Chapter 38 Reproduction and Development (Sections 38.5 - 38.8)

1. Chapter 38Reproduction and Development(Sections 38.5 - 38.8)

2. 38.5 Hormones and the Menstrual Cycle • Hormones coordinate cyclic changes in ovaries and uterus • Cyclic changes in the uterus (menstrual cycle) begin with the onset of menstruation • menstrual cycle • Approximately 28-day cycle in which the uterus lining thickens and then, if pregnancy does not occur, is shed • menstruation • Flow of shed uterine tissue out of the vagina

3. Phases of a Menstrual Cycle

4. Ovarian and Menstrual Cycles 1. Menstrual cycle begins: GnRH secretion by the hypothalamus causes the pituitary to increase output of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) 2. FSH stimulates an ovarian follicle to begin maturing 3. As a follicle matures, cells around the oocyte secrete estrogens (the interval of follicle maturation preceding ovulation is the follicular phase of the menstrual cycle)

5. Ovarian and Menstrual Cycles (cont.) 4 . Estrogens bind to cells of the endometrium and signal to begin cell divisions (mitosis) that thicken the endometrium 5. The pituitary detects increased level of estrogens in the blood and responds with a surge of LH production 6. The midcycle surge of LH causes the primary oocyte to complete meiosis I and undergo cytoplasmic division, and causes the follicle to swell and burst (ovulation )

6. Ovarian and Menstrual Cycles (cont.) 7. Immediately after ovulation, estrogen level declines until the corpus luteum forms (luteal phase of the cycle); it secretes some estrogen and a lot of progesterone • Estrogen and progesterone keep the hypothalamus from secreting FSH, so no other follicles can start to mature 8. Estrogens and progesterone also cause the uterine lining to thicken and encourage blood vessels to grow through it • The uterus is now prepared for a new pregnancy

7. Ovarian and Menstrual Cycles (cont.) 9. If pregnancy does not occur, the corpus luteum persists for about twelve days, then breaks down – estrogen and progesterone levels drop • The hypothalamus senses this decline, and stimulates the pituitary to increase secretion of FSH and LH • In the uterus, decline in estrogens and progesterone causes endometrial lining to break down, and menstruation begins

8. Hormones, Ovary, and Uterus

9. Hormones, Ovary, and Uterus Fig. 38.9a, p. 636

10. Hormones, Ovary, and Uterus hypothalamus GnRH anterior pituitary FSH LH A FSH and LH levels in blood 5 1 FSH LH FSH and LH stimulate follicle maturation LH surge triggers ovulation Fig. 38.9a, p. 636

11. Hormones, Ovary, and Uterus Fig. 38.9b, p. 636

12. Hormones, Ovary, and Uterus B Follicle changes in an ovary corpus luteum forms 6 corpus luteum breaks down 2 follicle matures ovulation corpus luteum secretes estrogens, progesterone follicle secretes estrogens Fig. 38.9b, p. 636

13. Hormones, Ovary, and Uterus Fig. 38.9c, p. 636

14. Hormones, Ovary, and Uterus C Estrogen and progesterone levels in blood Progesterone 7 Estrogens 3 estrogens, progesterone, cause uterine lining to thicken 9 low estrogen Fig. 38.9c, p. 636

15. Hormones, Ovary, and Uterus Fig. 38.9d, p. 636

16. Hormones, Ovary, and Uterus 8 D Changes in uterine lining menstrual flow 4 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 Days of cycle Follicular phase Luteal phase Fig. 38.9d, p. 636

17. Animation: Correlation Between Hormonal Levels and Cyclic Ovarian and Uterine Changes

18. Menstrual Disorders • Premenstrual Syndrome (PMS) • Increased aldosterone secretion stimulates reabsorption of sodium (and water) causing tissues to swell • Cycle-induced changes also cause depression, irritability, anxiety, headaches, and can disrupt sleep • Menstrual Pain • Prostaglandins stimulates uterine contractions (cramps) • Misplaced endometrial tissue (endometriosis) and benign uterine tumors (fibroids) also causes painful menstruation

19. From Puberty to Menopause • At puberty, increased estrogen secretion results in development of female secondary sexual traits (breasts) • A woman enters menopausewhen all follicles in her ovaries have either been released during a menstrual cycle or disintegrated as a result of normal aging • menopause • Permanent cessation of menstrual cycles • Hormonal changes may cause hot flashes

20. 38.6 When Egg and Sperm Meet • Egg and sperm may meet as a result of sexual intercourse • For males, intercourse requires an erection – aging, circulatory problems, and smoking affect erectile function • When a woman becomes sexually excited, glands in the cervix secret mucus, and glands on the labia produce a lubricating fluid

21. Sexual Intercourse • Intercourse increases sympathetic stimulation • Oxytocin acts on the amygdala to inhibit fear and anxiety • During orgasm, endorphins flood the brain; a surge of oxytocin causes rhythmic muscle contractions; and in males, ejaculation forces semen out of the penis

