Chapter 17 Reproductive Systems

Name and describe the functions of the three regions of a sperm cell.

- head; contains the DNA and is covered by the acrosome, an enzyme-rich cap that helps egg penetration. - midpiece; contains mitochondria to power the tail for locomotion. - tail; locomotion to the egg.

Name the male accessory glands and give their functions.

- seminal vesicles; secrete most of the seminal fluids. - prostate gland; secretes watery alkaline fluid, which activates sperm and raises the vaginal pH. - bulbourethral glands; secrete lubricating mucus.

List the hormones from the hypothalamus, the anterior pituitary gland, and the testes that are important in the control of sperm production. Explain the interactions between these hormones.

- testosterone; produced in the testes. Testosterone is necessary for the maturation of sperm. When testosterone levels in the blood fall, the hypothalamus is stimulated to release GnRH. - GnRH; produced in the hypothalamus, stimulates the anterior pituitary to release LH and FSH. - LH; produced in the anterior pituitary; stim- ulates the testes to produce testosterone. - FSH; produced in the anterior pituitary; stim- ulates sperm production (with testosterone).

Describe a vasectomy and a tubal ligation

A vasectomy includes making incisions in the scrotum and sealing off each vas deferens so that sperm cannot enter the urethra. A tubal ligation includes cutting and sealing each oviduct so that the egg cannot reach the uterus and the sperm cannot reach the egg.

What is an IUD?

An intrauterine device that can remain in the uterus for several years. It prevents pregnancy by interfering with fertilization and implantation.

Why is an ectopic pregnancy dangerous to the mother health?

Because the oviduct cannot expand as the uterus does to accommodate embryonic growth, the oviduct may rupture, causing the mother to hemorrhage, which can be fatal.

How does the combination birth control pill reduce the chances of pregnancy?

Birth control pills contain the hormones estro- gen and progesterone, which inhibit the produc- tion of FSH and LH. This prevents the follicles from maturing, as well as preventing ovulation if a follicle should develop.

Which is the correct pairing of a structure with its function?

Corpus luteum; production of estrogen and progesterone

Describe the interplay of hormones from the anterior pituitary and from the ovaries that is responsible for the menstrual cycle.

Day 1 of the menstrual cycle is considered the first day of menstrual flow. At this point in the cycle, estrogen and progesterone levels are low, and a new follicle is beginning to develop. FSH from the ante- rior pituitary stimulates estrogen production by the developing follicle. As the follicle develops, estrogen levels rise and cause cell division in the endometrium, which thickens the endometrium for implantation of an embryo. As the follicle approaches maturity, the rapidly rising level of estro- gen stimulates LH release from the anterior pitu- itary, which triggers ovulation. The follicle cells remaining in the ovary after ovulation are trans- formed into an endocrine structure, called the cor- pus luteum, that produces estrogen and progesterone. The estrogen continues to stimulate cell division in the endometrium, and progesterone causes the development of mucous glands that will nourish the embryo if one forms. Progesterone is also needed to maintain the endometrium. If preg- nancy does not occur, the corpus luteum degener- ates, and the level of estrogen and progesterone decrease. Without progesterone to maintain the endometrium, it decreases and the endometrium is no longer maintained. The endometrium breaks down and is lost as menstrual fluid.

What are the stages of the human sexual response?

Excitement, plateau, orgasm, and resolution.

Name the male and female gonads. What are the functions of these organs?

The male gonads are testes, and the female gonads are the ovaries. They both function to pro- duce gametes (eggs and sperm) and sex hormones. The ovaries produce eggs and the hormones estro- gen and progesterone. The testes produce sperm and the hormone testosterone.

What is menopause? Why does menopause lower estrogen levels? What are some effects of lowered estrogen levels?

Menopause is the cessation of the menstrual cycle and ovulation, because follicles are no longer developing. From the moment of birth, the number of primary follicles in a woman's ovaries begins to decrease. By the time she is about 45 to 55 years old, follicles remaining in the ovaries no longer respond to FSH and develop. Without egg develop- ment, ovulation cannot occur. Without the cycling of hormones, the menstrual cycle does not occur.

