Both asexual and sexual reproduction occur in the animal kingdom

1. Both asexual and sexual reproductionoccur in the animal kingdom • Asexual reproduction is creation of offspring whose genes all come from one parent • Sexual reproduction is creation of offspring by fusion of male gametes (sperm) and female gametes (eggs) to form zygotes

2. In budding, two new individuals arise from outgrowths of existing ones • Fragmentation is breaking of the body into pieces, some or all of which develop into adults

3. Parthenogenesis is a process in which an egg develops without being fertilized • Several genera of fishes, amphibians, and lizards reproduce only by a complex form of parthenogenesis

4. Ovary size Ovulation Ovulation Estrogen Progesterone Hormone level Time Behavior Female- like Male- like Female- like Male- like

5. Sexual reproduction is a special problem for organisms that seldom encounter a mate • One solution is hermaphroditism, in which each individual has male and female reproductive systems • In sequential hermaphroditism, an individual reverses its sex during its lifetime

6. Fertilization depends on mechanisms that help sperm meet 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

7. Mating animals may use pheromones, chemical signals released by one organism that influence the behavior or physiology of other individuals of the same species. • Pheromones are small, volatile, or water-soluble molecules that disperse into the environment. • Like hormones, pheromones are active in minute amounts. • Many pheromones act as male attractants.

8. The female reproductive system includes a spermatheca, a sac in which sperm may be stored for a year or more. Accessory gland Ovary Ejaculatory duct Testis Oviduct Spermatheca Penis Vas deferens Vagina Seminal vesicle Accessory gland Male honeybee (drone) Female honeybee (queen)

9. In many nonmammalian vertebrates, the digestive, excretory, and reproductive systems share a common opening to the outside, the cloaca. • Mammals have separate openings for the digestive and reproductive systems. • Female mammals also have separate openings for the excretory and reproductive systems. • The uterus of most vertebrates is partly or completely divided into two chambers.

10. Male reproductive systems differ mainly in copulatory organs. • Many mammalian vertebrates do not have a well-developed penis and simply turn the cloaca inside out to ejaculate.

11. 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

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

13. Ovaries • The female gonads, the ovaries, lie in the abdominal cavity • Each ovary is enclosed in a tough protective capsule and contains many follicles • A follicle consists of one egg surrounded by one or more layers of follicle cells

14. Ovulation expels an egg cell from the follicle • The remaining follicular tissue grows within the ovary, forming a mass called the corpus luteum • The corpus luteum secretes hormones, depending on whether pregnancy occurs

15. Oviducts and Uterus • The egg cell is released into the abdominal cavity near the opening of the oviduct or fallopian tube • Cilia in the tube convey the egg to the uterus • Cervix is the neck of the uterus. • The vagina is a thin-walled chamber that is the repository for sperm during copulation and serves as the birth canal

16. Male Reproductive Anatomy • In most mammals, the male’s external reproductive organs are the scrotum and penis • Internal organs are the gonads, which produce sperm and hormones, and accessory glands

17. Seminal vesicle (behind bladder) (Urinary bladder) Prostate gland Bulbourethral gland Urethra Erectile tissue of penis Scrotum Vas deferens Epididymis Glans penis Testis

18. Testes • The male gonads, or testes, consist of highly coiled tubes surrounded by connective tissue • Sperm form in these seminiferous tubules • Production of normal sperm cannot occur at the body temperatures of most mammals • The testes of many mammals are held outside the abdominal cavity in the scrotum, where the temperature is lower than in the abdominal cavity

19. 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

20. Glands • Three sets of accessory glands add secretions to the semen, the fluid that is ejaculated • The two seminal vesicles contribute about 60% of the total volume of semen

21. Once in the female reproductive tract, prostaglandins in semen thin the mucus at the opening of the uterus and stimulate uterine contractions that help move the semen. • When ejaculated, semen coagulates, making it easier for uterine contractions to move it along. • Anticoagulants then liquefy the semen, and the sperm begin swimming. • The alkalinity of semen helps neutralize the acidic environment of the vagina, protecting the sperm and increasing their motility.

