Sexual reproduction produces new individuals Gametes are sperm & egg

1. Introduction to the Reproductive System • Sexual reproduction produces new individuals • Gametes are sperm & egg • Formed by testes and and ovaries • Fertilization produces one cell (a zygote)with • one set of chromosomes from each parent • Creates genetic variation

2. Introduction to the Reproductive System • Gonads (testes & ovaries) produce gametes & secrete sex hormones • Reproductive systems • Gonads, ducts, glands & supporting structures • Gynecology is study of female reproductive system • Urology is study of urinary system & male reproductive system

3. Male Reproductive System Ejaculatory Duct- sperm and seminal fluid into urethra Seminal vesicle-seminal fluid Ductus deferens- transports sperm Prostate-semen Urethra-urine & semen Penis Epididymis-sperm maturation Testis- sperm formation Scrotum-cools testis

4. Testis • Contains 200 - 300 compartments called lobules • Each lobule contains 2 or 3 seminiferous tubules where sperm are formed • Sperm formation called spermatogenesis Lobule Seminiferous tubule

5. Seminiferous Tubules and Spermatogenesis • Seminiferous tubules contain • Sperm forming cells called spermatocytes that become sperm • Supporting cells called Sertoli cells support sperm and secrete substances important to sperm formation • Interstitial cells in between tubules secrete testosterone Sperm

6. Spermatogenesis • Spermatocytes in seminiferous tubules • Undergo meiosis • Results in four cells with 23 chromosomes • Produces new combinations of genes • Each spermatocyte forms four sperm ( spermatozoa) • Steps are shown on next slide, but may not be enough time to cover it in class

7. SpermatogenesisSperm forming cells go through two meiotic divisions 1°=primary 2°=secondary • Each of four cells develop into sperm • Second division results in four spermatids,each with 23 single stranded chromosomes • First division results in two 2° spermatocytes, each with 23 double stranded chromosomes • Starts with a 2n=46 1° spermatocyte

8. Sperm Structure • Adapted for reaching & fertilizing egg • Head contains DNA & enzymes for penetrating to egg • Midpiece contains mitochondria to form ATP for energy • Tail is flagellum used for locomotion

9. Hormonal Control of Male Physiology Hypothalamus • Hypothalamus secretes gonadotropin releasing hormone (GnRH) • Anterior pituitary secretes FSH and LH • FSH causes Sertoli cells to secrete ABP • LH causes interstitial cells to secrete testosterone • ABP and testosterone stimulate spermatogenesis • Control is Negative FB by testosterone and inhibin GnRh Anterior Pituitary Follicle Stimulating Hormone Luteinizing Hormone Sertoli Cells Interstitial Cells Androgen Binding Protein (ABP) Testosterone Spermatogenesis

10. Semen • Mixture of sperm & seminal fluid • 60% of seminal fluid from seminal vesicles • 30% of seminal fluid from prostate • Semen slightly alkaline • Contains nutrients, clotting proteins & an antibiotic to protect sperm

11. Semen • Typical ejaculate is 2.5 to 5 mL in volume • Normal sperm count is 50 to 150 million/mL • Actions of many sperm are needed for one to enter • If less than 20 million/mL, sterility

12. Erection • Sexual stimulation • Parasympathetic reflex • Dilation of the arterioles supplying penis • Blood enters the penis compressing the veins so that the blood is trapped • Erectile bodies of penis engorge with blood • Erection

13. Emission • Muscle contractions close sphincter at base of bladder • Seminal fluids from seminal vesicles, and prostate gland propelled through ejaculatory duct into urethra in bulb of penis • Sperm from the ductus deferens into urethra in bulb of penis

14. Ejaculation • Stimulated by sympathetic branch of autonomic nervous system • Skeletal muscles around bulb of penis contract rhythmically • Semen propelled out through urethra

15. Female Reproductive System • Ovaries produce eggs (oöcytes) & hormones • Uterine tubes transport fertilized eggs • Uterus where embryonic and fetal development occurs • Vagina or birth canal • External genitalia constitute the vulva • Mammary glands produce milk Uterine Tube Uterus Ovary Vagina Vulva

16. The Ovary • Pair of organs, size of unshelled almonds in upper pelvic region • Histology • Capsule of dense CT • Cortex just deep to capsule contains follicles with egg cells (oöcytes) • Medulla is middle region composed of connective tissue, blood vessels & lymphatics Capsule Capsule