How do progesterone-only means of contraception reduce the risk of pregnancy?

Use of progesterone only means of contraception does not prepare the endometrium for embryo implantation and may prevent ovulation.

What is an ectopic pregnancy?

Occurs if the embryo implants in a place other than the uterus.

After sperm are released in the female reproductive system, they can move to the egg and fertilize it. Which is the correct order of structures through which the sperm will pass?

Vagina, cervix, body of uterus, oviduct

The interstitial cells secrete ?

Secrete testosterone.

What health risks are associated with use of the birth control pill?

Side effects of using the birth control pill may include acne and headaches. More serious side effects include high blood pressure and blood clots, which could lead to heart attack, stroke, or pulmonary embolism.

This is correct about semen.

Sperm cells make up most of the volume of semen.

How is the temperature maintained in the testes? Why is tem- perature control important?

Temperature regulation in the testes depends on a muscle that contracts to bring the testes closer to the body for warmth when scrotal temperature is low or relaxes when the scrotal temperature is high, so the testes are farther away from the body. Sperm develop better in the testes at a few degrees lower than body temperature.

Describe the structure of female breasts. What is their function?

The breasts contain milk glands that produce milk for offspring. The milk glands are connected to ducts that lead to the outside environment at the nipple. Most of the breast consists of fatty tissue.

What is the function of the penis in reproduction? Describe the process by which the penis becomes erect.

The function of the penis is to deliver sperm to the vagina. The penis becomes erect when neural activity dilates arterioles in the penis, allowing blood to enter the spongy tissue and causing the veins to drain less blood. The change in blood dis- tribution allows blood to accumulate in the spongy tissue and cause an erection.

What are the two main layers in the wall of the uterus?

The inner layer is the endometrium, which is the lining that builds up each month in preparation for pregnancy. These preparations include cell division to thicken the endometrium, which is stimulated by estrogen, and an increase in glandular activity to nourish the embryo, which is stimulated by progesterone. The outer layer is the myometrium, which consists of smooth muscle. The myometrium allows the uterus to get larger as the fetus grows and provides the force to push the baby out during delivery.

How do the diaphragm, male condom, and female condom prevent pregnancy?

They prevent pregnancy by preventing the sperm from reaching the egg.

Sperm are stored and mature in the?

epididymis

12. Describe the ovarian cycle. Include in your description primary oocytes, primary follicles, mature Graafian follicles, and the corpus luteum.

he ovarian cycle starts with a primary follicle, which is a primary oocyte surrounded by a layer of follicle cells. As the primary follicle matures, the fol- licle cells divide and produce estrogen, which enters the bloodstream and accumulates in a fluid within the follicle. The accumulation of fluid causes the layer of follicle cells to split, and the fluid continues to accumulate in the newly formed cavity. The estrogen in the fluid causes the first meiotic division in the primary oocyte, forming a secondary oocyte. Estrogen-containing fluid continues to accumulate as the follicle grows. Eventually, the mature Graafian follicle forms. The Graafian follicle con- tains a secondary oocyte that is located at the edge and surrounded by follicle cells and a large fluid- filled cavity. At ovulation, the mature follicle pops, releasing the egg. The follicle cells remaining in the ovary are transformed into an endocrine structure called the corpus luteum, which secretes estrogen and progesterone. If pregnancy does not occur the corpus luteum will degenerate within about 2 weeks.

The controversial pill Mifepristone (formerly called RU486) works to terminate a pregnancy by preventing progesterone from acting. This effect would cause an abortion because prog- esterone is needed to...?

maintain the endometrium.

List the major structures of the female reproductive system and give their functions

ovaries—produce the eggs. oviducts—path for egg/early embryo to travel to uterus. uterus—site for implantation of the embryo and development of the fetus. vagina—birth canal.

Fertilization usually occurs in the?

oviduct

Trace the path of sperm from their site of production to their release from the body, naming each tube the sperm pass through. p. 333

seminiferous tubules : epididymis : vas deferens : urethra.