1. LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick Animal Reproduction Chapter 46

2. Overview: Pairing Up for Sexual Reproduction Each sea slug produces sperm and eggs; in a few weeks, new individuals will hatch from fertilized eggs Animal reproduction takes many forms A population outlives its member only by reproduction, the generation of new individuals from existing ones © 2011 Pearson Education, Inc.

3. Figure 46.1

4. Concept 46.1: Both asexual and sexual reproduction occur in the animal kingdom Sexual reproduction is the creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote Asexual reproduction is creation of offspring without the fusion of egg and sperm © 2011 Pearson Education, Inc.

5. Mechanisms of Asexual Reproduction Many invertebrates reproduce asexually by fission, separation of a parent into two or more individuals of about the same size © 2011 Pearson Education, Inc.

6. Video: Hydra Budding

7. Figure 46.2

8. In budding, new individuals arise from outgrowths of existing ones Fragmentation is breaking of the body into pieces, some or all of which develop into adults Fragmentation must be accompanied by regeneration, regrowth of lost body parts Parthenogenesis is the development of a new individual from an unfertilized egg © 2011 Pearson Education, Inc.

9. Sexual Reproduction: An Evolutionary Enigma Sexual females have half as many daughters as asexual females; this is the “twofold cost” of sexual reproduction Despite this, almost all eukaryotic species reproduce sexually © 2011 Pearson Education, Inc.

10. Figure 46.3-1 Asexual reproduction Female Sexual reproduction Generation 1 Female

11. Figure 46.3-2 Asexual reproduction Female Sexual reproduction Generation 1 Female Male Generation 2

12. Figure 46.3-3 Asexual reproduction Female Sexual reproduction Generation 1 Female Male Generation 3 Generation 2

13. Figure 46.3-4 Asexual reproduction Female Sexual reproduction Generation 1 Female Male Generation 4 Generation 3 Generation 2

14. Sexual reproduction results in genetic recombination, which provides potential advantages –An increase in variation in offspring, providing an increase in the reproductive success of parents in changing environments –An increase in the rate of adaptation –A shuffling of genes and the elimination of harmful genes from a population © 2011 Pearson Education, Inc.

15. Reproductive Cycles Ovulation is the release of mature eggs at the midpoint of a female cycle Most animals exhibit reproductive cycles related to changing seasons Reproductive cycles are controlled by hormones and environmental cues Because seasonal temperature is often an important cue in reproduction, climate change can decrease reproductive success © 2011 Pearson Education, Inc.

16. Figure 46.4

17. Some organisms can reproduce sexually or asexually, depending on conditions Several genera of fishes, amphibians, and lizards reproduce only by a complex form of parthenogenesis that involves the doubling of chromosomes after meiosis Asexual whiptail lizards are descended from a sexual species, and females still exhibit mating behaviors © 2011 Pearson Education, Inc.

18. Figure 46.5 (a) A. uniparens females (b) The sexual behavior of A. uniparens is correlated with the cycle of ovulation. Estradiol Ovulation Progesterone Time Female Male- like Behavior Hormone level Ovary size

19. Figure 46.5a (a) A. uniparens females

20. Figure 46.5b (b) The sexual behavior of A. uniparens is correlated with the cycle of ovulation. Estradiol Ovulation Progesterone Time Female Male- like Behavior Hormone level Ovary size

21. For many animals, finding a partner for sexual reproduction may be challenging One solution is hermaphroditism, in which each individual has male and female reproductive systems Two hermaphrodites can mate, and some hermaphrodites can self-fertilize © 2011 Pearson Education, Inc. Variation in Patterns of Sexual Reproduction

22. Individuals of some species undergo sex reversals Some species exhibit male to female reversal (for example, certain oysters), while others exhibit female to male reversal (for example, a coral reef fish) © 2011 Pearson Education, Inc.

23. Concept 46.2: Fertilization depends on mechanisms that bring together sperm and eggs of the same species The mechanisms of fertilization, the union of egg and sperm, play an important part in sexual reproduction In external fertilization, eggs shed by the female are fertilized by sperm in the external environment © 2011 Pearson Education, Inc.

24. Video: Hydra Releasing Sperm

25. In internal fertilization, sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract Internal fertilization requires behavioral interactions and compatible copulatory organs All fertilization requires critical timing, often mediated by environmental cues, pheromones, and/or courtship behavior © 2011 Pearson Education, Inc.

