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Chapter 46

Chapter 46. Animal Reproduction. Figure 46.2 Asexual reproduction of a sea anemone ( Anthopleura elegantissima ).

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Chapter 46

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  1. Chapter 46 Animal Reproduction

  2. Figure 46.2 Asexual reproduction of a sea anemone (Anthopleura elegantissima)

  3. (a) Both lizards in this photograph are C.uniparensfemales. The one on top is playing the role of a male. Every two or three weeks during the breeding season, individuals switch sex roles. Ovarysize Ovulation Ovulation Progesterone Estrogen Hormones (b) The sexual behavior of C. uniparens is correlated with the cycle of ovulation mediated by sex hormones. As blood levels of estrogen rise, the ovaries grow, and the lizard behaves like a female. After ovulation, the estrogen level drops abruptly, and the progesterone level rises; these hormone levels correlate with male behavior. Time Behavior Female-like Male-like Female-like Male-like Figure 46.3 Sexual behavior in parthenogenetic lizards

  4. Figure 46.1 Earthworms mating

  5. Eggs Figure 46.5 External fertilization

  6. Uterus (Urinary bladder) Oviduct (Pubic bone) Ovary (Rectum) Cervix Vagina Urethra Shaft Prepuce Clitoris Bartholin’s gland Glans Labia minora Vaginal opening Labia majora Figure 46.9 Reproductive anatomy of the human female

  7. Oviduct Ovaries Follicles Uterine wall Uterus Cervix Endometrium Corpus luteum Vagina

  8. Figure 46.13b Oogenesis

  9. Figure 46.9x Ovary (left) and follicle (right)

  10. (Urinarybladder) Seminal vesicle (behind bladder) Prostate gland Bulbourethral gland Urethra Erectile tissue of penis Scrotum Vas deferens Epididymis Glans penis Testis Figure 46.10 Reproductive anatomy of the human male

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

  12. Work in groups to tell me about the travel of a group of sperm to see the legendary follicle Each member of your group will need to choose a role from below: Leader, Reporter, Recorder, Noise monitor Start out in the seminiferous tubules and work your way to the follicle Be sure to include structure and function This is a G rated classroom Activity

  13. Epididymis Seminiferous tubule Testis Cross section of seminiferous tubule 2n Spermatogonium Sertoli cell nucleus Mitotic division, producing large numbers of spermatogonia Differentiation and Onset of meiosis I Primary spermatocyte (in prophase of meiosis I) 2n Meiosis I completed n n Secondary spermatocyte Meiosis II Lumen of Seminiferous tubule Spermatids (at two stages of differentiation) Early spermatids n n n n Differentiation (Sertoli cells provide nutrients) Sperm cells n n Neck n n Head Midpiece Tail Plasma membrane Mitochondria Nucleus Acrosome Figure 46.12 Human Spermatogenesis

  14. Figure 46.12 Structure of a human sperm cell

  15. Ovary Primary germ cell in embryo Differentiation Oogonium in ovary Oogonium 2n Mitotic division Primary oocyte within follicle Primary oocyte, arrested in prophase of meiosis I (present at birth) 2n Growing follicle Completion of meiosis I and onset of meiosis II First polar body n Secondary oocyte, arrested at meta- phase of meiosis II n Ovulation Mature follicle Entry of sperm triggers completion of meiosis II n n Ruptured follicle Ovum Ovulated secondary oocyte Corpus luteum Degenerating corpus luteum Figure 46.11 Human Oogenesis Second polar body

  16. Figure 46.13 The reproductive cycle of the human female Control by hypothalamus (a) Inhibited by combination of estrogen and progesterone Hypothalamus Stimulated by high levels of estrogen GnRH 1 Inhibited by low levels of estrogen Anterior pituitary LH FSH 2 (b) Pituitary gonadotropins in blood 6 LH FSH FSH and LH stimulate follicle to grow LH surge triggers ovulation 3 (c) Ovarian cycle 7 8 Corpus luteum Degenerating corpus luteum Growing follicle Mature follicle Ovulation Luteal phase Follicular phase Progesterone and estrogen secreted by corpus luteum Estrogen secreted by growing follicle in increasing amounts 4 Peak causes LH surge Ovarian hormones in blood (d) 5 10 Progesterone Estrogen 9 Progesterone and estro- gen promote thickening of endometrium Estrogen level very low (e) Uterine (menstrual) cycle • Endometrium Secretory phase Menstrual flow phase Proliferative phase 25 28 5 14 15 0 20 10 Days

