Anatomy 2 Unit 2 Critical Thinking

Describe the events and possible consequences of menopause

- A whole year without menstruation - No production of estrogen causes reproductive organs and breast tissue to atrophy, loss of bone mass, cardiovascular disorders caused by high cholesterol and low HDL - The events of menopause include a decline in estrogen production, an ovulatory ovarian cycle, and erratic menstrual periods that become shorter in length and eventually cease entirely. Possible consequences of menopause include atrophy of the reproductive organs and breasts, dryness of the vagina, painful intercourse, vaginal infections, irritability and mood changes, intense vasodilatation of the skin's blood vessels ("hot flashes"), gradual thinning of the skin, loss of bone mass, and slowly rising of the blood cholesterol levels.

Describe the hormonal events associated with the ovarian cycle.

- As follicular development proceeds, the concentration of circulating estrogen rises. Secondary follicles contain increased numbers of granulosa cells, and the level of circulating inhibin rises. The rising estrogen and inhibin levels inhibit hypothalamic secretion of GnRH and pituitary production and release of FSH. (GnRH pulse frequency is increased by estrogens and decreased by progesterone.) As the follicles develop and estrogen levels rise, the pituitary output of LH gradually increases. - Estrogens, FSH, and LH continue to support follicular development and maturation despite a gradual decline in FSH levels. In the second week of the ovarian cycle, estrogen levels sharply increase, and the tertiary follicle enlarges in preparation for ovulation. By day 14, estrogen levels peak, triggering a massive outpouring of LH from the anterior lobe of the pituitary gland. The rupture of the follicular wall results in ovulation. Next, LH stimulates the formation of the corpus luteum, which secretes moderate amounts of estrogens but large amounts of progesterone, the principal hormone of the postovulatory period. About 12 days after ovulation, declining progesterone and estrogen levels stimulate hypothalamic receptors and GnRH production increases, leading to increased FSH and LH production in the anterior lobe of the pituitary gland; the cycle begins again

In menstruation, the stratum functionalis is shed from endometrium. Explain the hormonal and physical factors responsible for shedding

- As luteinizing hormone blood levels drop, the corpus luteum begins to degenerate, resulting in a drop-in progesterone levels. In deprivation of hormonal support, the spiral arteries of the endometrium kink and go into spasms. When denied of oxygen, endometrial cells die, and as their lysosomes rupture the functional layer "self-digests".

Why is it that only one sperm out of hundreds or thousands available enter the oocyte?

- As soon as the plasma membrane of one sperm makes contact with the oocyte membrane, sodium channels open and ionic sodium moves into the oocyte from the extracellular space, causing the membrane to depolarize. This "fast block to polyspermy" prevents other sperm from fusing with the oocyte. This is followed by the cortical reaction, which constitutes the "slow block to polyspermy."

Cite two problems with a breech presentation.

- Breech presentation is buttock-first presentation. Two problems of breech presentation include a more difficult delivery and the baby's difficulty in breathing

Summarize the events that occur in sexual arousal and orgasm. Do these processes differ in male and females?

- During sexual arousal, erotic thoughts or physical stimulation of sensory nerves in the genital region increases the parasympathetic outflow over the pelvic nerve, leading to erection of the clitoris or penis. Orgasm is the intensely pleasurable sensation associated with perineal muscle contraction and ejaculation in males, and with uterine and vaginal contractions and perineal muscle contraction in females. These processes are comparable in males and females, but only males undergo emission and ejaculation.

Describe the histological composition of the uterine wall.

- Endometrium- mucosal lining. Innermost lining. Where menstruation occurs. Where an implanting embryo will develop. Stratum functionalis (functional layer) Stratum basalis (basal layer) - Myometrium- interlacing layers of smooth muscle. Thick, smooth muscle layer involved in child birth. Provides contractions - Perimetrium- Serious layer (visceral peritoneum)

During June's labor, the obstetrician decided that it was necessary to perform an episiotomy. What is an episiotomy, and why is it done?

