occurs. In order to maintain the endometrium in the case of pregnancy, levels of progesterone and estrogen must remain elevated, and in order keep the levels elevated, the corpus luteum must be maintained. hCG takes on the role of LH in this regard. FSH does not affect formation or maintenance of the corpus luteum. Further it does not make logical sense for hCG to be like progesterone or estrogen; if this was the case, there would be no need to maintain the corpus luteum to secrete those hormones.

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? Question 36 Answer Choices A. Increased O2, increased CO2 B. Increased O2, decreased CO2 C. Decreased O2, increased CO2 D. Decreased O2, decreased CO2

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).

The male reproductive system includes accessory glands, gonads and other genital structures (both internal and external). Which of the following is true? Question 26 Answer Choices 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.

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).

The Mullerian ducts in females: Question 25 Answer Choices 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.

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).

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)? Question 39 Answer Choices 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

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.

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? Question 24 Answer Choices A. Chest wall elasticity B. Diaphragm function C. Inspiration D. Passive expiration

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).

In premature deliveries before 30 weeks gestation, pulmonary surfactant has not yet been produced. What difficulties would be expected in these infants? Question 31 Answer Choices 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

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).

A mesodermal cell originally destined to become a heart cell gets transplanted to another location where cells become bone cells. The mesodermal cell now develops into a bone cell instead of a heart cell. The process that occurred is: Question 17 Answer Choices A. imprinting. B. differentiation. C. determination. D. induction.

D. A mesodermal cell originally destined to become a heart cell gets transplanted to another location where cells become bone cells. The mesodermal cell now develops into a bone cell instead of a heart cell. The process that occurred is induction. When one type of cell is transplanted and then becomes more like its surrounding cells, that process is called induction. This typically must happen early enough in development so that specific genes are not yet turned on. Once the genetic program in a cell has been invoked, that cell's fate has been determined and the cell can no longer be induced to become a different cell (determination is wrong). Differentiation is the actual act of transforming into a more mature cell type (differentiation is wrong), and imprinting occurs when a newborn animal sees its mother for the first time and has nothing to do with cellular development (imprinting is wrong).

Which of the following cells is NOT haploid? Question 10 Answer Choices A. Secondary spermatocyte B. Spermatozoon C. Spermatid D. Primary spermatocyte

D. A primary spermatocyte is NOT haploid. The spermatozoon, spermatid, and the secondary spermatocyte all occur in spermatogenesis after the first meiotic division; thus they have all had their chromosome numbers reduced and are haploid (since they are haploid, they can be eliminated as answer choices). The primary spermatocyte gets activated from the spermatogonium and is ready to enter meiosis I, thus it has not undergone any divisions in meiosis and is still diploid (primary spermatocyte is not haploid and the correct answer choice).

Which of the following is from mesoderm? Question 6 Answer Choices A. Epithelial cells of the intestine B. Epidermis C. Neurons D. Cardiac muscle

D. Cardiac muscle is from mesoderm. Mesoderm is the "middle" layer of the three primary germ layers, and as such forms "middle level" structures in the body, such as bones, muscles, blood vessels, the heart, the lungs, non-glandular organs in general. The epithelial cells of the intestine come from endoderm ("inner level"), and the epidermis and neurons come from ectoderm ("outer level"). Note that the neurons are not on the outer edge of the body, but early in development the ectoderm folds inward to form the nervous system.

Follicular development is stimulated by a rise in FSH and normally leads to a subsequent rise in estrogen. The failure of a developing follicle to produce estrogen would cause which of the following events? I. Lack of endometrial development II. Failure to ovulate III. Premature menstruation Question 8 Answer Choices A. II and III B. I only C. I, II, and III D. I and II

D. I. Lack of endometrial development II. Failure to ovulate III. Premature menstruation The failure of a developing follicle to produce estrogen would cause a lack of endometrial development and failure to ovulate. Rising estrogen levels during the follicular phase of the menstrual cycle cause the endometrial lining of the uterus to thicken; a lack of estrogen would prevent the development of the endometrium (Item I is true). Also, the rising levels of estrogen have a positive feedback effect on LH, causing the LH surge that triggers ovulation. Without estrogen there would be no surge and no ovulation (Item II is true). However, menstruation would most likely be delayed; it is the sudden drop in estrogen and progesterone at the end of the cycle that lead to endometrial degradation and menstruation. If estrogen isn't present and the endometrium fails to develop, there would likely be a complete cessation of menstruation (amenorrhea; Item III is false).