26. Figure 46.6

27. Ensuring the Survival of Offspring Internal fertilization is typically associated with production of fewer gametes but the survival of a higher fraction of zygotes Internal fertilization is also often associated with mechanisms to provide protection of embryos and parental care of young © 2011 Pearson Education, Inc.

28. The embryos of some terrestrial animals develop in eggs with calcium- and protein-containing shells and several internal membranes Some other animals retain the embryo, which develops inside the female In many animals, parental care helps ensure survival of offspring © 2011 Pearson Education, Inc.

29. Figure 46.7

30. Gamete Production and Delivery To reproduce sexually, animals must produce gametes In most species individuals have gonads, organs that produce gametes Some simple systems do not have gonads, but gametes form from undifferentiated tissue More elaborate systems include sets of accessory tubes and glands that carry, nourish, and protect gametes and developing embryos © 2011 Pearson Education, Inc.

31. Most insects have separate sexes with complex reproductive systems In many insects, the female has a spermatheca in which sperm is stored during copulation © 2011 Pearson Education, Inc.

32. Figure 46.8 (a) Male fruit fly (b) Female fruit fly Accessory gland Ejaculatory duct Penis and claspers Testis Vas deferens Seminal vesicle Ovary Accessory gland Oviduct Spermatheca Uterus Vulva

33. Figure 46.8a (a) Male fruit fly Accessory gland Ejaculatory duct Penis and claspers Testis Vas deferens Seminal vesicle

34. Figure 46.8b (b) Female fruit fly Ovary Accessory gland Oviduct Spermatheca Uterus Vulva

35. A cloaca is a common opening between the external environment and the digestive, excretory, and reproductive systems A cloaca is common in nonmammalian vertebrates; mammals usually have a separate opening to the digestive tract © 2011 Pearson Education, Inc.

36. Monogamy is relatively rare among animals Males and/or females of some species have evolved mechanisms to decrease the chance of their mate mating with another individual Females can sometimes influence the relative reproductive success of their mates © 2011 Pearson Education, Inc.

37. Figure 46.9 RESULTS Control; not remated Remated to wild-type males Remated to “no-sperm” males Remated to “no-ejaculate” males 30 20 10 0 Percentage of females lacking sperm in spermatheca

38. Concept 46.3: Reproductive organs produce and transport gametes The following section focuses on the human reproductive system © 2011 Pearson Education, Inc.

39. Female Reproductive Anatomy The female external reproductive structures include the clitoris and two sets of labia The internal organs are a pair of gonads and a system of ducts and chambers that carry gametes and house the embryo and fetus © 2011 Pearson Education, Inc.

40. Animation: Female Reproductive Anatomy Right-click slide / select “Play”

41. Figure 46.10 (Rectum) Cervix Vagina Major vestibular (Bartholin’s) gland Vaginal opening Oviduct Ovary Uterus (Urinary bladder) (Pubic bone) Urethra Body Glans Prepuce Clitoris Labia minora Labia majora Ovaries Oviduct Follicles Corpus luteum Uterine wall Endometrium Vagina Uterus Cervix

42. Figure 46.10a (Rectum) Cervix Vagina Major vestibular (Bartholin’s) gland Vaginal opening Oviduct Ovary Uterus (Urinary bladder) (Pubic bone) Urethra Body Glans Prepuce Clitoris Labia minora Labia majora

43. Figure 46.10b Ovaries Oviduct Follicles Corpus luteum Uterine wall Endometrium Vagina Uterus Cervix

44. Ovaries The female gonads, the ovaries, lie in the abdominal cavity Each ovary contains many follicles, which consist of a partially developed egg, called an oocyte, surrounded by support cells Once a month, an oocyte develops into an ovum (egg) by the process of oogenesis © 2011 Pearson Education, Inc.

45. Ovulation expels an egg cell from the follicle, the cells of which produce estradiol prior to ovulation The remaining follicular tissue grows within the ovary, forming a mass called the corpus luteum The corpus luteum secretes estradiol and progesterone that helps to maintain pregnancy If the egg is not fertilized, the corpus luteum degenerates © 2011 Pearson Education, Inc.

46. Oviducts and Uterus The egg cell travels from the ovary to the uterus via an oviduct, or fallopian tube Cilia in the oviduct convey the egg to the uterus, also called the womb The uterus lining, the endometrium, has many blood vessels The uterus narrows at the cervix, then opens into the vagina © 2011 Pearson Education, Inc.