- Episiotomy is used during child birth to aid in the process. It when a surgical cut is made at the opening of the vagina.

A 68-year-old man taking medication for hypertension complains to his physician that it has made him impotent. Explain why this could be an effect of antihypertension drugs.

- Erection is brought about by high blood pressure in the erectile tissues of the penis. Drugs that lower the blood pressure (antihypertensive medications) can thus reduce engorgement of the penis with blood.

What is the role of the clitoris in the female reproductive system?

- Female sexual organ with many nerve endings that make it sensitive to stimulation - Erectile tissue hooded by a prepuce

Only one sperm is needed to fertilize an egg, yet a man who ejaculates fewer than 10 million sperm is usually infertile. Explain this apparent contradiction. Suppose 10 million sperm were ejaculated, predict how many would come within close range of the egg. How likely is it that any one of these would fertilize it?

- Few sperm reach the egg; the more sperm there are, the higher the chance that one will fertilize the egg. - Of all of the perm, only about 100 will come near the egg, and there will be little chance that conception will occur

Describe the major structural and functional regions of a sperm

- Head: genetic region; nucleus and helmet-like acrosome containing hydrolytic enzymes that enable the sperm to penetrate an egg (DNA delivering) - Mid-piece: metabolic region; mitochondria (ATP producing) - Tail: locomotor region; flagellum

What is the function of hCG and why is it not important after the first trimester of pregnancy?

- Human chronic gonadotropin (hCG) is secreted by the trophoblast cells to encourage the corpus luteum to continue to produce progesterone and estrogen. HCG is not important past the first trimester of pregnancy because after this time, the placenta has taken over the production and secretion of these hormones.

Define menarche. What does it indicate?

- Is the first menstrual period (ages 11-13) - Occurs when the adult pattern of gonadotropin cycling is achieved

What are the main differences in gamete production between males and females?

- Males produce gametes from puberty until death; females produce gametes only from menarche to menopause. Males produce many gametes at a time; females typically produce one or two per 28-day cycle. Males release mature gametes that have completed meiosis; females release secondary oocytes held in metaphase of meiosis II.

During true labor what physiological mechanism ensures that uterine contractions continue until delivery has been completed?

- Positive feedback mechanisms between increasing levels of oxytocin and increased uterine distortion ensure that labor contractions continue until delivery has been completed.

A major symptom of endometriosis is periodic pain. Why does such pain occur?

- Regardless of their location, endometrial cells have receptors that respond to estrogen and progesterone. Under the influence of estrogen at the beginning of the menstrual cycle, any endometrial cells in the peritoneal cavity proliferate and begin to develop glands and blood vessels, which then further develop under the control of progesterone. The dramatic increase in size of this tissue presses on neighboring abdominal tissues and organs, causing periodic painful sensations.

Discuss the changes that occur in maternal systems during pregnancy. Why are these changes functionally significant?

- Respiratory rate and tidal volume increase, allowing the lungs to obtain the extra oxygen the fetus needs, and to remove the excess carbon dioxide the fetus generates. Maternal blood volume increases, compensating for blood flowing into the placenta. Nutrient and vitamin requirements increase 10-30 percent, reflecting the fact that some of the mother's nutrients go to nourish the fetus. Glomerular filtration rate increases by about 50 percent, which corresponds to the increased blood volume, and this accelerates the excretion of metabolic wastes generated by the fetus. The uterus and mammary glands increase in size, and secretory activity begins in the mammary glands.

Contraceptive pills contain progesterone and estradiol. Explain how contraceptive pills are effective?

- Slightly elevated levels of estrogen and progesterone inhibit both GnRH release at the hypothalamus and the release of FSH and LH from the anterior lobe of the pituitary gland. Without FSH, primordial follicles do not begin to develop, and levels of estrogen remain low. An LH surge, triggered by the peaking of estradiol, is necessary for ovulation to occur. If the level of estradiol is not allowed to rise above the critical level, the LH surge will not occur, and thus ovulation will not occur, even if a follicle managed to develop to a stage at which it could ovulate. Any mature follicles would ultimately degenerate, and no new follicles would mature to take their place. Although the ovarian cycle is interrupted, the level of hormones is still adequate to regulate a normal menstrual cycle.

