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

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)

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

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.

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)

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

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.

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

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 million sperm/ml

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)

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

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

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

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

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

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)

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

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