Chapter 46 Animal Reproduction

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

Figure 46.3 Sexual behavior in parthenogenetic lizards Time Ovary size Hormones Behavior Ovulation Progesterone Estrogen Female- like Male- like (a) Both lizards in this photograph are C. uniparens females. The one on top is playing the role of a male. Every two or three weeks during the breeding season, individuals switch sex roles. (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.

Figure 46.1 Earthworms mating

Figure 46.5 External fertilization Eggs

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

Vagina Uterus Cervix Ovaries Oviduct Uterine wall Endometrium Follicles Corpus luteum

Figure 46.13b Oogenesis

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

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

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

Activity 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

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

Figure 46.12 Structure of a human sperm cell

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

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

Activity 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?”

Figure 46.14 Hormonal control of the testes Stimuli from other areas in the brain Hypothalamus GnRH from the hypothalamus reg- ulates FSH and LH release from the anterior pituitary. 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. Anterior pituitary Negative feedback Leydig cells make testosterone Primary and secondary sex characteristics Sertoli cells Spermatogenesis Testis

From ovulation to implantation Implantation of blastocyst Figure 46.15 Formation of the zygote and early postfertilization events Ovary Uterus Endometrium From ovulation to implantation Inner cell mass Cavity Blastocyst Trophoblast Ovulation releases a secondary oocyte, which enters the oviduct. 1 The blastocyst implants in the endometrium about 7 days after conception. 5 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. 4 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 Cleavage (cell division) begins in the oviduct as the embryo is moved toward the uterus by peristalsis and the movements of cilia. 3 (a) Implantation of blastocyst (b)

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

Figure 46.17 Human fetal development 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. (a) 14 weeks. Growth and development of the offspring, now called a fetus, continue during the second trimester. This fetus is about 6 cm long. (b) 20 weeks. By the end of the second trimester (at 24 weeks), the fetus grows to about 30 cm in length. (c)

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

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

Figure 46.20 Mechanisms of some contraceptive methods Male Female Method Event Production of viable sperm viable oocytes Vasectomy Combination birth control pill (or injection, patch, or vaginal ring) Sperm transport down male duct system Ovulation 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) movement through female reproductive tract Transport of oocyte in Meeting of sperm and oocyte in oviduct Morning-after pill (MAP) Union of sperm and egg Implantation of blastocyst in properly prepared endometrium Birth Progestin alone

Figure 46.21 Ultrasound image Head Body

46.21 Ultrasound Of Fetus 1

46.21 Ultrasound Of Fetus 2