If a baby is born with both male and female genitalia, which of the following is a possible explanation? Question 18 Answer Choices A. The baby is genetically female and there was a mutation in the gene for Wolffian inhibiting factor. B. The baby is genetically male and there was a mutation in the gene for Wolffian inhibiting factor. C. The baby is genetically XXY and the extra X chromosome caused a surge in estrogen leading to development of both genitalia. D. The baby is genetically male and there was a mutation in the gene for Mullerian inhibiting factor.

D. If a baby is born with both male and female genitalia, a possible explanation for this is that the baby is genetically male and there was a mutation in the gene for Mullerian inhibiting factor. The Y chromosome must be present for male genitalia to develop, and Mullerian inhibiting factor (MIF) must be present to prevent female genitalia from developing. If the Y chromosome is present, and MIF is absent or mutant (non-functional), then both sets of genitalia will develop. There is no such thing as Wolffian inhibiting factor ("The baby is genetically female and there was a mutation in the gene for Wolffian inhibiting factor" and "The baby is genetically male and there was a mutation in the gene for Wolffian inhibiting factor" are wrong). An extra X chromosome would not lead to increased estrogen, and even if it did, as long as MIF was present, no female genitalia would develop ("The baby is genetically XXY and the extra X chromosome caused a surge in estrogen leading to development of both genitalia" is wrong).

How are multipotent stem cells different in their capabilities than pluripotent stem cells? Question 7 Answer Choices A. Multipotent stem cells form all the extraembryonic membranes while pluripotent stem cells form the embryo. B. Multipotent stem cells can become any of the three primary germ layers, while pluripotent stem cells can become several different types of cells from a single primary germ layer. C. Multipotent stem cells form all the cells of the body while pluripotent stem cells can also form the cells of the placenta. D. Multipotent stem cells can become several different types of cells from a single primary germ layer, while pluripotent stem cells can become any of the three primary germ layers.

D. Multipotent stem cells can become several different types of cells from a single primary germ layer, while pluripotent stem cells can become any of the three primary germ layers. Pluripotent stem cells are the embryonic stem cells that form the embryo itself (the three primary germ layers). Totipotent stem cells precede this and form both the embryo and the placenta.

The epidermis of the skin is embryologically derived from the same germ layer that gives rise to which of the following? Question 1 Answer Choices A. Skeletal muscle B. Liver C. Stomach D. Spinal cord

D. The epidermis of the skin is embryologically derived from the same germ layer that gives rise to the spinal cord. You must memorize which adult tissues are derived from each of the three primary germ layers. The endoderm give rise to the stomach, the colon, the liver, the pancreas, the urinary bladder, the lining of the urethra, and the epithelial parts of the trachea, lungs, pharynx, thyroid, parathyroid, and intestines. The mesoderm gives rise to skeletal muscle, the skeleton, the dermis of the skin, connective tissue, the urogenital system, all parts of the cardiovascular system, the blood, and the spleen. The ectoderm gives rise to the central nervous system (brain and spinal cord), the lens of the eye, ganglia and nerves, head connective tissue (pharyngeal cartilages, hyoid bone, auditory ossicles, etc.), the epidermis, hair, sweat glands, and mammary glands. This content is important to know for the MCAT.

Low blood pressure and low blood volume trigger which of the following? Question 5 Answer Choices 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.

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? Question 18 Answer Choices 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).

Which of the following describes the path of travel for sperm in the female reproductive tract? Question 34 Answer Choices 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

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.

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? Question 40 Answer Choices 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

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).

The renal medulla is made up primarily of: Question 15 Answer Choices 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).

What two components are unique to the regulation of smooth muscle? Question 20 Answer Choices A. Myosin light chain kinase and troponin B. Troponin and tropomyosin C. Tropomyosin and calmodulin D. Calmodulin and myosin light chain kinase

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).

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? Question 38 Answer Choices A. Metabolic acidosis B. Overhydration due to inability to sweat C. Hypothermia due to inability to sweat D. Infection

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).