Term
| What are the macroscopic parts of the testes? Describe them. |
|
Definition
1. seminiferous tubules - the organs inside the testes; they are coiled tubules that connect to the external epididymis via the rete testis
2. rete testis - the simply straight tubules that connect the seminiferous tubules to the epididymis
3. epididymis - a coiled tube outside the testis that connects to the vas deferens via the rete testis
4. vas deferens - a straight tubule that widens into the ampulla, the feeds into the ejaculatory duct of the prostate gland |
|
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Term
| What is the neural pathway that the signals for sexual sensation from the penis travel to the brain? |
|
Definition
| sensory fibers in the distal end of the penis (the glans penis) send signals through the pudendal nerve, through the sacral plexus, up the spinal cord, and to undefined areas of the brain |
|
|
Term
| What is erectile dysfuncton? What causes it? How can it be treated? |
|
Definition
1. erectile dysfunction is a decreased ability or inability to get an erection
2. some drugs, neurological problems, and low testosterone levels can all cause ED; diabetes, atherosclerosis, and hypertension can also cause vascular problems, resulting in reduced NO release and impaired vasodilation, causing ED
3. ED caused by vascular problems can be treated with PDE-5 (phosphodiesterase-5) inhibitors such as cialis, levitra, and viagra |
|
|
Term
|
Definition
| they degrade c-GMP, a second messenger system involved in NO activity |
|
|
Term
| What is the function of the prostate gland? |
|
Definition
| it secretes calcium, citrate, clotting enzyme, profibrinolysin, and alkaline fluid during emission to contribute those ingredients to the semen |
|
|
Term
What is the function of each ingredient of the following ingredients of semen:
calcium, citrate, clotting enzyme, profibrinolysin, and alkaline fluid? |
|
Definition
1. increases the functionality of the tails of sperm
2. can be used by the sperm as an energy source
3. assists in forming a semen clot
4. assists in breaking up the semen clot
5. neutralizes the acidic environment of the vagina |
|
|
Term
| How does prostate size change with age? |
|
Definition
| is begins fairly small, but it grows at puberty in response to testosterone; at about 20 it reaches almost stationary size until about 50, when it may become enlarged for various reasons |
|
|
Term
| What problems can prostate cancer cause? How is it treated? |
|
Definition
1. cancerous cells often grow in response to testosterone, even are it metastasizes; prostate cancer is responsible for 2-3% of the deaths in men
2. treatments include the removal of the testes or treatment with estrogens |
|
|
Term
| What problems can benign prostatic fibroadenomas cause? |
|
Definition
| abnormal non-testosterone-related growth of the gland; they can also inhibit urinary function |
|
|
Term
| Describe the physical structure of the seminal vesicles. What is their function? |
|
Definition
1. They are tubes lined with secretory epithelium located on either side of the prostate gland
2. The epithelium ejects seminal fluid including mucus, citrate, fructose, prostaglandins, and fibrinogin into the ejaculatory duct inside the prostate gland, adding the bulk of the semen |
|
|
Term
| What is believed to be the function of the prostaglandins in the semen? |
|
Definition
| they are believed to make the servical mucus more receptive to sperm movement and possibly cause backward, reverse-peristalic contractions of the uterus to move sperm closer to the ovaries |
|
|
Term
| What is the function of the bulbourethral gland? |
|
Definition
| it supplies the urethra with additional mucus for the semen |
|
|
Term
| What are spermatogonia? What is their function in the reproductive system? |
|
Definition
1. they are immature germ cells originally formed from primordial germ cells
2. they undergo and continue to undergo mitosis and some eventually develop into primary spermatocytes, which can undergo meiosis I to produce secondary spermatocytes, which can undergo meiosis II to produce spermatids, which become sperm |
|
|
Term
| What are Sertoli cells? What is their function in the reproductive system? |
|
Definition
1. large cells with overflowing cytoplasm that envelop spermatogonia
2. they release spermatogenic substances which encourage spermagonia to develop into primary spermatocytes; they also allow a place for testosterone and DHT to access the spermagonia |
