MALE REPRODUCTIVE PHYSIOLOGY FOR THE ALLIED HEALTH

THE MALE REPRODUCTIVE SYSTEM

Reproductive Organs

  • Primary Sex Organs: Testes (gonads).

  • Accessory Sex Organs:

    • Seminal Vesicles

    • Prostate Gland

    • Urethra

    • Penis

Functional Anatomy of the Testes

  • Location: Scrotum, sac-like structure, holds two testes.

  • Structure: Ovoid shape, measures about 5 × 3 cm, and weighs approximately 15-19 g.

  • Seminiferous Tubules: 900+ coiled structures in each testis, essential for sperm production.

Scrotum

  • Function: Maintains a temperature below 37°C (98.6°F) for optimal sperm production (35°C is ideal).

  • Temperature Regulation:

    • Dartos Muscles: Contract in cold (scrotum wrinkles), relax in heat (scrotum flaccid).

    • Ensures testicular temperature supports spermatogenesis.

Seminiferous Tubules

  • Weight: Comprise about 90% of testis weight.

  • Spermatogenesis: Sperm is produced here and moves to rete testis for maturation.

Interstitial Cells (Leydig Cells)

  • Function: Secrete testosterone.

Sertoli Cells

  • Role:

    • Nutritional support for spermatids.

    • Forms blood-testis barrier (separates circulatory system and luminal environment).

    • Produces androgen-binding protein and inhibin to suppress FSH levels.

Efferent Ductules

  • Transport sperm from the testis to the epididymis.

  • Blood Supply:

    • Testicular arteries supply blood.

    • Testicular veins drain into inferior vena cava (right) or renal vein (left).

Epididymis

  • Structure: Coiled tube, 2 inches long located on the posterior surface of each testis.

  • Functions: Completes maturation of sperm, storage, and propulsion into ductus deferens via smooth muscle.

Ductus Deferens (Vas Deferens)

  • Extends from epididymis through inguinal canal into abdominal cavity.

Seminal Vesicles

  • Location: Posterior to urinary bladder.

  • Function: Secretes fructose (energy source) and provides alkalinity to enhance sperm motility.

Ejaculatory Ducts

  • Formed where seminal vesicles join ductus deferens; empty into urethra.

Prostate Gland

  • Structure: Surrounds first inch of urethra; weighs about 40 g, opens into prostatic urethra.

  • Secretion: Milky alkaline fluid, aiding sperm motility and providing an optimal environment.

Bulbourethral Glands (Cowper's Glands)

  • Located below prostate, helps to neutralize acidic vaginal environment to aid sperm motility.

Penis

  • Contains erectile tissue and is the external genital organ; glans penis covered by foreskin (prepuce).

Urethra

  • Serves both urinary and reproductive systems, with the meatus at the tip of the glans penis.

Semen

  • Definition: White or gray fluid containing sperm, released during ejaculation.

  • Composition: Secretions from testes, seminal vesicles, prostate, and bulbourethral glands.

  • Properties:

    • Liquid at ejaculation, coagulates, then liquefies again (secondary liquefaction).

    • Alkaline with a pH of 7.5 for optimal sperm function.

Semen Analysis Parameters

  • Volume, pH, liquefaction, sperm count, morphology, motility, pus cells, fructose levels.

Qualities Required for Fertility

  1. Volume ≥ 2 mL

  2. Sperm Count ≥ 20 million/mL

  3. Total Sperm Count ≥ 40 million

  4. 75% alive per ejaculation

  5. 50% motile

  6. Normal morphology > 30%

  7. Defects in head < 35%, midpiece < 20%, tail < 20%.

Disorders Relating to Sperm

  • Azoospermia: No sperm present; congenital or acquired.

  • Oligozoospermia: Low sperm count.

  • Teratozoospermia: Abnormal sperm morphology.

  • Aspermia: Lack of semen due to retrograde ejaculation.

  • Hematospermia: Blood present in sperm due to infection.

Structure of Sperm

  • Total length: 60 μm.

  • Components:

    • Head: Contains nucleus and acrosome (enzymes for fertilization).

    • Neck: Connects head to body.

    • Body: Contains mitochondria.

    • Tail: Main piece propelling movement.

Spermatogenesis

  • Definition: Process of sperm production in seminiferous tubules.

  • Stages:

    1. Spermatocytogenesis

    2. Meiosis (haploid gamete production)

    3. Spermiogenesis (spermatid to spermatozoa).

Role of Temperature in Spermatogenesis

  • Optimal temperature around 32 °C; excessive heat can cause infertility.

Sexual Function and Semen Discharge

  • Erection: Increased blood flow into erectile tissues.

  • Emission and Ejaculation: Movement of semen into urethra and expulsion.

  • Controlled by nervous system; no conscious thought required for erection.

Testosterone Functions

  1. Growth stimulation.

  2. Maintenance of male organs.

  3. Muscle development.

  4. Hair growth stimulation.

  5. Voice changes.

  6. Aggressive behavior promotion.

Disorders Related to Testosterone

  • Hypersecretion can lead to serious conditions; testosterone synthesis defects affect male phenotype, often leading to feminization.

Summary of Key Actions of Testosterone

  • Plays a critical role in male development, reproductive health, and secondary sexual characteristics.