Chapter 16 – Part 1 The Reproductive System

1. Chapter 16 – Part 1The Reproductive System

2. Function of the Reproductive System • Reproductive Systems – Purpose of both (female and male) systems is to produce offspring • Reproductive roles: • Male – Manufacture male gametes (sperm) and deliver them to the female reproductive tract • Female – Produce female gametes (eggs or ova)

3. Division of the Reproductive System • Primary sex organs (testes and ovaries) • Accessory reproductive organs

4. The Reproductive System • Gonads – primary sex organs • Includes the: • Testes in males • Ovaries in females • Gonads produce gametes (sex cells) and secrete hormones • Gametes include: • Sperm – male gametes • Ova (eggs) – female gametes

5. Division of the Male Reproductive System • Primary Reproductive Organ • Includes the Testes (male gonads) • Have a sperm-producing and testosterone-producing function • Accessory Reproductive Structures • Includes ducts or glands • Aid in the delivery of the sperm to the body exterior or to the female reproductive tract

6. Coverings of the Testes • Each olive sized testis is about 1 ½ inches long and 1 inch wide • Tunica albuginea – fibrous connective tissue capsule that surrounds each testis

7. Coverings of the Testes • Septa – extensions of the tunica albuginea that extend into the testis and divide it into a large number of lobules

8. Testes • Each lobule contains one to four tightly coiled seminiferous tubules • Function as “sperm-forming factories” • Empty sperm into another set of tubules called the rete testis (located on one side of the testis) • Sperm travels through the rete testis to enter the first part of the duct system, the epididymis

9. Testes

10. Testes • Lying in the soft connective tissue surrounding the seminiferous vesicles are the interstitial cells • Interstitial cells produce testosterone

11. Overview of the Male Anatomy: Duct System • Male duct system transports sperm from the body • Male duct system includes: • Epididymis • Ductus deferens • Urethra

12. Epididymis • Comma-shaped • Tightly coiled tube about 20 feet long • Caps the superior part of the testis and then runs down its posterior lateral side • 1st part of the male duct system

13. Epididymis • Function: Temporary storage site for the immature sperm that enter it from the testis • While the sperm make their way along the snaking course of the epididymis (a trip that takes about 20 days), they mature and gain the ability to swim • When a male is sexually stimulated, the walls of the epididymis contract to expel sperm into the ductus deferens

14. Ductus Deferens (Vas Deferens) • The ductus deferens or vas deferens runs upward from the epididymis through the inguinal canal into the pelvic cavity and arches over the superior aspect of the bladder

15. Ductus Deferens (Vas Deferens) • The vas deferens is enclosed, along with blood vessels and nerves, in a connective tissue sheath called the spermatic cord. • The end of the ductus deferens empties into the ejaculatory duct, which unites with the urethra.

16. Ductus Deferens (Vas Deferens) • Main Function: Propel live sperm from their storage sites(epididymis and distal part of the ductus deferens) to the ejaculatory duct and into the urethra • At the moment of ejaculation, the thick layers of smooth muscle move the sperm by peristalsis

17. Vasectomy • Vasectomy – Cutting of the ductus deferens at the level of the testes to prevent transportation of sperm • Part of the ductus deferens lies in the scrotal sac, which hangs outside the body cavity • Relatively minor operation - the surgeon makes a small incision into the scrotum and then cuts through or cauterizes the ductus deferens • Birth control method

18. Results of a Vasectomy • Sperm are still produced, but they can no longer reach the body exterior • Eventually the sperm deteriorate and are reabsorbed • A man is sterile after this procedure • Because testosterone is still produced, the sex drive and secondary sex characteristics are retained

19. Urethra • Urethra - Extends from the base of the urinary bladder to the tip of the penis • Terminal part of the male duct system • Carries both urine and sperm (serves the reproductive system and the urinary system) • However, urine and sperm never pass at the same time • When ejaculation occurs and sperm enter from the ejaculatory duct, the bladder sphincter prevents the passage of urine into the urethra

20. Regions of the Urethra Prostatic urethra –surrounded by the prostate gland Membranous urethra – spans the distance from the prostatic urethra to the penis Spongy (penile) urethra – runs within the length of the penis

21. Urethra

22. Accessory Glands and Semen • Accessory organs include: • Paired seminal vesicles • Prostate gland • Bulbourethral glands • These glands produce the bulk of semen, the sperm-containing fluid that is expelled out of the male’s reproductive tract during ejaculation.