|
|
Term
| What cause Sertoli cells to release spermatogenic substances? What is the feedback loop for this? What is the mechanism for this feedback control? |
|
Definition
1. FSH
2. If the seminiferous tubules fail to produce sperm, FSH increase; when spermatogenesis proceeds too quickly, FSH decreases
3. the feedback is thought to be due to inhibin, which decreases FSH secretion and may decrease GnRH secretion form the hypothalamus |
|
|
Term
| What is a spermatid? A spermazoon? How long does it take to produce sperm from spermagonia? |
|
Definition
1. the initial result of meiosis II in the seminiferous tubules; these cells are spherical
2. the result of spermatid development; spermazoa have a head and tail and are also called sperm
3. 74 days |
|
|
Term
| Describe the head of the sperm. Describe the tail. |
|
Definition
1. It contains the nucleus and a thin membrane around the surface with a thick cap on the tip called an acrosome; the acrosome is made mostly out of golgi apparatus, containing proteolytic enzymes such as hyaluronidase to help the sperm get to the egg
2. the tail is a flagellum with a central skeleton of 9 + 2 configuration called an axoneme, a thin membrane covering the tail, and a collection of mitochondria surrounding the axoneme |
|
|
Term
| How quickly can sperm travel? |
|
Definition
|
|
Term
| What hormones directly affect spermatogenesis? |
|
Definition
| testosterone, LH, FSH, estrogens, and hGH |
|
|
Term
| Where is testosterone made and secreted in the male reproductive system? What is the function of testosterone in spermatogenesis? |
|
Definition
1. in the Leydig cells in the interstitium of the testis
2. it is essential for growth and division of the testicular germinal cells |
|
|
Term
| Where is FSH secreted? What is its function in the male reproductive system? |
|
Definition
1. the anterior pituitary
2. stimulates the Sertoli cells to initiate spermatogenesis and spermiogenesis |
|
|
Term
| Where is LH secreted? What is its function in the male reproductive system? |
|
Definition
1. secreted by the anterior pituitary gland
2. stimulates Leydig cells to produce testosterone |
|
|
Term
|
Definition
| The conversion of stermatids into sperm |
|
|
Term
| Where are estrogens formed and secreted in the male reproductive system? What are their function in that system? |
|
Definition
1. they are formed from testosterone by Sertoli cells when stimulated by FSH
2. they are probably essential for spermiogenesis |
|
|
Term
| Where is hGH secreted from? What is its function in the male reproductive system? |
|
Definition
1. the anterior pituitary
2. it controls the background metabolic functions of the testes and promotes early division of the spermatogonia themselves |
|
|
Term
| Where do sperm travel after formation? Why does it take them so long to move through the male reproductive system? |
|
Definition
1. They travel through the epididymis over the course of a few days
2. Initially sperm are incapable for moving on their own and even after 18-24 hours, when they are capable of movement, they still have inhibitory proteins that reduce their movement |
|
|
Term
| How many sperm are formed every day? Where are the stored? How long can they be stored? |
|
Definition
1. 120M
2. in the vas deferens
3. about a month |
|
|
Term
| How do sperm react to the increased temperature of the vagina compared to the testes and vas deferens? |
|
Definition
| the sperm have increased mobility in high temperatures, so they will travel faster in the vagina |
|
|
Term
| About what percentage of the fluid in the semen is contributed by the vas deferens? The seminal vesicles? The prostate gland? The bulbourethral glands? |
|
Definition
1. about 10%
2. about 60%
3. about 30%
4. a small amount |
|
|
Term
| What is the average pH of semen? What happens shortly after semen is ejaculated? |
|
Definition
1. about 7.5
2. the sperm are initially immobile, being held together by the mucus; the alkaline fluid of the semen somewhat neutralizes the acidic environment of the vagina; the semen forms a weak clot due to fibrinogen; the clot is thought to help it travel up toward the cervix while the prostaglandins stimulate reverse peristalsis movement; the clot and mucus are broken up in 15-30 minutes by fibrinolysis and the sperm become more mobile and begin moving toward the cervix and the ovaries |
|
|
Term
| How long will sperm survive in the vagina without fertilization? Why don't sperm die faster in the male reproductive system? |
