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Anatomy and Physiology of the Male

Anatomy and Physiology of the Male. Topics. Anatomy Physiology Spermatogenesis Hormonal regulation Development. Anatomy. Scrotum Testes Penis Glands. Scrotum. Maintains 34°C (93.2°F) Dartos muscle – wrinkles the skin Cremaster muscles – draw scrotum toward abdomen. Testes.

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Anatomy and Physiology of the Male

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  1. Anatomy and Physiology of the Male

  2. Topics • Anatomy • Physiology • Spermatogenesis • Hormonal regulation • Development

  3. Anatomy • Scrotum • Testes • Penis • Glands

  4. Scrotum • Maintains 34°C (93.2°F) • Dartos muscle – wrinkles the skin • Cremaster muscles – draw scrotum toward abdomen

  5. Testes • Coverings • Tunica vaginalis • Tunica albuginea • Lobules • Seminiferous tubules • Tubulus rectus • Rete testis • Epididymis

  6. Testes Blood Supply • Countercurrent heat exchange • Testicular artery • Pampiniform venous plexus

  7. Testes Blood Supply • Varicocele • Varicose vein like condition • 15-20% of males • 40% of infertile males

  8. Penis external anatomy • Foreskin • 60% in US are circumcised • 15% worldwide • Shaft • Glans penis

  9. Penis internal anatomy • Corpus spongiosum • Bulb of penis • Corpora cavernosum • Crura of the penis

  10. Male Duct System • Epididymus • 20 feet! • 20 days for sperm to mature • Smooth muscles expel sperm during ejaculation • Cells have microvilli

  11. Male Duct System • Epididymus • Smooth muscles expel sperm during ejaculation • Cells have microvilli

  12. Male Duct System • Ductus (vas) deferens • 18” • Very muscular • Ampulla

  13. Male Duct System • Vasectomy • Almost 100% effective • Reversal about 50% success rate

  14. Male Duct System • Ejaculatory duct • Urethra • Conveys both urine and semen • Prostatic • Membranous • Penile • Urethral glands secrete mucus prior to ejaculation

  15. Seminal vesicles • Size of little finger • Surrounded by smooth muscle • Seminal fluid • Fructose • Ascorbic acid • Coagulating enzyme • Prostaglandins • Other factors that enhance sperm mobility Glands

  16. Prostate • Size of peach pit • Several ducts into the prostatic urethra • Surrounded by smooth muscle • Secretions • Citrate • Enzymes (fibrinolysin, hyaluronidase, acid phosphatase) • Prostate specific antigen (PSA) • activate sperm Glands

  17. Glands • Bulbourethral glands • Pea sized • Mucus • Lubrication • Neutralizes acidic urine prior to ejaculation

  18. Semen • 2-5ml • Composed of • Sperm (10%) • Testicular fluid • Gland secretions

  19. Semen • Functions • Transport, activation and protective medium • Nutrients for sperm (fructose) • Neutralizes vaginal tract • Prostaglandins reduce viscosity of mucus at cervix • Enzymes enhance motility • Antibiotics • Chemicals that suppress the female immune system • Clotting factors that coagulate semen so it sticks to vagina • Fibrinolysin then dissolves that mass

  20. Physiology • Erection • NO (nitric oxide) released (in penis tissue) • Causes arterioles (normally constricted) to relax/dilate • Blood flows into the corpora cavernosa • Compresses veins to prevent flow out • Corpus spongiosum also expands but maintains open urethra • Bulbourethral glands secrete lubricant

  21. Physiology • Ejaculation • Spinal reflex • Bladder sphincter muscle constricts • Reproductive ducts and glands contract • Contents enter urethra • Muscles around the blub of penis – series of rapid contractions • Other systemic changes • Rapid heartbeat • Elevated blood pressure • Generalized muscle contraction

  22. Erectile dysfunction • Deficient NO release • Viagara, Cialis and Levitra increase effects of NO • Possible factors • Psychological factors • Alcohol or drugs • Antihypertensives, Antidepressants • Diabetes mellitus • Arteriosclerosis • Varicose veins • Nervous system issues • Stroke, Penile nerve damage, MS

  23. Spermatogenesis

  24. Spermatogenesis

  25. Spermatogenesis • Meiosis • Sertoli cells • Nourish and “clean” • Secrete testicular fluid • androgens • Tight junction • Blood-testis barrier • prevents sperm antigens from the immune system

  26. Spermatogenesis • Spermatogenic cell • 64-72 days

  27. Infertility • 1/7 of Americans; most due to sperm issues • Estrogen-like compounds • Antibiotics (tetracycline) • Compounds that lead to abnormal sperm • Radiation, marijuana, lack of selenium, alcohol • Lack of a specific Ca++ channel (for motility) • Anatomical obstruction • Hormonal imbalance • Oxidative stress (damages DNA) • overheating

  28. Hormonal Regulation • Hypothalamic-Pituitary-Gonadal Axis • Hypothalamus • Anterior pituitary • Testes

  29. Hypothalamic-Pituitary-Gonadal Axis • Hypothalamus • GnRH – gonadotropin releasing hormone • Stimulates the anterior pituitary

  30. Hypothalamic-Pituitary-Gonadal Axis • Anterior Pituitary • LH – luteinizing hormone • Released in response to GnRH • Stimulates interstitial cells (Leydig cells) to secrete testosterone

  31. Hypothalamic-Pituitary-Gonadal Axis • Anterior Pituitary • FSH – follicle stimulating hormone • Released in response to GnRH • Stimulates Sertoli cells • ABP – androgen-binding protein: Keeps concentration of testosterone high

  32. Hypothalamic-Pituitary-Gonadal Axis • Testosterone • meiosis of spermatogenic cells • development and maintenance of secondary sex characteristics • Libido • Feed back to pituitary and hypothalamus

  33. Hypothalamic-Pituitary-Gonadal Axis • Inhibin • Secreted by Sertoli cells • produced in response to sperm count • Inhibits release of GnRH and FSH

  34. Hypothalamic-Pituitary-Gonadal Axis • Absence of GnRH, FSH and LH • Testicular atrophy • Accessory organs atrophy • Testosterone production declines (or ceases)

  35. Secondary sex characteristics • Pubic and axillary hair • Facial and chest hair • Larynx enlarges • Skin thickens and becomes oilier • Bones grow and increase density • Skeletal muscle increases • Basal metabolic rate increases • Development of libido • Brain development

  36. Reproductive System Development • 5 weeks • gonadal ridges • Mullerian ducts – female • Wolffian duct – male • Germ cells migrate to gonad

  37. Reproductive System Development • 7 weeks – ductus deferens forms • Seminiferous tubules form in gonadal ridges • Join the Wolffian ducts • Testes secrete MIF – Mullerian Inhibitory factor • Mullerian ducts degenerate

  38. Reproductive System Development • 8 weeks – presence of testosterone • Genital tubercle enlarges • forms penis • Urethral folds fuse • Forms spongy urethra • Labioscrotal swellings fuse • Form scrotum

  39. Reproductive System Development • Gubernaculum (G) (blue) – connects testis to floor of scrotum • At 7 months G stops growing and becomes fibrous • Rapid growth of fetus causes G to pull testis into the scrotum

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