47. Vagina and Vulva The vagina is a thin-walled chamber that is the repository for sperm during copulation and serves as the birth canal The vagina opens to the outside at the vulva, which consists of the labia majora, labia minora, hymen, and clitoris © 2011 Pearson Education, Inc.

48. The clitoris has a head called a glans covered by the prepuce The vagina, labia minora, and clitoris are rich with blood vessels; the clitoris also has many nerve endings © 2011 Pearson Education, Inc.

49. Mammary Glands The mammary glands are not part of the reproductive system but are important to mammalian reproduction Within the glands, small sacs of epithelial tissue secrete milk © 2011 Pearson Education, Inc.

50. Male Reproductive Anatomy The male’s external reproductive organs are the scrotum and penis Internal organs are the gonads, which produce sperm and hormones, and accessory glands © 2011 Pearson Education, Inc.

51. Animation: Male Reproductive Anatomy Right-click slide / select “Play”

52. Seminal vesicle (behind bladder) Urethra Scrotum (Urinary bladder) Prostate gland Bulbourethral gland Erectile tissue of penis Vas deferens Epididymis Testis Seminal vesicle (Rectum) Vas deferens Ejaculatory duct Prostate gland Bulbourethral gland Vas deferens Epididymis Testis Scrotum (Urinary bladder) (Urinary duct) (Pubic bone) Erectile tissue Urethra Glans Prepuce Penis Figure 46.11

53. Figure 46.11a Seminal vesicle (behind bladder) Urethra Scrotum (Urinary bladder) Prostate gland Bulbourethral gland Erectile tissue of penis Vas deferens Epididymis Testis

54. Figure 46.11b Seminal vesicle (Rectum) Vas deferens Ejaculatory duct Prostate gland Bulbourethral gland Vas deferens Epididymis Testis Scrotum (Urinary bladder) (Urinary duct) (Pubic bone) Erectile tissue Urethra Glans Prepuce Penis

55. Testes The male gonads, or testes, consist of highly coiled tubes surrounded by connective tissue Sperm form in these seminiferous tubules Leydig cells produce hormones and are scattered between the tubules Production of normal sperm cannot occur at the body temperatures of most mammals © 2011 Pearson Education, Inc.

56. The testes of many mammals are held outside the abdominal cavity in the scrotum, where the temperature is lower than in the abdominal cavity © 2011 Pearson Education, Inc.

57. Ducts From the seminiferous tubules of a testis, sperm pass into the coiled tubules of the epididymis During ejaculation, sperm are propelled through the muscular vas deferens and the ejaculatory duct, and then exit the penis through the urethra © 2011 Pearson Education, Inc.

58. Accessory Glands Semen is composed of sperm plus secretions from three sets of accessory glands The two seminal vesicles contribute about 60% of the total volume of semen The prostate gland secretes its products directly into the urethra through several small ducts The bulbourethral glands secrete a clear mucus before ejaculation that neutralizes acidic urine remaining in the urethra © 2011 Pearson Education, Inc.

59. Penis The human penis is composed of three cylinders of spongy erectile tissue During sexual arousal, the erectile tissue fills with blood from the arteries, causing an erection The head of the penis has a thinner skin covering than the shaft and is more sensitive to stimulation © 2011 Pearson Education, Inc.

60. Gametogenesis Gametogenesis, the production of gametes, differs in male and female, reflecting the distinct structure and function of their gametes Sperm are small and motile and must pass from male to female Eggs are larger and carry out their function within the female © 2011 Pearson Education, Inc.

61. Spermatogenesis, the development of sperm, is continuous and prolific (millions of sperm are produced per day; each sperm takes about 7 weeks to develop Oogenesis, the development of a mature egg, is a prolonged process Immature eggs form in the female embryo but do not complete their development until years or decades later © 2011 Pearson Education, Inc.

62. Spermatogenesis differs from oogenesis in three ways –All four products of meiosis develop into sperm while only one of the four becomes an egg –Spermatogenesis occurs throughout adolescence and adulthood –Sperm are produced continuously without the prolonged interruptions in oogenesis © 2011 Pearson Education, Inc.

