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Chapter 21: Reproductive System

Chapter 21: Reproductive System. 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. The male reproductive system. Fig. 21.1.

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Chapter 21: Reproductive System

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  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. At ejaculation: sperm leave the testes vas deferens ejaculatory ductsurethra.

  4. Testes Fig. 21.3 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.

  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

  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. 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).

  10. Female Hormone Levels • The Ovarian Cycle • 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. Follicular phase (day 1-13) Ovulation occurs on day 14 of a 28-day cycle Luteal phase (days 15–28) Two Phases of a 28-day Ovarian Cycle

  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) 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 +

  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 Menses Proliferative Secretory

  17. Fertilization and Pregnancy • If fertilization occurs, the embryo implants in the endometrium. • No new ovulations occur during this time.

  18. Implantation • Placentahuman chorionic gonadotropin (HCG) • corpus luteum and uterine lining maintained. • Eventually, the placenta will produce sufficient estrogen and progesterone.

  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.

  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.

  22. Contraceptive implants use time-release progesterone, and Depo-Provera injections alter the endometrium to discourage pregnancy. Contraceptivevaccines may be able to utilize the immune system to HCG that is necessary to maintain the embryo. Fig. 22.12

  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.

  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: • www.cdc.gov

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

  29. Reproduction of HIV

  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 highlyactive antiretroviral therapy (HAART) stops the progress of AIDS in the chronic stage for a number of years.

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

  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.

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