A heavy smoker and has ignored a friend's advice to stop smoking during her pregnancy. Describe how smoking might affect the fetus.

- Smoking might cause her baby to be born underweight, addicted to nicotine, suffer from severe congenital abnormalities, or it may even cause fetal death

Why is it possible for spermatogonia to be outside the blood-testis barrier, yet necessary for primary spermatocytes and later stages to be within the barrier, isolated from the blood?

- Spermatogonia have the same diploid genome as the somatic cells of the body and therefore do not stimulate an immune response. Primary spermatocytes, however, must migrate to the other side of the blood-testis barrier before they undergo meiosis I, because meiosis I renders the cells genetically different from the somatic cells and thus capable of stimulating an immune attack if they are exposed to the blood.

Trace the pathway of a sperm from the testes to the uterine tube.

- Testis - epididymis - ductus deferens - male urethra - vagina - cervix - uterus - uterine tube

Describe the erectile tissues of the penis. How does erection occur?

- The corpora cavernosa extends along the length of the penis as far as the neck of the penis, and the erectile tissue within each corpus cavernous surrounds a central artery. The slender corpus sponges surround the urethra and extends from the superficial fascia of the urogenital diaphragm to the tip of the penis, where it expands to form the glans penis. The sheath surrounding the corpus sponges contains more elastic fibers than the corpora cavernosa, and the erectile tissue contains a pair of arteries. When parasympathetic neurons innervating the penile arteries release nitric oxide, smooth muscles in the arterial walls relax, dilating the vessels and increasing blood flow; the resulting engorgement of the vascular channels with blood causes erection of the penis.

Describe the hormonal events associated with the uterine cycle.

- The corpus luteum degenerates and progesterone and estrogen levels decrease, causing degeneration of the endometrium and the onset of menses. Next, rising levels of FSH, LH, and estrogen stimulate the repair and regeneration of the functional zone of the endometrium. During the postovulatory phase, the combination of estrogen and progesterone causes the enlargement of the uterine glands and an increase in their secretory activity.

The life span of the ovarian corpus luteum is extended for nearly three months after implantation, but otherwise it deteriorates. Explain why it is important that the corpus luteum remain functional following implantation.

- The corpus luteum must remain functional following implantation until the placenta can assume the duties of hormone production; otherwise, the endometrium will not be maintained, and the conceptus will be sloughed off in menses.

Summarize the roles of the hormones in the ovarian and uterine cycles.

- The hypothalamic secretion of GnRH triggers the pituitary secretion of FSH and LH. FSH initiates follicular development and activated follicles and ovarian interstitial cells produce estrogens. High estrogen levels stimulate LH secretion and increase anterior pituitary lobe sensitivity to GnRH, causing the release of LH. Progesterone is the main hormone of the luteal phase. Changes in estrogen and progesterone levels are responsible for maintaining the uterine cycle.

An 80-year-old man is interested in a much younger woman. Concerned because of his age, he asks his urologist if he will be able to father a child. What questions would a physician ask this man, and what diagnostic tests would be ordered.

- The man would be asked questions such as whether he has difficulty in urination or problems with impotence. The major test to be run would be to determine his sperm count.

Ben, a sexually active adolescent, appeared in the ER complaining of penile "drip" and pain during urination. An account of his recent sexual behavior was requested and recorded. What do you think Ben's problem is? What is the causative agent of his disorder? How is the condition treated, and what may happen if it isn't treated?

- The patient probably has a gonorrhea infection caused by the Neisseria gonorrhoeae bacterium. It is treated with penicillin and other antibiotics. If untreated, it can cause urethral constriction and inflammation of the entire male duct system.