23. The Seminal Vesicles • The seminal vesicles are located at the base of the bladder • Produces about 60% of the fluid volume of semen • Produces a thick, yellowish secretion • Is rich in sugar (fructose), vitamin C, prostaglandins, and other substances, which nourish and activate the sperm passing through the tract

24. The Seminal Vesicles • The duct of each seminal vesicle joins the ductus deferens on the same side to form the ejaculatory duct • Thus, sperm and seminal fluid enter the urethra together during ejaculation

25. Prostate Gland • Prostate Gland - Single gland about the size and shape of a chestnut • Secretes a milky fluid • Plays a role in activating sperm • During ejaculation, it enters the urethra through several small ducts

26. Prostate Gland • Encircles the upper part of the urethra just below the bladder • Its size and texture can be palpated (felt) by digital (finger) examination through the anterior rectal wall.

27. Enlarged Prostate Gland • Hypertrophy (enlargement) of the prostate gland affects nearly every elderly male • This strangles the urethra and leads to: • Difficulty urinating • An enhanced risk of bladder infections and kidney damage • Treatment: Surgery, drugs or microwaves to shrink the prostate, small inflatable balloon to compress the tissue, needle that emits radiation

28. Enlarged Prostate Gland Facts • Inflammation of the prostate is the single most common reason for a man to consult a urologist • Prostatic cancer is the third most prevalent cancer in men • Is generally a slow- growing hidden condition • Can also be a swift and deadly killer

29. Bulbourethral Glands • Bulbourethral Glands – Tiny, pea-sized glands inferior to the prostate gland • Produces a thick, clear mucus which drains into the penile urethra • This secretion is the first to pass down the urethra when a man becomes sexually excited • Purposes: Cleanses the urethra of acidic urine and serves as a lubricant during sexual intercourse

30. Semen • Semen – Milky white, somewhat sticky mixture of sperm and accessory gland secretions • Functions: Provides a transport medium and nutrients and contains chemicals that protect the sperm and aid in movement

31. Semen • Advantages of accessory gland secretions • Fructose provides energy for sperm cells • Alkalinity of semen helps neutralize the acidic environment of the female’s vagina, (sperm are sluggish under acidic conditions) • Semen inhibits bacterial multiplication • Elements of semen enhance sperm motility • Hormones and enzymes enhance sperm motility • Semen also dilutes sperm, which assists with motility

32. Semen • The amount of semen propelled out of the male duct system during ejaculation is relatively small - only 1-5 milliliter (about 1 teaspoon) • However, there are between 50-130 million sperm in each milliliter of semen!

33. Male Infertility • Male infertility may be caused by: • Obstructions of the duct system • Hormonal imbalances • Environmental estrogens • Pesticides • Excessive alcohol • Many other factors

34. Male Infertility • One of the first series of tests done when a couple has been unable to conceive is semen analysis • Factors analyzed include sperm count, motility and morphology (shape and maturity), semen volume, pH, and fructose content • A sperm count lower than 20 million per milliliter makes impregnation improbable

35. External Genitalia • External genitalia include: • Penis • Scrotum

36. External Genitalia: Scrotum • Scrotum - Divided sac of skin that hangs outside the abdominal cavity, between the legs and at the root of the penis

37. External Genitalia: Scrotum • Maintains testes at 3°C (37.4°F) lower than normal body temperature to protect sperm viability • Changes in scrotal surface area can maintain a temperature that favors viable sperm production • Under normal conditions: The scrotum hangs loosely, providing the testes with a temperature that is below body temperature • When the external temperature is very cold: The scrotum becomes heavily wrinkled as it pulls the testes closer to the warmth of the body wall

38. External Genitalia: Penis • Penis - Delivers sperm into the female reproductive tract • Covered by loose skin • Regions of the penis: • Shaft • Glans penis - enlarged tip • Prepuce(Foreskin) - Folded cuff of skin around the proximal end of the glans

39. External Genitalia: Penis

40. External Genitalia: Circumcision • Frequently, the foreskin is surgically removed shortly after birth, by a procedure called circumcision.

41. External Genitalia: Erection • Internally there are three areas of spongy erectile tissue around the urethra • The spongy tissue fills with blood during sexual excitement • This causes an erection, where the penis becomes enlarged and rigid • Helps the penis serve as a penetrating organ to deliver the semen into the female’s reproductive tract