|
Definition
1. 24-48 hours
2. besides being nourished in the male reproductive system, sperm are made and stored below body temperature (the testes and vas deferens remain a few degrees lower than body temperature because they are away from the body core) |
|
|
Term
| What is capacitation of the sperm? |
|
Definition
| the mobility of the sperm is reduced by inhibitory factors within the semen |
|
|
Term
| What secretes the inhibitory factors of the semen? How are the inhibitory factors removed? |
|
Definition
1. genital duct epithelia
2. the uterine and fallopian tube fluids wash away inhibitory factors that suppress sperm activity |
|
|
Term
| What is the function of cholesterol in the semen? |
|
Definition
| 1. as sperm pass cholesterol vesicles in the semen, they uptake cholesterol and toughen up their acrosomes with it |
|
|
Term
| What are the functions of the acrosomes in the vaginal tract? |
|
Definition
| the acrosome protects the sperm during its forward motion; the acrosome will become weaker as it travels through the vaginal tract; as it becomes weaker, the acrosome uptakes calcium, which increases the force of flagellum movement and promotes the release of proteolytic enzymes to help penetrate the granulosa cell mass surrounding the ovum and later the zona pellucid of the ovum itself |
|
|
Term
| What is the zona pellucida? What is its significance in fertilization? |
|
Definition
1. a thick covering around the ovum itself that protects it and keeps other things out
2. Since it keeps things out, the sperm is unable to fertilize the egg; the sperm will release proteolytic enzymes that digest a path through the zona pellucida so the sperm can fertilize the egg |
|
|
Term
| How does the sperm get through the layer of granulosa cells surrounding the ovum? |
|
Definition
| it attaches to a receptor in the layer, which causes the release of proteolytic enzymes such as hyalyronidase, which digest the hyaluronic acid polymers that hold the layer together so the sperm can get through |
|
|
Term
| What happens to the sperm during fertilization? |
|
Definition
| the sperm's genome and the oocyte genome fuse and the oocyte digests the rest of the sperm's cellular components |
|
|
Term
| What happens after fertilization? |
|
Definition
| calcium ions diffuse inward through inward through the oocyte membrane and cause multiple cortical granules to be released into the perivitelline space (around the oocyte); these granules have substances that permeate the whole zona pellucida and prevent further binding of sperm to the receptors and cause bound sperm to unbind |
|
|
Term
| What is orchitis? What is its consequences to the male reproductive system? |
|
Definition
1. inflammation of the testes resulting from mumps
2. can cause sterlity |
|
|
Term
| What temperature do the testes need to be to be functional? What happens in cold weather? What happens in excessive temperatures? |
|
Definition
1. about 2 degrees below body temperature (about 33 degrees Celsius)
2. scrotal reflexes cause the scrotal musculature to contract, pulling the testes close to the body to maintain a fairly constant temperature
3. many cells, including the sperm, degenerate in high temperatures |
|
|
Term
| What is cryptorchidism? How is this treated? What is the usual cause of cryptorchidism? |
|
Definition
1. failure of the testes to descend from the abdomen into the scrotum at or near the time of birth
2. an operation is usually performed to cause the descent of the testes before adult sexual life begins
3. an abnormality in the testes to form testosterone; if this is the cause, manual descent of the testes will not allow fertility |
|
|
Term
| When do testes normally descend? What is the normal trigger for the descent of the testes? What happens if the testes don't descend? |
|
Definition
1. 3 weeks to 1 month before birth
2. testosterone
3. they will be unable to form sperm and the tubular epithelium will degenerate |
|
|
Term
| What is the approximate normal volume of ejaculated fluid? What is the normal sperm concentration? Below what level are males usually considered infertile? |
|
Definition
1. 3.5 mL
2. about 120M/mL
3. about 20M |
|
|
Term
| What are the causes for infertility in males? |
|
Definition
| destruction, damage, or removal of a part of the reproductive system; narrowing of the genital ducts or other abnormalities; orchitis; cryptorchidism; excessive temperatures (only present sperm are rendered inviable); lack of testosterone production; low sperm count; a significant number of sperm with abnormal sperm morphologies (such as two heads, two tails, problems with mobility, abnormally shaped heads or tails, etc) |
