Chapter 16 The Reproductive System

1. Chapter 16 The Reproductive System Biology 110 Tri-County Technical College Pendleton, SC

2. Functions • System insures continual existence of human species • ONLY system NOT essential to survival of the individual • Produces, stores, nourishes, and transports functional female and male reproductive cells called gametes

3. Male Reproductive System • Identify and/or label the following components of the male reproductive system: • Penis (shaft, glans, prepuce), testes, epididymis, ductus deferens, seminal vesicles, bulbourethral gland, prostate gland, urethra, and ejaculatory duct

4. Male Visual

5. Male Visual, II

6. Products of Testes…and more • Endocrine products are androgens (most important is testosterone) • Exocrine products are sperm • Semen is mixture of sperm and accessory gland secretions • Secretions supply liquid for transport and nutrition, and contains chemicals that protect sperm and aid their movement

7. More, cont. • Semen is alkaline (pH 7.2-7.6) which helps neutralize acid environment (3.5-4) of female’s vagina • Also contains chemicals that inhibit bacterial multiplication • Dilutes sperm to assist their motility • Ejaculation contains ~ 2-5 mls of semen with 50-130 million sperm per ml

8. More, III • Seminal vesicles located at base of bladder produce ~60% of fluid volume of semen • Thick, yellowish fluid rich in fructose, vitamin C, prostaglandins, & other stuff which nourish & activate sperm passing through tract • Prostate gland (almond) encircles upper prostatic part of urethra just below bladder • secretes milky fluid that helps activates sperm • During ejaculation, fluid enters urethra through several small ducts

9. Last of the More, IV • Bulbourethral glands (pea size), inferior to prostate gland, produce thick, clear mucus that drains into penile urethra • This secretion first to pass down urethra when man becomes sexually excited • Believed to cleanse the urethra of traces of acidic urine and serve as lubricant during sexual intercourse

10. Directions…what are directions? • Seminiferous tubulesrete testis epididymis (20 days, mature and gain ability to swim)ductus deferens ejaculatory duct (passes through prostate) urethra • Main function of ductus deferens to propel sperm from storage sites (epididymis/distal part of ductus deferens into urethra • Ejaculation: thick layers of smooth muscle in DD walls create perisaltic waves that propel sperm • At ejaculation, sperm exit body via urethra

11. Definitions • Penis is male copulatory organ for delivery of sperm into female reproductive tract • Spongy urethra surrounded by 3 areas of erectile tissue that fills with blood during arousal causing penis to enlarge and become erect • Events result in an erection which helps penis serve as penetrating organ to deliver sperm

12. Definitions II • Ejaculation is sudden ejection of semen from the penis • In males, urethra carries both urine and sperm but they never pass at same time • When ejaculation occurs, bladder sphincter constricts • Prevents urine from passing into urethra and also prevents sperm from entering urinary bladder • Circumcision: removal of prepuce (foreskin) from the penis

13. Female Reproductive System • Paired ovaries responsible for manufacturing ova (egg) • Uterine tubes, uterus, & vagina form duct system of female reproductive tract • Uterine (fallopian) tubes receive oocyte and provide site for fertilization • No contact between ovaries & uterine tubes (fimbriae)

14. Female R. S., cont. • Uterus (womb) is hollow organ for receiving, retaining, and nourishing fertilized egg • Body, fundus, and cervix • Vagina (birth canal) provides passageway for delivery of infant, menstrual flow to leave body, and receiving of penis and semen during sexual intercourse (female copulation organ) • External genitalia often called the vulva • mons pubis, libia, clitoris, urethral/vaginal orifices, and greater vestibular glands

15. Female Visual

16. Graafian Follicle/Corpus Luteum • Mature follicle called graafian follicle • Occurs when fluid-filled spaces of secondary follicle fuse to form single fluid-filled antrum • Increases in size, fills with additional fluid forming lump on ovary surfaceblister • Usually only one graafian follicle reaches most advanced development stage and is ovulated • Expands and ruptures forcing small amount of blood and follicular fluid out of vesicle • Secondary oocyte surrounded by cumulus mass and zona pelucide escape from follicle=ovulation

17. Following the Follicle… • After ovulation, ruptured follicle transformed into corpus luteum • Granulosa cells/theca interna (luteal cells) enlarge and begin to secrete progesterone and small amount of estrogen • Will eventually degenerate • If pregnancy occurs, becomes corpus luteum of pregnancy and remains throughout pregnancy • Its progesterone essential for maintaining the placenta until it can begin to make and secrete its own progesterone

18. Ovary Visual

19. The Uterus and its linings • Uterus wall composed of 3 layers • Endometrium is inner layer (mucosa) • Fertilization occurs, embryo burrows into this layer in process called implantation • Embryo/fetus resides there for rest of development • If woman not pregnant, layer sloughs off periodially (~28 days) in process called menses • Occurs in response to changes in levels of ovarian hormones

20. Uterus, cont. • Myometrium is bulky middle layer of interlacing bundles of smooth muscle • Plays active role in delivery of baby by contracting rhythmically • Epimetrium (visceral peritoneum) is outermost serous layer of uterus • Ovulation defined (enough already) as release of ovum (egg) from graafian follicle of the ovary