63. Epididymis Seminiferous tubule Testis Cross section of seminiferous tubule Sertoli cell nucleus Lumen of seminiferous tubule Plasma membrane Tail Neck Midpiece Head Mitochondria Nucleus Acrosome Primordial germ cell in embryo Mitotic divisions Spermatogonial stem cell Spermatogonium Mitotic divisions Primary spermatocyte Meiosis I Meiosis II Spermatids (two stages) Secondary spermatocyte Early spermatid Sperm cell Differentiation (Sertoli cells provide nutrients) 2n2n 2n2n 2n2n n n n n n n n n nn Figure 46.12a

64. Epididymis Seminiferous tubule Testis Cross section of seminiferous tubule Spermato- gonium Primary spermatocyte Spermatids (two stages) Secondary spermatocyte Sperm cell Sertoli cell nucleus Lumen of seminiferous tubule Figure 46.12aa

65. Primordial germ cell in embryo Mitotic divisions Spermatogonial stem cell Spermatogonium Mitotic divisions Primary spermatocyte Meiosis I Meiosis II Secondary spermatocyte Early spermatid Sperm cell Differentiation (Sertoli cells provide nutrients) 2n2n 2n2n 2n2n n n n n n n n n n n Figure 46.12ab

66. Figure 46.12ac Plasma membrane Tail Neck Midpiece Head Mitochondria Nucleus Acrosome

67. 2n2n 2n2n n n n n Ovary Primordial germ cell Mitotic divisions Oogonium In embryo Primary oocyte (present at birth), arrested in prophase of meiosis I Completion of meiosis I and onset of meiosis II Secondary oocyte, arrested at metaphase of meiosis II First polar body Ovulation, sperm entry Completion of meiosis II Second polar body Primary oocyte within follicle Growing follicle Mature follicle Ruptured follicle Ovulated secondary oocyte Corpus luteum Degenerating corpus luteum Fertilized egg Figure 46.12b

68. Ovary Primary oocyte within follicle Growing follicle Mature follicle Ruptured follicle Ovulated secondary oocyte Corpus luteum Degenerating corpus luteum Figure 46.12ba

69. Figure 46.12bb 2n2n 2n2n n n n n Primordial germ cell Mitotic divisions Oogonium In embryo Primary oocyte (present at birth), arrested in prophase of meiosis I Completion of meiosis I and onset of meiosis II Secondary oocyte, arrested at metaphase of meiosis II First polar body Ovulation, sperm entry Completion of meiosis II Second polar body Fertilized egg

70. Concept 46.4: The interplay of tropic and sex hormones regulates mammalian reproduction Human reproduction is coordinated by hormones from the hypothalamus, anterior pituitary, and gonads Gonadotropin-releasing hormone (GnRH) is secreted by the hypothalamus and directs the release of FSH and LH from the anterior pituitary FSH and LH regulate processes in the gonads and the production of sex hormones © 2011 Pearson Education, Inc.

71. Sex hormones serve many functions in addition to gamete production, including sexual behavior and the development of primary and secondary sex characteristics © 2011 Pearson Education, Inc.

72. Hormonal Control of the Female Reproductive Cycles In females, the secretion of hormones and the reproductive events they regulate are cyclic Prior to ovulation, the endometrium thickens with blood vessels in preparation for embryo implantation If an embryo does not implant in the endometrium, the endometrium is shed in a process called menstruation © 2011 Pearson Education, Inc.

73. Hormones closely link the two cycles of female reproduction –Changes in the uterus define the menstrual cycle (also called the uterine cycle) –Changes in the ovaries define the ovarian cycle © 2011 Pearson Education, Inc.

74. Figure 46.13 Control by hypothalamus(a) Hypothalamus GnRH Anterior pituitary FSHLH Inhibited by combination of estradiol and progesterone Stimulated by high levels of estradiol Inhibited by low levels of estradiol    10987654321 (b)Pituitary gonadotropins in blood LH FSH FSH and LH stimulate follicle to grow 6 LH surge triggers ovulation Ovarian cycle Growing follicle Maturing follicle Corpus luteum Degenerating corpus luteum Follicular phaseOvulationLuteal phase Estradiol secreted by growing follicle in increasing amounts (c) Progesterone and estradiol secreted by corpus luteum (d) Ovarian hormones in blood Estradiol Peak causes LH surge (see ) Progesterone Progesterone and estra- diol promote thickening of endometrium Estradiol level very low (e) Uterine (menstrual) cycle Endometrium Menstrual flow phaseProliferative phase Secretory phase Days 28252015141050