|
|
Term
| Besides the glans penis, what other areas can transmit signals of sexual stimulation? |
|
Definition
| anal epithelium, scrotum, perineal structures, and stimulation from the feeling of filling internal sexual structures or irritation of the structures (as with aphrodisiacs) |
|
|
Term
| What is cantharidin? What does it do? |
|
Definition
1. an aphrodisiac
2. it causes irritation to the internal organs, causing increased sexual stimulation |
|
|
Term
| What are nocturnal emissions? |
|
Definition
| 1. ejaculation due to psychic stimuli, such as a dream |
|
|
Term
| What is the first (physical) response to sexual stimulation in males? What is the mechanism? |
|
Definition
1. erection
2. parasympathetic impulses through the pelvis nerves from the sacral portion of the spinal cord release NO and vasoactive intestinal peptide in addition to ACh; NO activates guanylyl cyclase which produces cGMP, which causes the vasodilation of arteries in the penis and smooth muscle in the erectile tissue of corpora cavernosa and corpus spongiosum; vasodilation increases blood flow to the sinuses, causing increased NO release, feeding a positive feedback loop; the veins become pinched, resulting in an engorgement of the penis with blood, aka erection |
|
|
Term
| What organs in the male reproductive system contributes to erection? |
|
Definition
| urethral and bulbourethral glands release mucus during intercourse that aid in lubrication, but most lubrication comes from the female |
|
|
Term
| What is emission? What is the cause of emission in males? What is the mechanism? |
|
Definition
1. the release of fluid and sperm from the vas deferens, prostate, and seminal vesicles
2. sympathetic impulses
3. when sexual stimulation culminates and climaxes, sympathetic impulses from T-12 to L-2 regions pass through the genital organs, through the hypogastric and pelvic sympathetic nerve plexus to initiate emission; the impulses cause contractions from the vas deferens and the ampulla, which releases the sperm into the internal urethra and the contraction of the muscular coat of the prostrate to release prostatic fluid; contractions of the seminal vesicles follow shortly, releasing the seminal fluid and forcing the sperm forward |
|
|
Term
| What is ejaculation? What is the mechanism that causes this? |
|
Definition
1. the release of semen out of the penis
2. the filling of the urethra with semen elicits sensory signals transmitted to the pudendal nerves in the sacral regions of the cord, giving feelings of fullness in the organs; in response to sensory signals, the cord causes the rhythmic contraction of internal genital organs and ischiocavernosus and bulbocavernosus muscles, which cause an increase in the pressure in the erectile tissue of the penis, genital ducts, and urethra and it ejaculates the semen out of the penis; rhythmic thrusting of the trunk and pelvic muscles will further assist in propulsion of the semen into the vaginal tract |
|
|
Term
| What is an orgasm? How long does it last in males? What is resolution? |
|
Definition
1. the combination of emission and ejaculation
2. up to 1-2 minutes
3. resolution is the period following orgasm in which the erection ceases; this is because erection was first caused by parasympathetic stimulation, but the climax response is a sympathetic response, which cuts off parasympathetic stimulation, causing the loss of erection |
|
|
Term
| What gene essentially determines the male sex? How does it do so? |
|
Definition
1. the sex-determining region y gene (sry gene)
2. prior to its activation, the fetus has non-descript genital ridge cells which can become male or female; the sry geneencodes for testis determining factor (or the sry protein); this protein initiates a cascade of gene activations that cause the ridge cells to release testosterone (which causes other areas to differentiate as well) and differentiate into testes |
|
|
Term
| What is the default sex for humans? |
|
Definition
|
|
Term
| What is the function of the anti-Muellerian gene? |
|
Definition
| it stimulates the development of the Wolffian ducts into the male reproductive systen and the regression of the Muellerian ducts (which would otherwise develop into the fallopian tubes) |
|
|
Term