Name the primary placental hormones and their functions.

- The placenta produces: 1. human chorionic gonadotropin, which maintains the integrity of the corpus luteum and promotes the continued secretion of progesterone (keeping the endometrial lining functional); 2. human placental lactogenic and placental prolactin, which help prepare the mammary glands for milk production. Human placental lactogenic also ensures adequate levels of glucose and protein for the developing fetus. 3. The placenta also produces relaxing, which increases the flexibility of the pubic symphysis, causes dilation of the cervix, and suppresses the release of oxytocin by the hypothalamus, delaying the onset of labor contractions.

After implantation, how does the developing embryo obtain nutrients? What structures and process are involved?

- The post-implantation embryo obtains nutrients through the chorionic villi and later the placenta. The placenta develops during placentation.

Whitney had both her left ovary and her right uterine tube removed surgically at age 17 because of a cyst and a tumor in these organs. Now, at 32, she remains healthy and is expecting her second child. How could Whitney conceive a child with just one ovary and one uterine tube, widely separated on opposite sides of the pelvis like this?

- There is no continuity between the ovary and the uterine tube and the secondary oocytes are released into the peritoneal cavity. The ovulated oocyte is coaxed into the uterine tube by the activity of the fimbriae and tubal cilia. Though it is a longer journey, oocytes released on one side of the peritoneal cavity could ultimately enter the uterine tube on the opposite side

Women with eating disorders and female bodybuilders commonly experience amenorrhea.

- These observations suggest that a certain amount of body fat is necessary for menstrual cycles to occur. The nervous system appears to respond to circulating levels of the adipose tissue hormone leptin; when leptin levels fall below a certain set point, menstruation ceases. Because a woman lacking adequate fat reserves might not be able to have a successful pregnancy, the body prevents pregnancy by shutting down the ovarian cycle, and thus the menstrual cycle. Once sufficient energy reserves become available, the cycles begin again.

Tiffany, a 46-year-old mother of six children, visited her physician complaining of a "bearing down" sensation in her pelvis, low backache, and urinary incontinence. A vaginal examination showed that the external of her cervix was just inside the vaginal orifice and her perineum exhibited large keloids. Her history revealed that she was a member of a commune that shunned hospital births (if at all possible). What do you think Tiffany's problem is and what caused it? (Be anatomically specific.)

- This patient has a prolapsed uterus, no doubt caused by the stress on the pelvic floor muscles during her many pregnancies. She also has keloids, one can assume that the central tendon to which those muscles attach has been severely damaged, and many vaginal tears have occurred

Why might this peritonitis occur more readily in females than in males?

- Women more frequently experience peritonitis stemming from a urinary tract infection because infectious organisms exiting the urethral orifice can readily enter the nearby vagina. From there, they can then proceed to the uterus, into the uterine tubes, and finally into the peritoneal cavity. No such direct path of entry into the abdominopelvic cavity exists in men.

Describe each of three phases of a typical 28-day menstrual cycle.

1. Menses, the interval marked by the degeneration and loss of the functional zone of the endometrium, lasts 1-7 days, and 35-50 mL (1.2-1.7 oz.) of blood is lost. 2. The proliferative phase features growth and vascularization resulting in the complete restoration of the functional zone; it lasts from the end of menses until the beginning of ovulation, around day 14. 3. During the secretory phase, the uterine glands enlarge, accelerating their rates of secretion, and the arteries elongate and spiral through the tissues of the functional zone; this phase begins at ovulation, occurs under the combined stimulatory effects of progesterone and estrogens from the corpus luteum, and persists as long as the corpus luteum remains intact.

A 36-year-old mother of four is considering tubal ligation to ensure that her family gets no larger. She asks the physician if she will become "menopausal" after the surgery. a. How would you answer her question and explain away her concerns? b. Explain what a tubal ligation is.

a. No, she will not be menopausal, her ovaries will not be affected by this procedure. they will continue to produce hormones b. tubal ligation is the cutting of the uterine tubes