75. Figure 46.13a Control by hypothalamus(a) Hypothalamus GnRH Anterior pituitary FSHLH Inhibited by combination of estradiol and progesterone Stimulated by high levels of estradiol Inhibited by low levels of estradiol    21

76. Figure 46.13b (b)Pituitary gonadotropins in blood LH FSH FSH and LH stimulate follicle to grow LH surge triggers ovulation Ovarian cycle Growing follicle Maturing follicle Corpus luteum Degenerating corpus luteum Follicular phaseOvulationLuteal phase (c) 2825 2015 14 1050 Days 3678

77. Estradiol secreted by growing follicle in increasing amounts Progesterone and estradiol secreted by corpus luteum (d) Ovarian hormones in blood Estradiol Peak causes LH surge (see ) Progesterone Progesterone and estra- diol promote thickening of endometrium Estradiol level very low (e) Uterine (menstrual) cycle Endometrium Menstrual flow phaseProliferative phase Secretory phase Days 28252015141050 4569 (e) Figure 46.13c

78. The Ovarian Cycle The sequential release of GnRH then FSH and LH stimulates follicle growth Follicle growth and an increase in the hormone estradiol characterize the follicular phase of the ovarian cycle The follicular phase ends at ovulation, and the secondary oocyte is released © 2011 Pearson Education, Inc.

79. Animation: Ovulation Right-click slide / select “Play”

80. Following ovulation, the follicular tissue left behind transforms into the corpus luteum; this is the luteal phase The corpus luteum disintegrates, and ovarian steroid hormones decrease © 2011 Pearson Education, Inc.

81. Animation: Post Ovulation Right-click slide / select “Play”

82. The Uterine (Menstrual) Cycle Hormones coordinate the uterine cycle with the ovarian cycle –Thickening of the endometrium during the proliferative phase coordinates with the follicular phase –Secretion of nutrients during the secretory phase coordinates with the luteal phase –Shedding of the endometrium during the menstrual flow phase coordinates with the growth of new ovarian follicles © 2011 Pearson Education, Inc.

83. A new cycle begins if no embryo implants in the endometrium Cells of the uterine lining can sometimes migrate to an abnormal, or ectopic, location Swelling of these cells in response to hormone stimulation results in a disorder called endometriosis © 2011 Pearson Education, Inc.

84. Menopause After about 500 cycles, human females undergo menopause, the cessation of ovulation and menstruation Menopause is very unusual among animals Menopause might have evolved to allow a mother to provide better care for her children and grandchildren © 2011 Pearson Education, Inc.

85. Menstrual Versus Estrous Cycles Menstrual cycles are characteristic only of humans and some other primates –The endometrium is shed from the uterus in a bleeding called menstruation –Sexual receptivity is not limited to a time frame © 2011 Pearson Education, Inc.

86. Estrous cycles are characteristic of most mammals –The endometrium is reabsorbed by the uterus –Sexual receptivity is limited to a “heat” period –The length and frequency of estrus cycles vary from species to species © 2011 Pearson Education, Inc.

87. FSH promotes the activity of Sertoli cells, which nourish developing sperm LH regulates Leydig cells, which secrete testosterone and other androgens, which in turn promote spermatogenesis © 2011 Pearson Education, Inc. Hormonal Control of the Male Reproductive System

88. © 2011 Pearson Education, Inc. Animation: Male Hormones Right-click slide / select “Play”

89. Hypothalamus    GnRH Anterior pituitary FSHLH Sertoli cells Leydig cells InhibinSpermatogenesisTestosterone Testis Negative feedback Figure 46.14

90. Testosterone regulates the production of GnRH, FSH, and LH through negative feedback mechanisms Sertoli cells secrete the hormone inhibin, which reduces FSH secretion from the anterior pituitary © 2011 Pearson Education, Inc.

91. Two reactions predominate in both sexes –Vasocongestion, the filling of tissue with blood –Myotonia, increased muscle tension The sexual response cycle has four phases: excitement, plateau, orgasm, and resolution Excitement prepares the penis and vagina for coitus (sexual intercourse) © 2011 Pearson Education, Inc. Human Sexual Response

92. Direct stimulation of genitalia maintains the plateau phase and prepares the vagina for receipt of sperm Orgasm is characterized by rhythmic contractions of reproductive structures –In males, semen is first released into the urethra and then ejaculated from the urethra –In females, the uterus and outer vagina contract © 2011 Pearson Education, Inc.

