1. Chapter 21: Reproductive System

2. Male Reproductive System
Testes (male gonads) produce sperm, which mature in the epididymis.
Gland secretions contain fructose for energy, so sperm can swim.
Sperm with secretions from glands is called semen.

3. The male reproductive system
Fig. 21.1
Secretions are added by three glands: seminal vesicles, prostate gland, and bulbourethral gland.
The testes produce sperm. The seminal vesicles, the prostate gland, and the bulbourethral glands provide a fluid medium for the sperm. Circumcision is the removal of the foreskin. Notice that the penis in this diagram is not circumcised, because the foreskin is present. Table 21.1 (page 415) summarizes the organs of the male reproductive system and their functions.
At ejaculation: sperm leave the
testes  vas deferens  ejaculatory ducts  urethra.

4. Testes
Fig. 21.3
The lobules of the testes contain seminiferous tubules. On the right, a light micrograph of the seminiferous tubules shows interstitial cells occurring in clumps among the seminiferous tubules.
Seminiferous tubules (surrounded by testosterone producing interstitial cells) produce haploid sperm through spermatogenesis (meiosis).
Sustentacular cells (Sertoli cells) support, nourish, and regulate the cells during spermatogenesis.

5. Sperm anatomy
Stores enzymes needed to penetrate the egg
Fig. 21.3
Sperm do not live more than 48 hours in the female genital tract.
A sperm has a head, a middle piece, and a tail. The nucleus is located in the head, which is capped by the acrosome containing enzymes.

6. Hormonal Regulation in Males
Gonadotropin-releasing hormone (GnRH)
follicle-stimulating hormone (FSH) and
luteinizing hormone (LH).
Inhibin
Testosterone
 = ‘stimulates the release of’

7. Hormonal control of testes
Fig. 21.4
Negative feedback + +
GnRH (gonadotropin-releasing hormone) stimulates the anterior pituitary to secrete the gonadotropic hormones: FSH stimulates the production of sperm, and LH stimulates the production of testosterone. Testosterone and inhibin exert negative feedback control over the hypothalamus and the anterior pituitary, and this regulates the level of testosterone in the blood.

8. Female Reproductive System
Ovaries (female gonads) usually produce one egg (or ovum) per month by oogenesis.
Ovulation is the release of the egg from the ovary as it enters an oviduct.

9. The female reproductive tract
Fig. 21.5
The female reproductive tract
Fimbriae sweep the egg into an oviduct with the help of cilia.
Fertilization usually takes place in the oviduct
Zygote moves to the uterus, where it implants in the uterine lining (endometrium).
The ovaries release one egg a month; fertilization occurs in the oviduct, and development occurs in the uterus. The vagina is the birth canal as well as the organ of sexual intercourse.
Table 21.2 (page 418) lists the organs of the female reproductive tract along with their functions.

10. The Ovarian Cycle Female Hormone Levels
A female is born with up to 2 million ovarian follicles (with immature oocytes) that reduce to 300,000–400,000 by puberty, but only 400 follicles mature at the rate of one egg per monthly cycle.

11. Two Phases of a 28-day Ovarian Cycle
Follicular phase (day 1-13)
Ovulation occurs on day 14 of a 28-day cycle
Luteal phase (days 15–28)
As the luteal phase comes to an end, menstruation occurs.

12. Anatomy of ovary and follicle
Fig. 21.7
Egg follicles mature, from primary follicles to Graafian follicles.
When the egg is released, the empty follicle becomes the hormone-secreting corpus luteum.
Follicular Phase (days 1-13)
As a follicle matures, the oocyte enlarges and is surrounded by layers of follicular cells and fluid. Eventually, ovulation occurs, the mature follicle ruptures, and the secondary oocyte is released. A single follicle actually goes through all stages in one place within the ovary.
Primary follicles contain the oocyte and begin producing the sex hormone estrogen.
Secondary follicles contain the secondary oocyte and produce the sex hormones estrogen and some progesterone.
The vesicular (Graafian) follicle develops.
Ovulation: The secondary oocyte is released.
The corpus luteum produces the sex hormones progesterone and some estrogen.
The corpus luteum degenerates.
Luteal Phase
(days 15-28)
Ovulation (day 14)

13. Hormonal Regulation in Females Gonadotropin-releasing hormone (GnRH)
follicle-stimulating hormone (FSH) and
luteinizing hormone (LH).
Estrogen
Progesterone
 = ‘stimulates the release of’

14. Hormonal control of ovaries
Fig. 21.8
Estrogen by itself = Positive Feedback
Negative Feedback +
The hypothalamus produces GnRH (gonadotropin-releasing hormone). GnRH stimulates the anterior pituitary to produce FSH (follicle-stimulating hormone) and LH (luteinizing hormone). FSH stimulates the follicle to produce estrogen, and LH stimulates the corpus luteum to produce progesterone. Estrogen and progesterone maintain the sexual organs (e.g., uterus) and the secondary sex characteristics, and exert feedback control over the hypothalamus and the anterior pituitary.

15. The Uterine Cycle Menstruation (days 1-5)
Proliferative phase (days 6-13)
Ovulation occurs about day 14
Secretory phase (days 15-28)

16. Female hormone levels
Estrogen and progesterone affect the endometrium and control the uterine cycle.
During menstruation, menses occurs due to the low levels of estrogen and progesterone.
Fig. 21.9
During the follicular phase of the ovarian cycle, FSH released by the anterior pituitary promotes the maturation of a follicle in the ovary. The ovarian follicle produces increasing levels of estrogen, which causes the endometrium to thicken during the proliferative phase of the uterine cycle. After ovulation and during the luteal phase of the ovarian cycle, LH promotes the development of the corpus luteum. This structure produces increasing levels of progesterone, which causes the endometrial lining to become secretory. Menses due to the breakdown of the endometrium begins when progesterone production declines to a low level.
Menses Proliferative Secretory

17. Fertilization and Pregnancy
If fertilization occurs, the embryo implants in the endometrium.
No new ovulations occur during this time.
The placenta originates from both fetal and maternal tissues.