22. Fertilization • Ejaculation puts about 300 million sperm (which can live for about three days) into the vagina • Sperm swim upward into the oviduct, where fertilization of a secondary oocyte, released at ovulation, usually occurs • The secondary oocyte is covered with follicle cells over a layer of secreted proteins that form a jelly coat around it • The plasma membrane of the sperm’s head has receptors that bind species-specific proteins in the jelly

23. Fertilization (cont.) • Binding of sperm to egg proteins triggers the release of protein-digesting enzymes from the cap on the sperm’s head • Receptors in oocyte’s plasma membrane bind a sperm’s plasma membrane, the two membranes fuse, and the sperm enters the secondary oocyte • The egg’s jelly coat changes to prevent other sperm from binding

24. Fertilization (cont.) • Binding of sperm and oocyte membranes initiates meiosis II in the secondary oocyte – unequal cytoplasmic division produces a single mature egg (ovum) and a polar body • Chromosomes in the haploid egg and sperm nuclei become the genetic material of the new zygote • ovum • Mature animal egg

25. Fertilization Occurs in the Oviduct

26. Fertilization Occurs in the Oviduct Fertilization oviduct ovary Ovulation uterus opening of cervix A Fertilization most often occurs in the oviduct. Many human sperm travel swiftly through the vaginal canal into oviducts (blue arrows). Inside an oviduct, the sperm surround a secondary oocyte that was released from an ovary at ovulation. vagina sperm enter vagina Fig. 38.10a, p. 639

27. Enzymes Clear a Path for Sperm

28. Enzymes Clear a Path for Sperm follicle cell jelly layer oocyte nucleus completing meiosis II polar body B Enzymes released from the cap of each sperm clear a path through the jelly layer. Penetration of the secondary oocyte by a sperm causes the oocyte to releases substances that harden the jelly layer and prevent other sperm from binding. Fig. 38.10b, p. 639

29. Meiosis II and Fertilization

30. One Day After Fertilization

31. polar bodies haploid egg and sperm nuclei jelly layer C The oocyte nucleus completes meiosis II, and the oocyte undergoes unequal cytoplasmic division yielding a mature haploid ovum and a second polar body. The sperm’s tail and organelles degenerate, leaving only a haploid nucleus with the paternal genome. The nuclear membranes of the egg and sperm nuclei will break down and the paternal and maternal chromosomes will become arranged on a bipolar spindle in preparation for the first mitotic division of the new zygote. The photo at right is a light micrograph taken one day after fertilization. Fig. 38.10c, p. 639

32. ANIMATION: Fertilization To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

33. ANIMATION: Menstrual cycle summary To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

34. ANIMATION: Cell-mediated response To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

35. ANIMATION: Hormones and the menstrual cycle To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

36. Animation: Follicular Phase

37. Animation: Ovulation and Luteal Phase

38. ANIMATION: Implantation and Pregnancy To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

39. 38.7 Preventing Pregnancy • Couples can prevent pregnancy by avoiding sex entirely or abstaining when the woman is fertile • Hormones delivered by pills, patches, or injections can prevent a woman from ovulating • Temporary barriers such as condoms or a diaphragm keep sperm and egg apart, as do permanent surgical methods such as a vasectomy or tubal ligation

40. Common Methods of Contraception

41. BBC Video: Vaccinating Against Cancer

42. 38.8 Sexually Transmitted Diseases • Each year, pathogens that cause sexually transmitted diseases (STDs) infect about 15 million Americans • Women are more easily infected than men, have more complications, can pass an STD on to her newborn • Both men and women can be debilitated by bodywide effects of some infections

43. Bacterial Diseases • The most common bacterial STD is now chlamydia (Chlamydia trachomatis), which often causes no symptoms in women, but can infect her child • Bacteria also cause gonorrhea (infect oviducts, causing cramps, scarring, and sterility in women), and syphilis (damages liver, bones, and eventually the brain) • Bacterial STDs can be cured with antibiotics

44. Complications of Pregnancy • Tubal pregnancy • Infant with chlamydia-inflamed eyes

45. Syphilis • Skin sores caused by untreated syphilis • Syphilis is caused by Treponema pallidum, a spiral-shaped bacteria

46. Human Papillomaviruses (HPV) • HPV infection is widespread in the United States • Of about 100 HPV strains, a few cause genital warts • Some strains of HPV cause cervical cancer • Sexually active females should have an annual Pap smear to screen cells for signs of cancer • Viral diseases cannot be cured by any drug • A vaccine (Gardasil) can prevent some types of HPV infection if given before viral exposure

47. Human Immunodeficiency Virus (HIV) • Infection by HIV can cause AIDS • Unprotected anal sex is 5 times more dangerous than unprotected vaginal sex and 50 times more dangerous than oral sex • If you may have been exposed to HIV, get tested as soon as possible – early treatment may prevent development of AIDS

48. Frequency and Causes of STDs

49. Key Concepts • Human Sexual Behavior • Sexual intercourse brings together sperm and eggs, allowing fertilization • A variety of methods allow people who engage in intercourse to prevent fertilization. • Intercourse also raises the risk of infection by sexually transmitted bacteria, viruses, or protozoans