93. During the resolution phase, organs return to their normal state and muscles relax © 2011 Pearson Education, Inc.

94. Concept 46.5: In placental mammals, an embryo develops fully within the mother’s uterus An egg develops into an embryo in a series of predictable events © 2011 Pearson Education, Inc.

95. Conception, Embryonic Development, and Birth Conception, fertilization of an egg by a sperm, occurs in the oviduct The resulting zygote begins to divide by mitosis in a process called cleavage Division of cells gives rise to a blastocyst, a ball of cells with a central cavity © 2011 Pearson Education, Inc.

96. 54123 Cleavage Fertilization Ovary Ovulation Uterus Cleavage continues Implantation Endometrium (a) From ovulation to implantation (b) Implantation of blastocyst Endometrium Cavity Inner cell mass Blastocyst Trophoblast Figure 46.15

97. After blastocyst formation, the embryo implants into the endometrium The embryo releases human chorionic gonadotropin (hCG), which prevents menstruation Pregnancy, or gestation, is the condition of carrying one or more embryos in the uterus Duration of pregnancy in other species correlates with body size and maturity of the young at birth © 2011 Pearson Education, Inc.

98. Pregnancies can terminate spontaneously due to chromosomal or developmental abnormalities An ectopic pregnancy occurs when a fertilized egg begins to develop in the fallopian tube © 2011 Pearson Education, Inc.

99. First Trimester Human gestation can be divided into three trimesters of about three months each The first trimester is the time of most radical change for both the mother and the embryo During implantation, the endometrium grows over the blastocyst © 2011 Pearson Education, Inc.

100. During its first 2 to 4 weeks, the embryo obtains nutrients directly from the endometrium Meanwhile, the outer layer of the blastocyst, called the trophoblast, mingles with the endometrium and eventually forms the placenta Blood from the embryo travels to the placenta through arteries of the umbilical cord and returns via the umbilical vein © 2011 Pearson Education, Inc.

101. Figure 46.16 Placenta Uterus Umbilical cord Chorionic villus, containing fetal capillaries Maternal blood pool Maternal arteries Maternal veins Maternal portion of placenta Fetal portion of placenta (chorion) Umbilical arteries Umbilical vein Umbilical cord Fetal venuleFetal arteriole

102. Splitting of the embryo during the first month of development results in genetically identical twins Release and fertilization of two eggs result in fraternal and genetically distinct twins © 2011 Pearson Education, Inc.

103. The first trimester is the main period of organogenesis, development of the body organs All the major structures are present by 8 weeks, and the embryo is called a fetus © 2011 Pearson Education, Inc.

104. Changes occur in the mother –Mucus plug to protect against infection –Growth of the placenta and uterus –Cessation of ovulation and the menstrual cycle –Breast enlargement –Nausea is also very common © 2011 Pearson Education, Inc.

105. Figure 46.17 (a) 5 weeks (b) 14 weeks (c) 20 weeks

106. Figure 46.17a (a) 5 weeks

107. Figure 46.17b (b) 14 weeks

108. Figure 46.17c (c) 20 weeks

109. Second Trimester During the second trimester –The fetus grows and is very active –The mother may feel fetal movements –The uterus grows enough for the pregnancy to become obvious © 2011 Pearson Education, Inc.

110. Third Trimester During the third trimester, the fetus grows and fills the space within the embryonic membranes A complex interplay of local regulators and hormones induces and regulates labor, the process by which childbirth occurs © 2011 Pearson Education, Inc.

111. Figure 46.18 Estradiol   from ovaries Activates oxytocin receptors on uterus Oxytocin from fetus and mother’s posterior pituitary Prostaglandins Positive feedback Stimulates uterus to contract Stimulates placenta to make Stimulate more contractions of uterus

112. Labor typically has three stages –Thinning and opening of the cervix, or dilation –Expulsion or delivery of the baby –Delivery of the placenta © 2011 Pearson Education, Inc.

113. Figure 46.19 Dilation of the cervix 213 Placenta Umbilical cord Uterus Cervix Expulsion: delivery of the infant Delivery of the placenta Uterus Umbilical cord Placenta (detaching)

114. Figure 46.19a Dilation of the cervix 1 Placenta Umbilical cord Uterus Cervix

115. Figure 46.19b Expulsion: delivery of the infant 2

116. Figure 46.19c Delivery of the placenta Uterus Umbilical cord Placenta (detaching) 3

117. Delivery of the baby and placenta is brought about by a series of strong, rhythmic uterine contractions Lactation, the production of milk, is unique to mammals © 2011 Pearson Education, Inc.