| Define androgen. Where are androgens produced? What kind of hormones are they? Steroid, peptide, eicosanoid, amine derivative, or gas? |
|
Definition
1. any hormone that has masculinizing effects
2. they are produced in the adrenal glands in small amounts (except when tumors are involved) and in the testes in large amounts
3. they are all steroids |
|
|
Term
| What is the most abundant androgen? Where is it synthesized? |
|
Definition
1. testosterone
2. the interstitial cells of Leydig, between the seminiferous tubules |
|
|
Term
| What is the importance of testosterone in fetal development? |
|
Definition
| 1. beginning the seventh week of development, testosterone secretion causes the development of male sexual characteristics (penis and scrotum); it later causes the descent of the testes into the scrotum in the last 2-3 months of fetal development (when the testes produce enough testosterone) |
|
|
Term
| After fetal development and before puberty, what is the role of testosterone? |
|
Definition
| testosterone has almost no role during this period |
|
|
Term
| What effects does testosterone have on hair throughout the body at onset of puberty? |
|
Definition
1. it causes male body hair distribution, including hair in the pubic region, along the linea alba, one the face, usually on the chest, and sometimes other regions of the body such as the back and causes hair proliferation in other regions
2. it causes hair loss in individuals with the genetic background for male-pattern baldness; DHT, a product of testosterone conversion, is the actual initiator of this |
|
|
Term
| What effect does testosterone have on skin development at onset of puberty? |
|
Definition
| it causes the development of increased skin thickness and general ruggedness as well as increased secretions by the sebaceous glands, often resulting in acne until the skin can adjust to the increase testosterone levels |
|
|
Term
| What effect does testosterone have on voice change at onset of puberty? |
|
Definition
| testosterone causes the hypertrophy of the laryngeal mucosa and enlargement of the larynx; the initial development is discordant, resulting in the "cracking" voice |
|
|
Term
| What effect does testosterone have on muscle development at onset of puberty? |
|
Definition
| testosterone can cause generally increased protein deposition and specifically causes the hypertrophy of muscles, resulting in an average of 50% more muscle mass in men than women |
|
|
Term
| What effect does testosterone have on bone development at onset of puberty? |
|
Definition
| testosterone causes increased protein deposition in bones as well and calcium deposition and retention; it also causes narrowing and lengthening of the pelvic outlet and increases its strength; large quantities of testosterone can cause increased rate of growth in bone, but it can also cause the epiphyseal plates to fuse sooner, possibly resulting in an overall stunted growth |
|
|
Term
| What effect does testosterone have on BMR as onset of puberty? |
|
Definition
| testosterone increases BMR by up to 15% for a large artificial injection and an average of 5-10% for normal natural quantities; this increase is probably due in part to the increased protein deposition |
|
|
Term
| What effect does testosterone have on RBCs at onset of puberty? |
|
Definition
| testosterone can cause an increase of some 15-20% in RBC count; the reason is unknown |
|
|
Term
| What effect does testosterone have on electrolyte and water balance at onset of puberty? |
|
Definition
| testosterone can increase sodium (and, consequently, water) reabsorption, though it does so only to a small extent; at puberty, there is some 5-10% increase in blood volume because of sodium and water retention |
|
|
Term
| Why is testosterone sometimes used to treat osteoporosis? |
|
Definition
| because testosterone can increased protein deposition (as with the collagen fibers) and increase calcium salt deposition in the bones |
|
|
Term
| What is the mechanism of action for testosterone? |
|
Definition
| testosterone diffuses through the cell (remember it is non-polar) and binds to the intracellular receptor; the complex then travels into the nucleus and binds to the nuclear receptor and, within 30 minutes, activates RNA polymerase, which increases RNA, which increases translation, which increases protein formation, which causing the various increases in BMR, protein deposition, and cell proliferation |
|
|
Term
| Where is the testosterone receptor? Cell-surface, intracellular, or nuclear? |