17. Ovarian Follicles • Contain oöcytes (egg cells) in various stages of development • Secrete steroid hormones called estrogens • Growth and repair of uterine lining • Regulation of monthly female cycle • Female sexual characteristics • Maintenance of bones and muscles • Mature (Graafian) follicle releases an oöcyte each month during ovulation

18. Ovarian Follicles • Oöcytes (egg cells) develop within follicles • Stages of folliculardevelopment • Primordial follicle • Single layer of squamous cells around oöcyte • Primary follicle • Layers of cuboidal granulosa cells around oöcyte • Granulosa cells secrete estrogens

19. Ovarian Follicles • Secondary follicle • Antral cavity forms • About 20 form each month from 1° follicles • Normally one 2° follicle becomes a Mature follicle • Mature (Graafian) follicle • Ready to release oöcyte • Ovulation • Follicle ruptures releasing oöcyte oöcyte

20. Corpus Luteum • After ovulation, empty follicle becomes a corpus luteum • Secretes • Progesterone – completes preparation of uterine lining • estrogens work with progesterone • Corpus albicans is white scar left after corpus luteum degenerates

21. Oögenesis – Oögonia to Oöcytes • Potential egg cells called oögonia • In fetus, millions of oögonia produced by mitosis but most degenerate (atresia) • Some develop into immature egg cells called primary oöcytes during fetal development • About 2 million present at birth • 400,000 remain at puberty but only around 400-500 mature during a woman’s life

22. Oögenesis – Primary oöcytes to Secondary oöcytes • Each month, primary oöcytes become secondary oöcytes by completing the first meiotic division • Usually one secondary oöcyte is released (ovulated) from a Mature (Graffian) follicle

23. Oögenesis • Egg forming cells (oöcytes) go through two divisions • 1º = primary • 2º = secondary • Starts with a 2n=46 1ºoöcyte that divides, resulting in two n=23 cells, but one is a large 2º oöcyte and one is a small 1st polar body that may itself divide • Second division only occurs if 2º oöcyte is fertilized. Results in one large n=23 ovum (egg) and one small n=23 2nd polar body • Thus oögenesis results in one large fertilized egg (zygote) and possibly three small polar bodies

24. Oögenesis & Spermatogenesis Compared Spermatogenesis – one cell with 46 chromosomes forms 4 sperm each with 23 chromosomes Oögenesis – one cell with 46 chromosomes forms 1 Egg (ovum) and 3 polar bodies each with 23 chromosomes

25. Female Reproductive Cycle - Monthly Cycle of Changes in Ovary and Uterus • Ovarian cycle • Growth of ovarian follicles • Maturation of oöcyte • Ovulation • Growth of corpus luteum • Secretion of hormones • Uterine (menstrual) cycle • Preparation of uterus to receive embryo • If implantation does not occur, the functional layer of endometrium is shed during menstruation

26. Hormonal Regulation of Female Cycle • Gonadotropin Releasing Hormone (GnRH), secreted by the hypothalamus, controls the female reproductive cycle • Stimulates anterior pituitary to secrete Follicle Stimulating Hormone (FSH) & Luteinizing Hormone (LH)

27. Hormonal Regulation of Female Cycle • FSH & LH target the ovaries and drive the ovarian cycle (monthly changes in the ovary) • Estrogens and progesterone from the ovaries drive the uterine (menstrual) cycle

28. Phases of Ovarian Cycle • Follicular Phase • FSH from anterior pituitary stimulates follicle growth • Follicles grow and a mature (Graafian) follicle is produced • Granulosa cells of follicle secrete estrogens and inhibin • Increasing levels of estrogens and inhibin inhibit FSH • Increasing estrogens then stimulate secretion of LH • Ovulation • LH stimulates release of oöcyte from ovary to pelvic cavity • Uterine tube picks up ovulated oöcyte • Luteal (post-ovulatory) phase • LH stimulates development of corpus luteum from ovulated follicle • Corpus luteum secretes progesterone and estrogens • Progesterone and estrogens prepare endometrium for possible pregnancy

29. Ovarian Cycle Diagram Follicle Stimulating Hormone Luteinizing Hormone Follicular Phase Ovulation Luteal Phase What secretes FSH and LH?

