Chapter 16: Human Reproduction

Identify the organs of the male and female reproductive systems. Label a diagram

Seminal vesicle (Rectum) Vas deferens Ejaculatory duct Prostate gland Bulbourethral gland (Urinary bladder) (Pubic bone) Erectile tissue of penis Urethra Glans penis Prepuce Vas deferens Epididymis Testis Scrotum External – scrotum & penis Internal – gonads produce sperm & hormones - testes – packed with highly coiled seminiferous tubules - accessory glands that help sperm move: - seminal vesicles - bulbourethral glands - prostate gland male reproductive tract:

Erectile tissue of penis Prostate gland (Urinary bladder) Bulbourethral gland Vas deferens Epididymis Testis Seminal vesicle (behind bladder) Urethra Scrotum Glans penis sperm pathway during ejaculation: epididymis  vas deferens  ejaculatory duct sperm count during ejaculation: 2 – 5 mL of semen per ejaculation x 50 – 130 million sperm per mL 100 – 650 million sperm per ejaculation

female reproductive anatomy Glans (Rectum) Cervix Vagin a Bartholin’s gland Vaginal opening Ovary Oviduct Labia majora Labia minora (Urinary bladder) (Pubic bone) Uterus Urethra Shaft Prepuce Clitoris External – clitoris & 2 sets of labia which surround the clitoris & vaginal opening Internal – pair of gonads (ovaries) with ducts & chambers for gametes & fetus

Vagina Uterus Cervix Ovaries Oviduct Uterine wall Endometrium Follicles Corpus luteum Ovaries – contain many follicles Follicle – formed before birth - egg cell surrounded by follicle cells - nourish & protect the egg - produce estrogens - Endometrium – inner lining of uterus - After ovulation, “egg” falls down the oviduct into uterus

Table meetings 1.What are the endocrine and exocrine products of the testes? 2.What is the composition of semen and the glands that produce it? 3.Trace the pathway followed by a sperm from the testis to the body exterior. 4.Describe the functions of the vesicular follicle and corpus luteum of the ovary. 5.Describe endometrium, myometrium and ovulation. 6.Trace the pathway an egg takes from ovary to the body exterior.

Table meetings 1.What are the endocrine and exocrine products of the testes? 1.Endocrine products – testosterone 2.Exocrine products – sperm and semen

Table meetings 2. What is the composition of semen and the glands that produce it? Fructose from seminal vesicles Prostate gland releases milky fluid Bulbourethral glands releases clear mucus 3. Trace the pathway followed by a sperm from the testis to the body exterior. Testis  epididymis  vas deferens  urethra  out

4. Describe the functions of the vesicular follicle and corpus luteum of the ovary. Vesicular follicle – develops the egg in an ovary Corpus luteum – follicle left after egg is released, develops the lining of the uterus for fertilized egg 5. Describe endometrium, myometrium and ovulation. Endometrium – lining of the uterus Myometrium – middle layer of uterus, muscular Ovulation – release of an egg from an ovary.

6. Trace the pathway an egg takes from ovary to the body exterior. Ovary  fallopian tube  uterus  cervix  vagina  out

Chapter 16: Animal Reproduction 2 ways animals reproduce: -Asexual – mitosis – same genes as parent -Fission – separation of a parent into 2 -Budding – individuals split as an outgrowth from an existing one -Some cnidarians -Fragmentation – breaking of the body into several pieces followed by regeneration -Sponges, cnidarians, tunicates -Sexual – fusion of haploid gametes -Motile sperm swims to non-motile egg -Increases genetic variability

2 types of sexual reproduction: 1.External – eggs shed by female & fertilized by male in wet environment -Courtship behaviors involved -Pheromones used 2. Internal - sperm deposited in or near female reproductive tract & fertilized within female -Fewer zygotes but more parental care -Embryo develops in reproductive tract

Figure 46.5 External fertilization Eggs

Parthenogenesis: -Process - an egg develops w/o fertilization -Produces haploid adults who produce eggs without meiosis -Daphnia (water flea), bees (male drones), wasps, ants

Figure 46.3 Sexual behavior in parthenogenetic lizards Time Ovary size Hormones Behavior Ovulation Progesterone Estrogen Female- like Male- like 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.

after ejaculation: Prostaglandins in semen thin mucus at the uterus opening, stimulates uterine contractions helps semen move up uterus Semen (slightly alkaline) neutralizes vagina (slightly acidic) -Protects sperm/increases motility -Initially sperm - coagulated -become liquefied so can swim

Viagra: -Promotes action of nitric oxide (NO) -enhances relaxation of smooth muscle in blood vessels of penis so blood can enter erectile tissue

Formation of “eggs”: - 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 follicle Mature follicle Ruptured follicle Ovulated secondary oocyte Corpus luteum Degenerating corpus luteum 2n2n 2n2n n n n n Second polar body Follicles grow in response to FSH completing meiosis I & stopping at metaphase II Smaller polar body is discarded Secondary oocyte is ovulated…NOT AN EGG Meiosis is completed IF 2 nd oocyte is fertilized After ovulation, remaining tissue reorganizes to form the corpus luteum

Epididymis Seminiferous tubule Testis Cross section of seminiferous tubule Sertoli cell nucleus Lumen of Seminiferous tubule 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 HeadMidpiece 2n2n 2n2n n n n nnn n n n n Differentiation and Onset of meiosis I Formation of sperm - Spermatogenesis Seminiferous tubules – produce sperm Leydig cells – secrete testosterone/other androgens Sertoli cells – provide nutrition for spermatids so they can mature - Takes 65 – 75 days to make sperm - 20 days to travel to epididymis -mature & are stored

differences b/t spermatogenesis & oogenesis: Unequal cytokinesis in oogenesis produces 1 haploid ovum (& 2 polar bodies) Equal cytokinesis - 4 haploid sperm Spermatogenesis meiosis occurs throughout males life post puberty, ovary has all its follicles at birth Oogenesis - long resting periods spermatogenesis is uninterrupted & continuous

hormonal control of the menstrual cycle:

Figure The reproductive cycle of the human female Control by hypothalamus Inhibited by combination of estrogen and progesterone Stimulated by high levels of estrogen Inhibited by low levels of estrogen Hypothalamus Anterior pituitary GnRH FSH LH Pituitary gonadotropins in blood LH FSH FSH and LH stimulate follicle to grow LH surge triggers ovulation Ovarian cycle Growing follicle Mature follicle Corpus luteum Degenerating corpus luteum Estrogen secreted by growing follicle in increasing amounts Progesterone and estrogen secreted by corpus luteum Follicular phase Luteal phaseOvulation Ovarian hormones in blood Peak causes LH surge Estrogen Progesterone Estrogen level very low Progesterone and estro- gen promote thickening of endometrium Uterine (menstrual) cycle Endometrium Menstrual flow phase Proliferative phase Secretory phase Days 1 (a) (b) (c) (d) (e) GnRH – Gonadotropin Releasing Hormone -hypothalamus stimulates release of FSH & LH by anterior pituitary

Figure The reproductive cycle of the human female Control by hypothalamus Inhibited by combination of estrogen and progesterone Stimulated by high levels of estrogen Inhibited by low levels of estrogen Hypothalamus Anterior pituitary GnRH FSH LH Pituitary gonadotropins in blood LH FSH FSH and LH stimulate follicle to grow LH surge triggers ovulation Ovarian cycle Growing follicle Mature follicle Corpus luteum Degenerating corpus luteum Estrogen secreted by growing follicle in increasing amounts Progesterone and estrogen secreted by corpus luteum Follicular phase Luteal phaseOvulation Ovarian hormones in blood Peak causes LH surge Estrogen Progesterone Estrogen level very low Progesterone and estro- gen promote thickening of endometrium Uterine (menstrual) cycle Endometrium Menstrual flow phase Proliferative phase Secretory phase Days 1 (a) (b) (c) (d) (e) FSH- Follicle Stimulating Hormone - follicle grows & expresses LH receptors LH- Lutenizing Hormone - triggers ovulation (1 day after LH peak) - stimulates formation of corpus luteum Estrogen – produced by growing follicle - stimulates GnRH release which triggers more LH & FSH - estrogen peak causes LH peak Progesterone – from corpus luteum - maintains thick endometrium in preparation for embryo implant

Figure The reproductive cycle of the human female Control by hypothalamus Inhibited by combination of estrogen and progesterone Stimulated by high levels of estrogen Inhibited by low levels of estrogen Hypothalamus Anterior pituitary GnRH FSH LH Pituitary gonadotropins in blood LH FSH FSH and LH stimulate follicle to grow LH surge triggers ovulation Ovarian cycle Growing follicle Mature follicle Corpus luteum Degenerating corpus luteum Estrogen secreted by growing follicle in increasing amounts Progesterone and estrogen secreted by corpus luteum Follicular phase Luteal phaseOvulation Ovarian hormones in blood Peak causes LH surge Estrogen Progesterone Estrogen level very low Progesterone and estro- gen promote thickening of endometrium Uterine (menstrual) cycle Endometrium Menstrual flow phase Proliferative phase Secretory phase Days 1 (a) (b) (c) (d) (e) If pregnancy does not occur the endometrium is shed….menstruation. Menopause – cessation of ovulation & menstruation because ovaries lose responsiveness to LH & FSH & estrogen decreases

hormonal control of male reproductive system: - GnRH, FSH, & LH

Figure 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

pregnancy tests: -HCG – human chorionic gonadotropin -Mimics LH which keeps corpus luteum secreting estrogen & progesterone -Endometrium stays thick

Events after fertilization.

Fig Formation of the zygote and early post-fertilization events Ovary Uterus Endometrium From ovulation to implantation Endometrium 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) Inner cell mass – develops into embryo & extra-embryonic membranes

Fig Formation of the zygote and early post-fertilization events Ovary Uterus Endometrium From ovulation to implantation Endometrium 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) Trophoblast – outer layer of blastocyst that grows out & mingles with endometrium & helps form the placenta

Fig Formation of the zygote and early post-fertilization events Ovary Uterus Endometrium From ovulation to implantation Endometrium 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) Placenta – disk shaped organ containing embryonic & maternal blood vessels

Figure Placental circulation Placenta Umbilical cord Chorionic villus containing fetal capillaries Maternal blood pools Uterus Fetal arteriole Fetal venule Umbilical cord Maternal portion of placenta Fetal portion of placenta (chorion) Umbilical arteries Umbilical vein Maternal arteries Maternal veins As placenta forms, HCG levels decline & placenta secretes its own progesterone Fetal nutrients gained from maternal blood pools….no mixing of blood.

child birth is regulated by…. Hormones

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

Contraception Prevent ovulation Prevent sperm from meeting egg

Figure Mechanisms of some contraceptive methods Male Female Method Event 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 Condom Coitus interruptus (very high failure rate) Sperm deposited in vagina Capture of the oocyte by the oviduct Abstinence 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 Implantation of blastocyst in properly prepared endometrium Birth Progestin alone Birth control pills – estrogen & progesterone combo - prevents ovulation by decreasing the release of GnRH which inhibits FSH & LH Morning after pill – higher doses of estrogen & progesterone - prevents fertilization or implantation