1. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint ® Lecture Slides prepared by Vince Austin, Bluegrass Technical and Community College C H A P T E R 26 The Reproductive System P A R T A

2. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Reproductive System  Primary sex organs (gonads) – testes in males, ovaries in females  Gonads produce sex cells called gametes and secrete sex hormones  Accessory reproductive organs – ducts, glands, and external genitalia  Sex hormones – androgens (males), and estrogens and progesterone (females)

3. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Reproductive System  Sex hormones play roles in:  The development and function of the reproductive organs  Sexual behavior and drives  The growth and development of many other organs and tissues

4. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Male Reproductive System  The male gonads (testes) produce sperm and lie within the scrotum  Sperm are delivered to the exterior through a system of ducts: epididymis, ductus deferens, ejaculatory duct, and the urethra  Accessory sex glands:  Empty their secretions into the ducts during ejaculation  Include the seminal vesicles, prostate gland, and bulbourethral glands

5. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Male Reproductive System Figure 27.1

6. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Testes  Septa divide the testis into 250-300 lobules, each containing 1-4 seminiferous tubules

7. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Testes  Seminiferous tubules:  Produce the sperm  Converge to form the tubulus rectus  The straight tubulus rectus conveys sperm to the testis

8. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Testes  Surrounding the seminiferous tubules are interstitial cells that produce androgens (hormones)  From the testis, the sperm:  Leave the testis via efferent ductules  Enter the epididymis

9. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Testes Figure 27.3a

10. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Spermiogenesis: Spermatids to Sperm  Sperm have three major regions  Head – contains DNA and has a helmetlike acrosome containing hydrolytic enzymes that allow the sperm to penetrate and enter the egg  Midpiece – contains mitochondria spiraled around the tail filaments  Tail – a typical flagellum produced by a centriole

11. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Spermatogenesis  The sequence of events that produces sperm in the seminiferous tubules of the testes  Each cell has two sets of chromosomes (one maternal, one paternal) and is said to be diploid (2n chromosomal number)  Humans have 23 pairs of homologous chromosomes  Gametes only have 23 chromosomes and are said to be haploid (n chromosomal number)  Gamete formation is by meiosis, in which the number of chromosomes is halved (from 2n to n)

12. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Spermatogenesis  Cells making up the walls of seminiferous tubules are in various stages of cell division  These spermatogenic cells give rise to sperm in a series of events  Mitosis of spermatogonia, forming spermatocytes  Meiosis forms spermatids from spermatocytes  Spermiogenesis – spermatids form sperm

13. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 27.8b, c

14. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Spermiogenesis: Spermatids to Sperm  Late in spermatogenesis, spermatids are haploid but nonmotile  Spermiogenesis – spermatids lose excess cytoplasm and form a tail, becoming sperm

15. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Spermiogenesis: Spermatids to Sperm Figure 27.9a

16. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epididymis  Its head joins the efferent ductules and caps the superior aspect of the testis  The duct of the epididymis has cilia that:  Absorb testicular fluid  Pass nutrients to the sperm  Nonmotile sperm enter, pass through its tubes and become motile

17. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vas Deferens  A muscular tube 45 cm in length leading from the epididymus up into the body cavity to the ejaculatory duct, where it unites and empties its contents into the urethra.

18. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Glands: Seminal Vesicles  Lie on the posterior wall of the bladder and secrete 60% of the volume of semen  Join the ductus deferens to form the ejaculatory duct  Semen – viscous alkaline fluid containing fructose (to nourish sperm), ascorbic acid, coagulating enzyme (vesiculase), and prostaglandins (causes contractions in female tract to help propel sperm to egg)

19. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Glands: Prostate Gland  Chestnut-shaped gland that encircles part of the urethra inferior to the bladder  Its milky, slightly acid fluid, which enhances the mobility of sperm cells and neutralizes the acidity of the by-products produced during spermatogenesis and the acidity of the female reproductive tract.  Plays a role in the activation of sperm

20. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Glands: Bulbourethral Glands (Cowper’s Glands)  Pea-sized glands inferior to the prostate  Produce thick, clear mucus prior to ejaculation that neutralizes traces of acidic urine in the urethra and lubricates the tip of the penis during sexual arousal.

21. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Semen  Milky white, sticky mixture of sperm and accessory gland secretions  Provides a transport medium and nutrients (fructose), protects and activates sperm, and facilitates their movement  Prostaglandins in semen:  Decrease the viscosity of mucus in the cervix  Stimulate reverse peristalsis in the uterus  Facilitate the movement of sperm through the female reproductive tract

22. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Semen  The hormone relaxin enhances sperm motility  The relative alkalinity of semen neutralizes the acid environment found in the male urethra and female vagina  Seminalplasmin – antibiotic chemical that destroys certain bacteria  Only 2-5 ml of semen are ejaculated, but it contains 50-130 million sperm/ml

23. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Scrotum  Sac of skin and superficial fascia that hangs outside the abdominopelvic cavity at the root of the penis  Contains paired testicles separated by a midline septum  Its external positioning keeps the testes 3  C lower than core body temperature (needed for sperm production)

24. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Scrotum Figure 27.2

25. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Penis  A copulatory organ designed to deliver sperm into the female reproductive tract  It is designed to deliver both semen and urine to the outside.  Erection – during sexual excitement, the erectile tissue fills with blood, caused by a parasympathetic impulse, causing the penis to enlarge and become rigid

26. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Penis Figure 27.4

27. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Brain-Testicular Axis  Hormonal regulation of spermatogenesis and testicular androgen production involving the hypothalamus, anterior pituitary gland, and the testes

28. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Brain-Testicular Axis  Testicular regulation involves three sets of hormones:  GnRH, which indirectly stimulates the testes through:  Follicle stimulating hormone (FSH)- stimulates the supporting cells of the seminiferous tubules.  Luteinizing hormone (LH)- promotes the development of interstitial cells of the testes and they, in turn, secrete male hormones (testosterone).  FSH & Testosterone stimulate spermatogenesis  Gonadotropins, which directly stimulate the testes  Testicular hormones, which exert negative feedback controls

29. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Male Sex Hormones  Testosterone (angrogens) is secreted in a fetus until birth, and then not again until puberty, after which it is continuously secreted.  Testosterone stimulates the development of the male reproductive organs and causes the testes to descend.  Testosterone is also responsible for male secondary sex characteristics (deep voice, body hair, thickening of the skin, and so forth)

30. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Regulation of Testicular Function  Feedback inhibition on the hypothalamus and pituitary results from:  Rising levels of testosterone  Increased inhibin Figure 27.10

31. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanism and Effects of Testosterone Activity  Testosterone is synthesized from cholesterol  It must be transformed to exert its effects on some target cells  Testosterone targets all accessory organs and its deficiency causes these organs to atrophy  Testosterone is the basis of libido in both males and females