18. Implantation Placenta  human chorionic gonadotropin (HCG)
corpus luteum and uterine lining maintained.
Eventually, the placenta will produce sufficient estrogen and progesterone.
A scanning electron micrograph showing an embryo implanted in the endometrium on day 12 following fertilization.

19. Estrogen and Progesterone
Are important in:
-Development of sex organs
-Maintenance of the secondary sex characteristics.

20. Menopause
Between the ages of 45 and 55, the ovarian and uterine cycles cease.
The ovaries are no longer responsive to anterior pituitary hormones (FSH and LH), and thus no longer produce estrogen and progesterone.
When menstruation ceases for a year, menopause is complete.
Some women experience unpleasant symptoms during menopause, including hot flashes, insomnia, headaches, dizziness, and depression.

21. Control of Reproduction
Contraceptives are medications and devices that reduce the chance of pregnancy.
Birth control pills – simulates pregnancy levels of estrogen and progesterone
Intrauterine device (IUD) - alters the uterine environment
Diaphragm - is a latex barrier that covers the cervix - must be used along with spermicidal jelly or cream
Condom - a latex sheath fitted over the erect penis.
Table 21.4 (page 426) lists the most frequently used birth-control methods.

22. Contraceptive implants use time-release progesterone, and Depo-Provera injections alter the endometrium to discourage pregnancy.
Contraceptive vaccines may be able to utilize the immune system to HCG that is necessary to maintain the embryo.
Fig

23. Morning-after Pills
A kit called Preven, may be taken up to 72 hours after unprotected intercourse and upsets the normal uterine cycle, making implantation unlikely.
Mifepristone (RU-486) is a pill that causes the loss of an implanted embryo and may one day be routinely taken if menstruation is late.

24. Infertility
Infertility is the failure of a couple to achieve pregnancy after one year of regular, unprotected intercourse.

25. Causes of Infertility
Endometriosis, growth of the uterine lining outside the uterus, or blocked oviducts due to pelvic inflammatory disease (PID).
Low sperm count and/or production of abnormal sperm occur due to disease, radiation, chemicals, high testes temperature, or psychoactive drugs.
Endometriosis occurs when the menstrual discharge flows up into the oviducts and out into the abdominal cavity. This backward flow allows living uterine cells to establish themselves in the uterine cavity, where they go through the uterine cycle, causing pain and structural abnormalities that make it more difficult for a woman to conceive.
The success rate for vasectomy reversal is only about 40%.
Sometimes the causes of infertility can be corrected by giving the female fertility drugs, which are gonadotropic hormones that stimulate the ovaries and bring about ovulation. Such hormone treatments may cause multiple ovulations and higher-order multiple births.

26. Assisted Reproductive Technologies
Alternative methods to assist reproduction include artificial insemination by donor and intrauterine insemination, in vitro fertilization, and gamete intrafallopian transfer (GIFT), intracytoplasmic sperm injection, and surrogate mothers who carry a pregnancy for another couple.

27. Sexually Transmitted Diseases
Sexually transmitted diseases (STDs) are viral or bacterial in origin and are transmitted through sexual contact.
The STDs caused by bacteria can be treated with antibiotics, but those caused by viruses cannot.
The body does not become immune to STDs.
Center for Disease Control and Prevention:

28. AIDS
Acquired immunodeficiency syndrome (AIDS) is caused by the retrovirus HIV whose primary host is helper T cells.

29. Reproduction of HIV
HIV is a retrovirus that utilizes reverse transcription to produce viral DNA. Viral DNA integrates into the cell’s chromosomes before it reproduces and buds from the cell.

30. Phases of an HIV Infection
During Category A: Acute Phase, the CD4 T lymphocyte count is 500 per mm3 or greater.
By the Category B: Chronic phase, the CD4 T cell count is 200–499 per mm3.
By the Category C: AIDS stage, the CD4 T cell count is below 200 per mm3.

31. Treatment for HIV
There is no cure for AIDS but highly active antiretroviral therapy (HAART) stops the progress of AIDS in the chronic stage for a number of years.
The drug AZT is a reverse transcriptase inhibitor.
A pregnant woman who is infected with HIV and takes reverse transcriptase inhibitors during her pregnancy reduces the chance of HIV transmission to her newborn by nearly 66%.
Preventing the transmission of HIV is the subject of the Health Focus on page 432.

32. Other STD’s Genital herpes  herpes simplex virus type 2
Genital warts  human papillomaviruses (HPVs).
Gonorrhea  by the bacterium Neisseria gonorrhoeae.
Syphilis  by the bacterium Treponema pallidum

33. Hepatitis Infections There are a number of hepatitis infections.
Hepatitis A (viral infection) is normally acquired from drinking sewage-contaminated water, but may also be spread through oral/anal contact.
Hepatitis B is spread by sexual contact.
Hepatitis C is spread through transfusion.
Still other types of hepatitis are under investigation.

34. Chlamydia
Chlamydia (bacterium Chlamydia trachomatis) infections are more numerous than any other sexually transmitted disease.
Symptoms may appear to be a urinary tract infection with a mild burning sensation upon urination.
If a newborn is exposed to chlamydia during delivery, inflammation of the eyes or pneumonia can result. It is possibl that chlamydial infections increase the possibility of premature births and stillbirths.