21. Uterus Visual

22. Regions of the Uterus • Major portion called the body • Superior, rounded portion above entrance of uterine tubes called the fundus • Narrow outlet which protrudes into vagina called the cervix • Cancer of cervix common in women 30-50 • risk factors include frequent cervical inflammations, multiple pregnancies, STDs, active sex life with multiple partners, and age at onset of sexual activity (yearly Pap Smear)

23. Uterus Visual

24. Making Sex Cells…so to speak • Meiosis; somatic cells and sex cells, diploid and haploid, 2N and N • Spermatogenesis: production of sperm from primitive stem cells called spermatogonia • FSH (anterior pituitary) stimulates spermatogonia to divide into Type A (stem) and Type B (primary spermatocyte) cells • Type B cells will undergo meiosis and form 4 sperm

25. Sex Cells, cont. • In spermatogenesis, gametes are called spermatids (sperm) • In last stage of formation, all excess cytoplasm discarded and remaining “stuff” compacted into 3 regions of mature sperm: head, midpiece, and tail • Acrosome located on very tip of head • Entire process takes 64-72 days

26. Spermatogenesis Visual

27. Oogenesis • Oogonia (female stem cells) formed during female fetus development • Daughter cells (primary oocytes) push into ovary connective tissue where they become surrounded by single layer of cells=primary follicles • By time female baby born, oogonia no longer exists, and female’s lifetime supply of primary oocytes already in place in ovarian follicles (~700,000)

28. Oogenesis, cont. • FSH controls ovarian cycle • Follicle grows larger, accumulating fluid in central chamber called antrum • Primary oocyte begins meiosis=2 cells very dissimilar in size • Larger one is secondary oocyte, smaller one is a polar body • LH causes release of secondary oocyte from ovary

29. Oogenesis, cont. • Ovulated secondary oocyte surrounded by its follicle cell capsule now called corona radiata • If secondary fertilized, its nucleus undergoes second meiotic division that produces another polar body and the ovum nucleus • If not fertilized, secondary deteriorates w/o completing meiosis II to form functional egg

30. Oogenesis Visual

31. Sperm Structure • Sperm head contains DNA (essentially the nucleus of the sperm) • Acrosome positioned on tip of head; contains enzymes to help penetrate the egg • Midpiece contains centrioles from which tail (flagellum) arises; mitochondria also located here • Tail (flagellum) for propelling sperm long distance in very short amount of time

32. Hormones are Flowing… • FSH responsible for spermatogenesis in males and maturation of primary follicles in females • LH responsible for testosterone production in males and ovulation in females • Testosterone most important hormonal product of testes • Responsible for development of reproductive organs to adult size, male sex drive, and male secondary sexual characteristics • deepening voice, growth of body hair, enlargement of skeletal muscles, increased heaviness of skeleton

33. Menstrual Cycle Phases • Divided into 3 stages • Menses (1-5): endometrial lining sloughed off and detaches from uterine wall • Accompanied by bleeding for 3-5 days • Detached tissues and blood pass through vagina as menstrual flow • Average blood loss is 50-150 ml (1/4 to ½ cup)

34. Cycles, cont. • Proliferative stage(6-14) endometrium repaired, glands formed in it, and endomertial blood supply is >ing • Stimulated by rising estrogen levels produced by glowing follicles of ovary • Endometrium becomes velvety and thick • Ovulation occurs at end of this stage in response to sudden surge of LH in blood

35. Cycles, cont. • Secretory stage (15-28): rising levels of progesterone (corpus luteum) act on estrogen primed endometrium and > its blood supply even more • Progesterone causes endometrial glands to > in size and begin secreting nutrients into uterine cavity • These nutrients will sustain developing embryo until it can implant

36. Cycles, cont. • Fertilization occurs, embryo produces hormone similar to LH which causes corpus luteum to continue its hormone production • If fertilization does NOT occur, CL begins to degenerate toward end of this period (stage) as LH blood levels begin to decline • Lack of hormones causes blood vessels supplying endometrium to spasm and kink • Deprived of oxygen and nutrients, endometrial cells begin to die which sets stage for menses

37. More definitions, yeah!!!! • Females reach peak reproductive age in late 20s and its downhill from there • Eventually ovulation and menses cease entirely • This event, menopause, considered to have occurred when whole year passes w/o menstruation • Fertilization occurs at moment genetic material from sperm combines with that of ovum to form fertilized egg called a zygote; restores diploid count and forms single cell representing first cell of new individual

38. Definitions, cont. • Embryo: from zygote through 8 weeks • by end, looks human and all organ systems present in rudimentary form • Fetus: from 9 weeks until delivery • Major activities NOW growth and organ specialization accompanied by changes in body proportions

39. Functions of the Placenta • Implantation completed and uterine mucosa grown over burrowed-in embryo by day 14 after ovulation • Trophoblast part of blastocyst develops projections called chorionic villi which cooperate with uterine tissues to form placenta • By 3rd week, placenta functioning to deliver nutrients and oxygen and remove wastes from embryonic blood

40. Functions, cont. • ALL exchanges made through the placental barrier • By end of second month, placenta becomes endocrine organ and is producing estrogen, progesterone, and other hormones to maintain the pregnancy • At this time, corpus luteum of ovary becomes inactive