|
Definition
|
|
Term
| What stimulates fetal testosterone secretion? What stimulates testosterone secretion after fetal development? |
|
Definition
1. the placenta produces chorionic gonadotropin to stimulate moderate testosterone production in fetal development until 10+ weeks after birth
2. luteinizing hormone stimulates rapid testosterone production, which remains fairly steady until about 50 |
|
|
Term
| About how much of the mass of a testis is composed of interstitial Leydig cells? How do their durability compare to germinal cells? |
|
Definition
1. about 20%
2. they are more durable than germinal cells |
|
|
Term
| What are the forms that testosterone can be converted into in the tissues? What are the functions of these forms? |
|
Definition
1. in certain target organs, testosterone is converted into dihydrotestosterone (DHT), which has the same effects as testosterone but is much more potent; DHT is more prominent in organs such as the prostate (in the adult) and the external genitalia (in the fetus)
2. for testosterone that is not converted or fixed in tissues, it is converted into androsterone and dehydroepiandrosterone; these are conjugated as either glucuronides or sulfates to be excreted in the bile of the urine |
|
|
Term
| How is testosterone transported? |
|
Definition
| it travels in the blood loosely attached to albumin or tightly attached to sex hormone-binding globulin |
|
|
Term
| How long does the effect of testosterone last? |
|
Definition
| 30 minutes to several hours |
|
|
Term
| How is testosterone secretion regulated? |
|
Definition
| LH stimulates Leydig cells to secrete testosterone, which inhibits gonadotropes from secreting LH (and FSH) at the pituitary and inhibits GnRH secretion from the hypothalamus |
|
|
Term
| What is male climacteric? |
|
Definition
| with age, males have decreased sexual function, typically as a result of decreased testosterone; as sexual function decreases, the desire for intersexual relations decreases and males may experience hot flashes, feelings of suffocation, and psychotic disorders similar to those in menopause |
|
|
Term
| At what age do intersexual relations cease? |
|
Definition
| that greatly depends on the couple, but on average it ends at about 68 |
|
|
Term
| What is hypogonadism? What causes it? |
|
Definition
1. hypogonadism is a severe decrease or absence of influence from the gonads, resulting in shrunken or absent gonads
2. in men this may be caused by non-functional testes, castration, a deficiency of GnRH, or dysfunctional testosterone receptors |
|
|
Term
| What happens if the formed testes are never function? What if a male is castrated pre-puberty? What is a male is castrated post-puberty? |
|
Definition
1. the fetus develops female organs as a genetic default
2. he continues to have infantile genitals, has pre-puberty body hair distribution, maintains a childish voice, has decreased muscle mass (compared to if he wasn't castrated), has slightly increased height, decreased hair thickness and proliferation, reduced bone mass, most likely absent sex drive, and will not become bald
3. he will have the same symptoms as pre-puberty castration (with any developed male features regressing to pre-puberty features) except that penis size and voice depth regress only slightly and sexual drive will be decreased but not disappear, although ejaculation becomes unlikely due to degradation of all organs contributing to the semen due to a lack of testosterone and psychic drive provided by it |
|
|
Term
| What occurs if the hypothalamus does not secrete sufficient GnRH for adequate testosterone secretion? What is this called? |
|
Definition
1. if it occurs in fetal development, the male will develop as a female; otherwise, the male will have decreased sexual function and development and develop as a eunuch; however, this dysfunction is often linked to feeding center dysfunction, resulting in overeating and hypogonadism
2. adiposogenital syndrome, Frohlich syndrome, or hypothalamic eunuchism |
|
|
Term
| What can tumors in the interstitial Leydig cells cause? |
|
Definition
| excessive testosterone secretion; if this occurs in children, they will develop sexually quickly and have a fast but short growth spurt, with their epiphyseal plates fusing earlier, resulting in an overall stunted growth; if the tumor occurs in adults, the symptoms may be difficult to detect, due to the presence of masculine features already |
|
|
Term
