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The Reproductive System

The Reproductive System. The Reproductive System. Gonads—primary sex organs Testes in males Ovaries in females Gonads produce gametes (sex cells) and secrete hormones Sperm—male gametes Ova (eggs)—female gametes. Male Reproductive System Overview. Testes Duct system Epididymis

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The Reproductive System

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  1. The Reproductive System

  2. The Reproductive System • Gonads—primary sex organs • Testes in males • Ovaries in females • Gonads produce gametes (sex cells) and secrete hormones • Sperm—male gametes • Ova (eggs)—female gametes

  3. Male Reproductive System Overview • Testes • Duct system • Epididymis • Ductus (vas) deferens • Urethra

  4. Male Reproductive System Overview • Accessory organs • Seminal vesicles • Prostate • Bulbourethral glands • External genitalia • Penis • Scrotum

  5. Male Reproductive System Figure 16.2a

  6. Male Reproductive System Figure 16.2b

  7. Testes • Olive-sized • Coverings of the testes • Tunica albuginea—capsule that surrounds each testis, fibrous connective tissue • Septa—extensions of the capsule that extend into the testis and divide it into lobules

  8. Testes Figure 16.1

  9. Testes • Each lobule contains one to four seminiferous tubules • Tightly coiled structures • Function as sperm-forming factories • Empty sperm into the rete testis (first part of the duct system) • Sperm travels through the rete testis to the epididymis • Interstitial cells in the seminiferous tubules produce androgens such as testosterone

  10. Testes Figure 16.1

  11. Duct System • Epididymis • Ductus (vas) deferens • Urethra

  12. Epididymis • Comma-shaped, tightly coiled tube • Found on the superior part of the testis and along the posterior lateral side • Functions to mature and store sperm cells (at least 20 days) • Expels sperm with the contraction of muscles in the epididymis walls to the vas deferens • About 6m long

  13. Epididymis Figure 16.1

  14. Ductus Deferens (Vas Deferens) • Carries sperm from the epididymis to the ejaculatory duct • Passes through the inguinal canal and over the bladder • Moves sperm by peristalsis(wave like motion of smooth muscles) • Spermatic cord—ductus deferens, blood vessels, and nerves in a connective tissue sheath

  15. Ductus Deferens (Vas Deferens) Figure 16.1

  16. Ductus Deferens (Vas Deferens) • Ends in the ejaculatory duct which unites with the urethra • Expanded end is called the ampulla • Ejaculation—smooth muscle in the walls of the ductus deferens create peristaltic waves to squeeze sperm forward • Vasectomy • cutting of the ductus deferens at the level of the testes to prevent transportation of sperm • Sperm is still produced, but they eventually deteriorate and are reabsorbed.

  17. Urethra • Extends from the base of the urinary bladder to the tip of the penis • Carries both urine and sperm • Sperm enters from the ejaculatory duct

  18. Urethra • Regions of the urethra • Prostatic urethra—surrounded by prostate • Membranous urethra—from prostatic urethra to penis • Spongy (penile) urethra—runs the length of the penis

  19. Urethra Figure 16.2b

  20. Accessory Organs • Seminal vesicles • Prostate • Bulbourethral glands

  21. Accessory Organs Figure 16.2b

  22. Seminal Vesicles • Located at the base of the bladder • Produces a thick, yellowish secretion (60% of semen) • Fructose (sugar) • Vitamin C • Prostaglandins • Other substances that nourish and activate sperm

  23. Accessory Organs Figure 16.2b

  24. Prostate • Size and shape of a chestnut • Encircles the upper part of the urethra • Secretes a milky fluid • Helps to activate sperm • Enters the urethra through several small ducts

  25. Prostate • Reputation as a health destroyer • Hyertrophy (enlargement) – affects nearly every elderly male. • Difficulty urinating, bladder infections, kidney damage, cancer

  26. Prostate Figure 16.2a

  27. Bulbourethral Glands • Pea-sized gland inferior to the prostate • Produces a thick, clear mucus • Cleanses the urethra of acidic urine • Serves as a lubricant during sexual intercourse • Secreted into the penile urethra

  28. Bulbourethral Glands Figure 16.2a

  29. Semen • Mixture of sperm and accessory gland secretions • Advantages of accessory gland secretions • Fructose provides energy for sperm cells • Alkalinity of semen helps neutralize the acidic environment of vagina • Semen inhibits bacterial multiplication • Elements of semen enhance sperm motility • 2-5mL of semen propelled during ejaculation • Contains 50-130 million sperm per mL

  30. Semen • Male infertility • Commonly caused by a problem with semen. • Sperm count, motility and morphology, semen volume, pH, fructose content

  31. External Genitalia • Scrotum • Penis

  32. External Genitalia Figure 16.2a

  33. External Genitalia • Scrotum • Divided sac of skin outside the abdomen • Maintains testes at 3°C(about 5.5ºF) lower than normal body temperature to protect sperm viability • When it is cold out side the skin will become highly wrinkled and pull the testes closer to the body to be able to maintain temperature.

  34. External Genitalia • Penis • Delivers sperm into the female reproductive tract • Regions of the penis • Shaft • Glans penis (enlarged tip) • Prepuce (foreskin) • Folded cuff of skin around proximal end • Often removed by circumcision

  35. External Genitalia Figure 16.2a

  36. External Genitalia • Internally there are three areas of spongy erectile tissue around the urethra • Erections occur when this erectile tissue fills with blood during sexual excitement

  37. External Genitalia Figure 16.1

  38. McGraw-Hill video • http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120112/anim0043.swf::Spermatogenesis

  39. Spermatogenesis • Production of sperm cells • Begins at puberty and continues throughout life • Occurs in the seminiferous tubules

  40. Spermatogenesis Figure 16.3

  41. Spermatogenesis Figure 16.3 (1 of 2)

  42. Spermatogenesis Figure 16.3 (2 of 2)

  43. Spermatogenesis • Spermatogonia (stem cells) undergo rapid mitosis to produce more stem cells before puberty • Found on the outer edge of tubule • Follicle-stimulating hormone (FSH) is secreted by pituitary gland and modifies spermatogonia division • One cell produced is a stem cell, called a type A daughter cell • Stays at the tubule periphery • The other cell produced becomes a primary spermatocyte, called a type B daughter cell • Gets pushed toward the lumen

  44. Spermatogenesis • Primary spermatocytes undergo meiosis • Meiosis only happens in the gonads. • One primary spermatocyte produces four haploid spermatids • Spermatids—23 chromosomes (half as much material as other body cells)

  45. Human Life Cycle • Union of a sperm (23 chromosomes) with an egg (23 chromosomes) creates a zygote (2n or 46 chromosomes)

  46. Human Life Cycle Figure 16.4

  47. Spermiogenesis • Late spermatids are produced with distinct regions • Head • Midpiece • Tail • Spermiogenesis – last stage of sperm development. • Excess cytoplasm is stripped away • Sperm cells result after maturing of spermatids • Spermatogenesis (entire process, including spermiogenesis) takes 64 to 72 days

  48. Structure of a Sperm Figure 16.5b

  49. Structure of a Sperm Figure 16.5a

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