1. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Reproductive system

2. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Regulation of Reproduction  Hypothalamus: pulse generator  Gonadotropin releasing hormone (GnRH)  Anterior pituitary  Luteinizing hormone (LH)  Follicle stimulating hormone (FSH)  Gonads produce steroid and peptide hormones  Gonads are the main source of sex steroids  Peptide hormones: inhibin and activin

3. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Feedback Loops Control Gonadotropin Release Internal and environmental stimuli CNS Hypothalamus Anterior pituitary Steroid and peptide hormones Gamete production GnRH Short-loop negative feedback Long-loop feedback may be negative or positive Stimulus Integrating center Efferent pathway Effector Tissue response LH Endocrine cells FSH Gonads (ovaries or testes) KEY Females only

4. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Synthesis Pathways for Steroid Hormones Cholesterol Progesterone Testosterone Dihydro- testosterone (DHT) aromatase EstradiolCorticosteroneCortisol Aldosterone Intermediate steps

5. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Male Reproductive System – overview of structures  The male gonads (testes) produce sperm  Sperms are delivered to the exterior through a system of ducts:  epididymis,  ductus deferens,  ejaculatory duct  urethra  Accessory sex glands:  seminal vesicles, prostate gland, and bulbourethral glands

6. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Protection of the testis  The outermost protection is the scrotum  A sac of skin and superficial fascia that hangs outside the abdominopelvic cavity at the root of the penis  Separated by a midline septum  Its external positioning keeps the testes 3oC lower than core body temperature (needed for sperm production)  Each testis is surrounded by two tunics:  The tunica vaginalis, derived from peritoneum  The tunica albuginea, the fibrous capsule of the testis

7. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Testes protection - Testicular Thermoregulation  Sperms are not produced at core body temperature  In the scrotum, the testes are kept 2-3°C cooler than in the pelvic cavity. This is essential for sperm production.  Cooling mechanisms  The cremaster muscle contains strips of the internal abdominal oblique muscle around the spermatic cord.  It can elevate or lower the testes.  The dartos muscle is a subcutaneous layer of smooth muscle that wrinkles skin reducing surface area of scrotum. Can lifts testis upwards  The pampiniform plexus is an extensive network of veins that surround the testicular artery in the spermatic cord, keeping the testes cooler countercurrent heat exchange that cools arterial blood entering testis

8. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Countercurrent Heat Exchanger

9. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Testes  Divided to 250-300 lobules by septa  each lobule contains 1-4 seminiferous tubules  Seminiferous tubules:  Produce the sperm

10. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Cells in the testes – 3 types  2 populations found in the Seminiferous tubule  Germinal epithelium – lines the lumen of the tubules  consisting of several layers of germ cells in the process of becoming sperm  Sustentacular (Sertoli) cells.  Between the seminiferous tubules are clusters of interstitial (Leydig) cells, the source of testosterone (will be discussed later with hormonal control).

11. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

12. The functions of Sertoli cells and BTB  Sertoli cells protect the germ cells and promote their development. Tight junctions between adjacent sustentacular cells form a blood-testis barrier (BTB)  The fluid inside the tubules contains high levels of androgens, potassium and amino acids  The BTB prevents the immune system from attacking the developing spermatozoa (contain specific Ag that are not found on any other cell)  Sertoli cell supply nutrients to the developing sperms  Phagocytize cytoplasm shed by spermatids  Secrete inhibin - negative feedback loop for FSH  Secrete androgen-binding-protein (ABP) – binds testosterone inside tubules to maintain high levels

13. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Meiosis in general and Spermatogenesis – production of sperms

14. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings MALEFEMALE Spermatids develop into MITOSIS STAGE OF CELL DIVISION 46 (diploid) Sister chromatids MEIOSIS Second meiotic division Secondary gamete divides. 23 chromosomes (haploid) First meiotic division Primary gamete divides into two secondary gametes. 23 chromosomes, duplicated Spermatogonia Oögonium Secondary oocyte (egg) Disintegrates Second polar body disintegrates. Zygote Sperm Oögonia Secondary spermatocytes (may not occur) Egg released from ovary at ovulation. Primary spermatocyte Spermatogonium One primary spermatocyte yields 4 sperm. One primary oocyte yields 1 egg. Primary oocyte FERTILIZATION Unfertilized egg passes out of body. First polar body Germ cell proliferation 46 chromosomes per cell (only two shown here) DNA replicates but no cell division. 46 chromosomes, duplicated Embryo Reproductive adult 1 2 3 4 5 6 Figure 26-5, steps 1–6 Ovulation with Fertilization Is Followed by Final Step of Meiosis

15. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 28-6b Chromosomes in Mitosis and Meiosis Meiosis. The fates of three representative chromosome pairs during the two stages of meiosis Chromosomes Tetrad Cell Chromosome duplication, synapsis, and tetrad formation Meiosis I Meiosis II Chromosomes of gametes Gametes 1 2 3 4 1 2 34

16. 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 sperms in a series of events  Mitosis of spermatogonia, forming spermatocytes  Meiosis forms spermatids from spermatocytes  Spermiogenesis – spermatids to sperm

17. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings http://distance.stcc.edu/AandP/AP/AP2pages/reprod/spermato.htm spermatogenesis spermiogenesis  Spermiogenesis – spermatids lose excess cytoplasm and form a tail, becoming sperm Spermiogenesis: Spermatids to Sperm

18. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mitosis of Spermatogonia  Spermatogonia – outermost cells in contact with the epithelial basal lamina  Spermatogenesis begins at puberty as each mitotic division of spermatogonia results in type A or type B daughter cells  Type A cells remain at the basement membrane and maintain the germ line  Type B cells move toward the lumen and become primary spermatocytes

19. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Spermatozoa structure  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

20. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Regulation of Testicular Function  The hypothalamus releases gonadotropin-releasing hormone (GnRH)  GnRH stimulates the anterior pituitary to secrete FSH and LH  FSH causes sustentacular cells to release androgen- binding protein (ABP)  LH stimulates interstitial cells to release testosterone  ABP binding of testosterone enhances spermatogenesis

21. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 27.9 Anterior pituitary Inhibin GnRH Testosterone Via portal blood Interstitial cells Sustentacular cell Spermatogenic cells Seminiferous tubule Somatic and psychological effects at other body sites LH FSH 1 2 2 3 4 5 6 78 Stimulates Inhibits

22. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings LH GnRH Hypothalamus Anterior pituitary Inhibin Testes Leydig cells Testosterone (T) To body for secondary effects FSH Sertoli cell Cell products Second messenger Sertoli cell ABPT Androgen-binding protein (ABP) Spermatogonium Spermatocyte Figure 26-11 (9 of 9) Testosterone Inhibits the Hypothalamus and Anterior Pituitary

23. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Testosterone  The principal androgen (male sex hormone) is testosterone.  This steroid is manufactured by the interstitial (Leydig) cells of the testes.  Secretion of testosterone increases sharply at puberty and is responsible for the development of the secondary sexual characteristics of men.  Testosterone is also essential for the production of sperm.

24. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 22.2 Effects of Androgens gonads and Secondary Sex Characteristics

25. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Spermatic Ducts  Epididymis (head, body and tail)  6 m long coiled duct adhering to posterior of testis  site of sperm maturation and storage (fertile for 60 days)  Ductus deferens/vas deferens (peristalsis during orgasm)  muscular tube 45 cm long passing up from scrotum through inguinal canal to posterior surface of bladder  Ejaculatory duct  2 cm duct formed from ductus deferens and seminal vesicle and passing through prostate to empty into urethra  Spermatic cord – encloses PNS and SNS nerve fibers, blood vessels, and lymphatics that supply the testes

26. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epididymis functions  The duct of the epididymis has stereocilia that:  Absorb testicular fluid  Pass nutrients to the sperm  Recycling center for damaged spermatozoa  Storage place for spermatozoa  Facilitate functional maturation preparing them for fertilization:  Plasma membrane changes, alterations in acrosomal membrane

27. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Connection between testis and the body  The structures that connect the testis with the body are enclosed within a connective tissue sheath called the spermatic cord  Blood vessels  Nerve fibers  Vas deferens  Cremaster muscle

28. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Urethra  Conveys both urine and semen  Consists of three regions  Prostatic – portion surrounded by the prostate  Membranous – lies in the urogenital diaphragm  Spongy, or penile – runs through the penis and opens to the outside at the external urethral orifice

29. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Glands: Seminal Vesicles  secrete 60% of the volume of semen  The composition of the gland secretions include:  High concentration of fructose that is easily metabolized by spermatozoa  Prostaglandins that stimulate smooth muscle contractions in both male and female reproductive tract  Fibrinogen that forms temporary clot within the vagina after ejaculation  When the inactive sperms mix with the seminal fluid they undergo the first step of activation and the flagella start moving (in some book this is done by the help of the prostate)  The secretion of the seminal gland are discharged into the ejaculatory duct under the control of the sympathetic system

30. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Glands: Prostate Gland  Doughnut-shaped gland that encircles part of the urethra inferior to the bladder  Slightly acidic  Produces 20-30% of the semen volume  Seminalplasmin – prostatic enzyme that kills bacteria  Prostatic enzyme that coagulates semen within minutes after ejaculation (converts fibrinogen to fibrin)  Contains citrate (nutrient source) and enzymes

31. 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

32. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings semen  The combination of spermatozoa and fluids from accessory glands  A typical ejaculation – 2-5 ml  Normal sperm count – 20-100 million/ml  Enzymes in semen:  Protease – help dissolve mucus in vagina  Seminalplasmin – prostatic enzyme that kills bacteria  Prostatic enzyme that coagulates semen within minutes after ejaculation (converts fibrinogen to fibrin)  Fibrinolysin – breaks fibrinogen and allows semen to become liquid again

33. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Glands Contribute to Semen

34. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Penis  A copulatory organ designed to deliver sperm into the female reproductive tract  Erectile tissue – spongy network of connective tissue and smooth muscle with vascular spaces  Corpus spongiosum – surrounds the urethra and expands to form the glans and bulb of the penis  Corpora cavernosa – paired dorsal erectile bodies bound by fibrous tunica albuginea  Erection – during sexual excitement, the erectile tissue fills with blood causing the penis to enlarge and become rigid