  17. Work in pairs to compare the timing of the menstrual and ovarian cycles Answer: “Why does it make sense that each phase occurs when it does?” Activity

  18. Stimuli from other areas in the brain Hypothalamus GnRH from the hypothalamus reg- ulates FSH and LH release from the anterior pituitary. Anterior pituitary Negative feedback FSH acts on the Sertoli cells of the seminiferous tubules, promoting spermatogenesis. LH stimulates the Leydig cells to make testosterone, which in turn stimulates sperm production. Leydig cells make testosterone Primary and secondary sex characteristics Sertoli cells Spermatogenesis Testis Figure 46.14 Hormonal control of the testes

  19. Cleavage (cell division) begins in the oviduct as the embryo is moved toward the uterus by peristalsis and the movements of cilia. Cleavage continues. By the time the embryo reaches the uterus, it is a ball of cells. It floats in the uterus for several days, nourished by endometrial secretions. It becomes a blastocyst. 3 4 Ovary Fertilization occurs. A sperm enters the oocyte; meiosis of the oocyte finishes; and the nuclei of the ovum and sperm fuse, producing a zygote. 2 The blastocyst implants in the endometrium about 7 days after conception. 5 Uterus Ovulation releases a secondary oocyte, which enters the oviduct. 1 Endometrium (a) From ovulation to implantation Endometrium Inner cell mass Cavity Trophoblast Blastocyst (b) Implantation of blastocyst Figure 46.15 Formation of the zygote and early postfertilization events

  20. Maternal veins Maternal arteries Placenta Maternal portion of placenta Umbilical cord Chorionic villus containing fetal capillaries Fetal portion of placenta (chorion) Maternal blood pools Uterus Umbilical arteries Fetal arteriole Umbilical vein Fetal venule Umbilical cord Figure 46.16 Placental circulation

  21. (c) (b) (a) 20 weeks. By the end of the second trimester (at 24 weeks), the fetus grows to about 30 cm in length. 5 weeks. Limb buds, eyes, the heart, the liver, and rudiments of all other organs have started to develop in the embryo, which is only about 1 cm long. 14 weeks. Growth and development of the offspring, now called a fetus, continue during the second trimester. This fetus is about 6 cm long. Figure 46.17 Human fetal development

  22. Estrogen Oxytocin from fetus and mother's posterior pituitary from ovaries Positive feedback Induces oxytocin receptors on uterus Stimulates uterus to contract Stimulates placenta to make Prostaglandins Stimulate more contractions of uterus Figure 46.18 A model for the induction of labor

  23. Placenta Umbilical cord Uterus Cervix 1 Dilation of the cervix 2 Expulsion: delivery of the infant Uterus Placenta (detaching) Umbilical cord 3 Delivery of the placenta Figure 46.19 The three stages of labor

  24. Female Male Event Event Method Method Production of viable sperm Production of viable oocytes Vasectomy Combination birth control pill (or injection, patch, or vaginal ring) Sperm transport down male duct system Ovulation Abstinence Abstinence Condom Coitus interruptus (very high failure rate) Sperm deposited in vagina Capture of the oocyte by the oviduct Tubal ligation Spermicides; diaphragm; cervical cap; progestin alone (minipill, implant, or injection) Sperm movement through female reproductive tract Transport of oocyte in oviduct Meeting of sperm and oocyte in oviduct Morning-after pill (MAP) Union of sperm and egg Progestin alone Implantation of blastocyst in properly prepared endometrium Birth Figure 46.20 Mechanisms of some contraceptive methods

  25. Head Body Head Body Figure 46.21 Ultrasound image

  26. 46.21 Ultrasound Of Fetus 1

  27. 46.21 Ultrasound Of Fetus 2

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