30. Phases of Uterine (Menstrual) Cycle • Menstruation (menses) phase • First few days of 28 day cycle • Decline in progesterone causes functional layer of endometrium to discharge resulting in menstruation • Proliferative phase • Rising levels of estrogens • Growth of functional layer of endometrium to 4-10 mm thickness

31. Phases of Uterine (Menstrual) Cycle • Secretory phase • Corpus luteum of ovary secretes progesterone • Progesterone stimulates • Increased thickening of functional layer to 12-18 mm • Increased blood supply • Growth of endometrial glands • Endometrium now able to support embryo

32. Uterine (Menstrual) Cycle Diagram Estrogens from Ovaries Progesterone and Estrogens from Ovaries

33. Summary of Ovarian and Menstrual Cycles

34. Negative Feedback Controls Cycle • If no pregnancy • Increasing levels of progesterone cause negative feedback • Luteinizing Hormone (LH) inhibited • After about 2 weeks corpus luteum atrophies to corpus albicans (white body) • Progesterone and estrogen levels decline • Functional layer of endometrium discharged in first few days of next cycle

35. Negative Feedback • If no pregnancy continued • With decline in progesterone, estrogens and inhibin secretion • Inhibition of GnRH, FSH and LH stops • Renewed secretion of these hormones starts a new cycle of growth and preparation in ovaries and uterus

36. Negative Feedback Diagram

37. Pregnancy • If pregnancy • Embryo implants in endometrium • Must maintain levels of progesterone to maintain endometrium • Since corpus luteum secretes progesterone, must maintain corpus luteum

38. Pregnancy • LH normally maintains c. luteum, but LH still inhibited by high progesterone levels • What maintains c. luteum during pregnancy? • What was not present before?

39. Ovulation, Fertilization and Implantation • Pick up ovulated oöcyte (secondary oöcyte) • Cilia & peristalsis move oöcyte along • Sperm reaches oöcyte in ampulla of uterine tube • Fertilization occurs within 24 hours after ovulation • Zygote reaches uterus about 4-7 days after ovulation • Implantation in endometrium

40. Pregnancy • The outer part of embryo (the chorion) secretes the hormone human chorionic gonadotropin (hCG) • hCG takes the place of LH and maintains the corpus luteum • After about 3-4 months of pregnancy, corpus luteum degenerates • Placenta now produces its progesterone and estrogens and maintains endometrium Implanted Blastocyst with Embryo Chorion hCG secreted into blood and maintains corpus luteum in ovary

41. Diagram of Pregnancy

42. Mammary Gland • Milk-secreting mammary glands are modified sweat glands • Milk through mammary ducts into lactiferous sinuses • Areola is pigmented area around nipple • Amount of adipose tissue determines breast size • Suspensory (Cooper’s) ligaments suspend breast from fascia of pectoral muscles

43. Mammary Gland Lobule with milk producing cells Lactiferous Duct Lactiferous Sinus Areola Nipple Nipple Areola

44. Physiology of the Breast • Milk production and secretion • Hypothalamus secretes prolactin releasing hormone (PRH) • PRH stimulates anterior pituitary to secrete prolactin • Prolactin, together with some other hormones, causes milk production and secretion from mammary glands

45. Physiology of Mammary Glands • Milk let-down (release from glands) • Nursing stimulates hypothalamus to produce oxytocin • Oxytocin secreted from posterior pituitary • Causes smooth muscles around glands to squeeze milk into mammary ducts and lactiferous sinuses into nipple • Positive feedback

46. Medical Terms May not get to them in lecture. Use them for extra credit.

47. Menstrual Abnormalities • Amenorrhea = absence of menstruation • hormone imbalance, extreme weight loss or low body fat as with rigorous athletic training • Dysmenorrhea = pain associated with menstruation • severe enough to prevent normal functioning • uterine tumors, ovarian cysts, endometriosis or intrauterine device

48. Menstrual Abnormalities • Abnormal uterine bleeding = excessive amount or duration or intermenstrual • fibroid tumors or hormonal imbalance

49. Hysterectomy • Surgical removal of the uterus • Indications for surgery • endometriosis, ovarian cysts, excessive bleeding, cancer of cervix, uterus or ovaries • Complete hysterectomy removes cervix • Radical hysterectomy removes uterus, tubes, ovaries, part of vagina, pelvic lymph nodes and supporting ligaments

50. Circumcision • Removal of prepuce • 3 - 4 days after birth • Possibly lowers UTIs, cancer & sexually transmitted disease