118. Maternal Immune Tolerance of the Embryo and Fetus A woman’s acceptance of her “foreign” offspring is not fully understood It may be due to suppression of the immune response in her uterus © 2011 Pearson Education, Inc.

119. Contraception and Abortion Contraception, the deliberate prevention of pregnancy, can be achieved in a number of ways Contraceptive methods fall into three categories –Preventing release of eggs and sperm –Keeping sperm and egg apart –Preventing implantation of an embryo © 2011 Pearson Education, Inc.

120. A health-care provider should be consulted for complete information on the choice and risks of contraception methods © 2011 Pearson Education, Inc.

121. Figure 46.20 Male Female Method Event Vasectomy Abstinence Condom Coitus interruptus (very high failure rate) Production of sperm Production of primary oocytes Sperm transport down male duct system Oocyte development and ovulation Combination birth control pill (or injection, patch, or vaginal ring) Abstinence Female condom Sperm deposited in vagina Capture of the oocyte by the oviduct Sperm movement through female reproductive tract Transport of oocyte in oviduct Tubal ligation Spermicides; diaphragm; progestin alone (as minipill or injection) Meeting of sperm and oocyte in oviduct Union of sperm and egg Implantation of blastocyst in endometrium Morning-after pill; intrauterine device (IUD)

122. Male Female Method Event Vasectomy Abstinence Condom Coitus interruptus (very high failure rate) Production of sperm Production of primary oocytes Sperm transport down male duct system Oocyte development and ovulation Combination birth control pill (or injection, patch, or vaginal ring) Abstinence Female condom Sperm deposited in vagina Capture of the oocyte by the oviduct Tubal ligation Spermicides; diaphragm; progestin alone (as minipill or injection) Figure 46.20a

123. Figure 46.20b Sperm movement through female reproductive tract Transport of oocyte in oviduct Meeting of sperm and oocyte in oviduct Union of sperm and egg Implantation of blastocyst in endometrium Morning-after pill; intrauterine device (IUD) Male Female Method Event

124. The rhythm method, or natural family planning, is to refrain from intercourse when conception is most likely; it has a pregnancy rate of 10–20% Coitus interruptus, the withdrawal of the penis before ejaculation, is unreliable Barrier methods block fertilization with a pregnancy rate of less than 10% –A condom fits over the penis –A diaphragm is inserted into the vagina before intercourse © 2011 Pearson Education, Inc.

125. Intrauterine devices (IUDs) are inserted into the uterus and interfere with fertilization and implantation; the pregnancy rate is less than 1% Female birth control pills are hormonal contraceptives with a pregnancy rate of less than 1% © 2011 Pearson Education, Inc.

126. Sterilization is permanent and prevents the release of gametes –Tubal ligation ties off the oviducts –Vasectomy ties off the vas deferens Abortion is the termination of a pregnancy Spontaneous abortion, or miscarriage, occurs in up to one-third of all pregnancies The drug RU486 results in an abortion within the first 7 weeks of a pregnancy © 2011 Pearson Education, Inc.

127. Modern Reproductive Technologies Recent advances are addressing reproductive problems © 2011 Pearson Education, Inc.

128. Detecting Disorders During Pregnancy Amniocentesis and chorionic villus sampling are invasive techniques in which amniotic fluid or fetal cells are obtained for genetic analysis Noninvasive procedures usually use ultrasound imaging to detect fetal condition Genetic testing of the fetus poses ethical questions and can present parents with difficult decisions © 2011 Pearson Education, Inc.

129. Treating Infertility Modern technology can provide infertile couples with assisted reproductive technologies In vitro fertilization (IVF) mixes eggs with sperm in culture dishes and returns the embryo to the uterus at the 8-cell stage Sperm are injected directly into an egg in a type of IVF called intracytoplasmic sperm injection (ICSI) © 2011 Pearson Education, Inc.

130. Video: Ultrasound of Human Fetus 1

131. © 2011 Pearson Education, Inc. Video: Ultrasound of Human Fetus 2

132. Human gametogenesis Spermatogenesis Oogenesis Primary spermatocyte Primary oocyte Secondary spermatocytes Secondary oocyte Polar body Spermatids Sperm Polar body Fertilized egg 2n2n 2n2n n n n n n n nnnn nnnn Figure 46.UN01

133. Figure 46.UN02