| What can tumors in the germinal epithelium cause? What are they often called? |
|
Definition
1. these cells are similar to stem cells and can develop into any cell, so the tumors often develop hair, teeth, etc; occasionally the tumor develops into a tissue that secretes estrogens, causing a condition known as gynecomastia, which is an over-growth of the breasts; the tumor may also develop into placental tissue and release hCG, which will cause increases testosterone release
2. teratomas |
|
|
Term
| What is the enzyme that converts testosterone into DHT? |
|
Definition
|
|
Term
| Where is GnRH synthesized? Where is it secreted? What is its function? |
|
Definition
1. in the arcuate nucleus of the hypothalamus
2. from nerve fibers near the median eminence through the hypophyseal portal system
3. it stimulates the anterior pituitary (the gonadotropes) to synthesize and secrete LH and FSH |
|
|
Term
| What is the rate at which GnRH is secreted? How does LH's secretion compare? How does FSH's secretion compare? |
|
Definition
1. it is secreted in pulses every 1-3 hours; each pulse lasts a few minutes
2. it follows a fairly steady pulsation in response to GnRH's pulsations
3. secretion varies more with the longer-term secretion of GnRH than its pulsations |
|
|
Term
| What is believed to be the triggering factor in the initiation of puberty? |
|
Definition
| since GnRH is not secreted after birth until puberty, it is believed that its release and especially the subsequent increase in amplitude of the secretion of LH initiates puberty; the nocturnal spikes of LH secretion seem to have especial importance in the beginning of puberty |
|
|
Term
| About how much estrogen is released from the average male compared to a non-pregnant female? How is estrogen synthesized in the male reproductive system? What is the effect of estrogen in the male reproductive system? |
|
Definition
1. about 20%
2. this is unknown, but it is hypothesized that it is converted from testosterone, since other tissues (especially the liver) can convert testosterone into estrogen and androstanediol
3. it is uncertain, but it probably plays a role in spermigenesis |
|
|
Term
| How can males produce so many sperm without running out of gametes? About how many spermatogonia begin spermatogenesis per day? |
|
Definition
1. the source of the gametes, the spermagonia, are self-renewing
2. about 2M |
|
|
Term
| What is the significance of aromatase in the male reproductive system? What is its significance in obese individuals? |
|
Definition
1. aromatase can convert testosterone to estrogen in the Sertoli cells; the anti-Muellerian hormone can inhibit this activity
2. aromatase is also found in fat cells; more obese individuals may display feminine characteristics |
|
|
Term
| Which sex has a greater likelihood to develop mutation in its gametes? Why? |
|
Definition
1. females
2. because oocytes are placed in a state of arrested development, in which mutations are more likely to occur (and occur at increased frequency with age); men constantly have their spermatogonia self-renewing, dividing, and beginning meiosis and most sperm don't spend more than a month being inactive |
|
|
Term
| What is testicular feminizing syndrome? |
|
Definition
| a mutation in the androgen receptor, making it unable to respond to androgens; this is due to a mutation on the X chromosome and causes the individual to develop female genitals |
|
|
Term
| What is the pineal gland? What is its function in humans? |
|
Definition
1. it is a gland that is supposedly a vestigial remnant of a third eye located on the back of the heads of some lower animals
2. functions attributed to it include enhancing sex, staving off infection, promoting sleep, enhancing mood, and increasing longevity |
|
|
Term
| What is the function of the pineal gland in higher animals? What is its mechanism? |
|
Definition
1. in higher animals it is responsible for breeding cycle to ensure their young will be born at a time of the year with abundant food, preferred weather, etc
2. the mechanism involved the passage of light signals from the eyes to the suprachiasmal nucleus of the hypothalamus, which activates the pineal gland; the gland also releases melatonin and similar substances into the blood or through the fluid of the third ventricle and it is believed to decrease gonadotropic hormone during the winter months/hiberation periods, after which gonadotropic hormone overcomes the inhibitory effect |
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