The Male Reproductive System

The Male Reproductive System

• The male reproductive system has one primary function: producing the male genetic code (sperm) and delivering it to the female.
• Spermatogenesis is the production of sperm.
• The anatomy of the male reproductive system and the function of each organ are crucial to understanding this process.

Male Anatomy Terms

• Scrotum: The sac that holds the testes.
• Testes: Male reproductive organs that produce sperm (spermatogenesis).
• Epididymis: A tube (4-5 meters long) where sperm mature.
• Vas deferens: A storage area for sperm (a few hours to 42 days). Fertility isn't affected during storage.
• Seminal vesicle: Secretes an alkaline mucus containing fructose (food for sperm) and prostaglandins (hormone triggering uterine contractions).
• Ejaculatory duct: The area where the vas deferens and seminal vesicles empty during ejaculation.
• Prostate gland: The gland where the ejaculatory duct passes through the urethra; secretes an alkaline mucus to the ejaculate mix.
• Bulbourethral gland (Cowper's gland): Secretes an alkaline secretion to cleanse and lubricate the urethra and penis.
• Urethra: A tube carrying ejaculate out of the body (common to the reproductive and urinary systems).
• Penis: The organ for ejaculate delivery. Composed of two types of erectile tissue: corpus cavernosa and corpus spongiosum. The corpus spongiosum forms the glans penis.

Semen

• Milky-white, viscous fluid ejaculated during sexual activity.
• Contains approximately 120 million sperm/ml and 1-5ml per sexual act.
• The pH is 7.5.
• Contains sperm, secretions from seminal vesicles, prostate gland, and bulbourethral glands.
• Sperm need a pH (6.5-7.5) to be mobile. The alkaline nature of semen neutralises the acidic secretions of the female vagina (pH 3-4).
• Also contains nutrients, acid neutralisers, and agents stimulating uterine contractions.

Seminiferous Tubules

• Located within the testes, these are the sites of sperm formation and initial maturation.

Spermatogenesis

• The testicles (testes) are responsible for producing sperm via spermatogenesis.
• This process begins at ~age 13 and continues throughout a man's life.
• Cells called spermatogonia (singular = spermatogonium), formed during fetal life, begin to pass through stages producing mature sperm cells (spermatozooa).

Stages of Spermatogenesis

• Spermatogonium divides by mitosis to produce a primary spermatocyte and another spermatogonium.
• The primary spermatocyte undergoes meiosis I, reducing its DNA content to form two secondary spermatocytes.
• The secondary spermatocytes undergo meiosis II, leading to four spermatids.
• The spermatids mature into spermatozoa (mature sperm cells).

Meiosis

• Meiosis involves two rounds of cell division (meiosis I and meiosis II) to reduce the number of chromosomes to half of the original diploid state for offspring to have the correct number of chromosomes.
• Critical to spermatogenesis as it produces haploid (1N) gametes (sperm/ova).

Sperm Production and Fertility

• Normal sperm production involves approximately 120 million sperm per ml of semen.
• Fewer than 20 million per ml suggests possible infertility.
• Spermatogenesis takes ~74 days to complete. The ideal temperature is ~3-5°C below normal body temperature. This is why the testes are located outside the body.
• High temperature, excessive alcohol, X-rays, chemotherapy and certain drugs can drastically reduce sperm production.

Circumcision

• A controversial procedure involving the removal of the foreskin of the penis.