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The Reproductive System

The Reproductive System. The Reproductive System. Purpose is to promote survival of the species 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.

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The Reproductive System

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  1. The Reproductive System

  2. The Reproductive System • Purpose is to promote survival of the species • 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 • Function • Exocrine- sperm producing function • Endocrine- testosterone producing function • Suspended in pouch called the scrotum • Contains testes and epididymis • Divided by a septum • Keeps sperm 3 degrees Celsius below body temperature • Subject to traumatic injury

  8. Testes • Coverings of the testes • Tunica albuginea—capsule that surrounds each testis • Septa—extensions of the capsule that extend into the testis and divide it into lobules

  9. Testes Figure 16.1

  10. 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

  11. Testes Figure 16.1

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

  13. 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) • during this time, they mature and gain the ability to swim • Expels sperm with the contraction of muscles in the epididymis walls to the vas deferens

  14. Epididymis Figure 16.1

  15. 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 • Spermatic cord—ductus deferens, blood vessels, and nerves in a connective tissue sheath

  16. Ductus Deferens (Vas Deferens) Figure 16.1

  17. 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

  18. Urethra • Extends from the base of the urinary bladder to the tip of the penis • Carries both urine and sperm, but not at same time • Sperm enters from the ejaculatory duct and the bladder sphincter constricts

  19. 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

  20. Parts of the Urethra

  21. Urethra Figure 16.2b

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

  23. Accessory Organs Figure 16.2b

  24. 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

  25. Accessory Organs Figure 16.2b

  26. Prostate • Doughnut shaped gland • Encircles the upper part of the urethra • Secretes a milky fluid • Helps to activate sperm • Enters the urethra through several small ducts

  27. Prostate Figure 16.2a

  28. Prostate Gland • Hypertrophy of Prostate • Very common • Makes urination difficult • Leads to bladder and kidney infections • Prostatitis • Inflammation of the prostate • Single most common reason for a man to consult a urologist

  29. Prostate Gland • Prostatic Cancer • Third most prevalent cancer • Most common cancer in men • Early detection is critical • PSA test

  30. Bulbourethral Glands Figure 16.2a

  31. 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

  32. 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 • Amount of ejaculation is about 1 tsp.

  33. Male Infertility • Can be caused by obstruction of the duct system • Hormonal imbalances • Environmental estrogens • Pesticides • Excessive alcohol • Antibodies made by some men against their own sperm

  34. Male Infertility • First step in treatment is semen analysis • Sperm count • Need 20 million per mililiter • Motility • Morphology (shape and maturity) • Semen volume • Ph • Fructose content

  35. Male Infertility • Infertility- abnormally low ability to produce • Sterility- complete inability to reproduce • Oligospermia- decreased sperm count • Oligospermia can be caused by • Infection • Fever • Radiation • Malnutrition • High temperature in testes

  36. External Genitalia • Scrotum • Penis

  37. External Genitalia Figure 16.2a

  38. External Genitalia • Scrotum • Divided sac of skin outside the abdomen • Maintains testes at 3°C lower than normal body temperature to protect sperm viability

  39. 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

  40. External Genitalia Figure 16.2a

  41. 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

  42. External Genitalia Figure 16.1

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

  44. Spermatogenesis Figure 16.3

  45. Spermatogenesis Figure 16.3 (1 of 2)

  46. Spermatogenesis Figure 16.3 (2 of 2)

  47. Spermatogenesis • Spermatogonia (stem cells) undergo rapid mitosis to produce more stem cells before puberty • Follicle-stimulating hormone (FSH) modifies spermatogonia division • One cell produced is a stem cell, called a type A daughter cell • The other cell produced becomes a primary spermatocyte, called a type B daughter cell

  48. Spermatogenesis • Primary spermatocytes undergo meiosis • One primary spermatocyte produces four haploid spermatids • Spermatids—23 chromosomes (half as much material as other body cells)

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

  50. Human Life Cycle Figure 16.4

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