22. The prostate gland secretes its products directly into the urethra through several small ducts • The bulbourethral gland secretes a clear mucus before ejaculation that neutralizes acidic urine remaining in the urethra

23. In humans and other mammals, a complex interplay of hormones regulates gametogenesis • The process of gametogenesis is based on meiosis, but differs in females and males • Oogenesis is development of mature ova • Spermatogenesis is production of mature sperm

24. Ovary Primary germ cell in embryo Differentiation Oogonium in ovary Oogonium Mitotic division Primary oocyte within follicle Primary oocyte Completion of meiosis I and onset of meiosis II Growing follicle Secondary oocyte First polar body Ovulation Mature follicle Entry of sperm triggers completion of meiosis II Ruptured follicle Second polar body Ovum Ovulated secondary oocyte Corpus luteum Degen- erating corpus luteum

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

26. Menstrual Versus Estrous Cycles • Two different types of cycles occur in females • Humans and other primates have menstrual cycles; other mammals have estrous cycles • In both cases, ovulation occurs after the endometrium has started to thicken in preparation for implantation

27. In menstrual cycles: • The endometrium is shed from the uterus in a bleeding called menstruation • Sexual receptivity is not limited to a timeframe • In estrous cycles: • The endometrium is reabsorbed by the uterus • Sexual receptivity is limited to a “heat” period

28. The Human Female Reproductive Cycle: A Closer Look • The female reproductive cycle is one integrated cycle involving two organs: the uterus and ovaries • Secretion of GnRH from the hypothalamus and of FSH and LH from the anterior pituitary orchestrates the female reproductive cycle • Five kinds of hormones participate in an elaborate scheme involving positive and negative feedback

29. Control by hypothalamus Inhibited by combination of estrogen and progesterone Hypothalamus Stimulated by high levels of estrogen GnRH Anterior pituitary Inhibited by low levels of estrogen FSH LH Pituitary gonadotropins in blood LH FSH FSH and LH stimulate follicle to grow LH surge triggers ovulation Ovarian cycle Degenerating corpus luteum Corpus luteum Growing follicle Mature follicle Follicular phase Ovulation Luteal phase Estrogen secreted by growing follicle in increasing amounts Progesterone and estrogen secreted by corpus luteum Ovarian hormones in blood Peak causes LH surge Progesterone Estrogen Estrogen level very low Progesterone and estro- gen promote thickening of endometrium Uterine (menstrual) cycle Endometrium Menstrual flow phase Proliferative phase Secretory phase Days 0 5 10 20 25 14 15 28

30. The Ovarian Cycle • In the ovarian cycle, hormones stimulate follicle growth, which results in ovulation • Following ovulation, the follicular tissue left behind transforms into the corpus luteum

31. The Uterine (Menstrual) Cycle • Cycle after cycle, the maturation and release of egg cells from the ovary are integrated with changes in the uterus • If an embryo has not implanted in the endometrium by the end of the secretory phase, a new menstrual flow commences

32. Conception, Embryonic Development, and Birth • Conception, fertilization of an egg by a sperm, occurs in the oviduct • After fertilization, the zygote undergoes cleavage and develops into a blastocyst before implantation in the endometrium

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

34. Estrogen Oxytocin from ovaries from fetus and mother’s posterior pituitary Induces oxytocin receptors on uterus Positive feedback Stimulates uterus to contract Stimulates placenta to make Prostaglandins Stimulate more contractions of uterus

35. Animations and Videos • Bozeman - The Reproductive System • The Reproductive Years • Pituitary and Ovarian Hormones Control the Ovarian Cycle • Ovarian Hormones Control the Uterine Cycle • Events of the Ovarian and Uterine Cycles • Maturation of the Follicle and Oocyte • Chapter Quiz Questions – 1 • Chapter Quiz Questions – 2