Andrology (1) EN hormones1

Key Male Reproductive Organs

  • Testicles: The testes produce sperm and the hormone testosterone, essential for male reproductive functions.

  • Epididymis: This organ is crucial for the maturation and storage of sperm until ejaculation.

  • Ductus Deferens: This tube connects the epididymis to the urethra, facilitating the transport of sperm.

  • Spermatic Cord: Composed of testicular vessels and ductus deferens, it is surrounded by several tunics, including the parietal vaginal tunic and cremaster muscle, aiding in the regulation of temperature for proper sperm production.

Accessory Genital Glands

  • Seminal Vesicles: Produce fluid contributing to semen, particularly in species such as mice, rats, and rabbits.

  • Prostate Gland: Provides a milky fluid that nourishes sperm and is present across all animals.

  • Bulbourethral (Cowper’s) Gland: Cleans out urine from the penis in species like cats, mice, and rabbits before ejaculation.

Urethra and Penis

  • Urethra: A dual function structure that carries both sperm and urine.

  • Penis: Designed for depositing semen into the female's reproductive tract and excreting urine.

  • Sheath/Prepuse: Protects the penis and maintains proper hygiene.

  • Scrotum: Regulates the temperature of the testes, critical for efficient sperm production as sperm requires lower temperature than the body temperature.

Endocrine Influence on Male Reproduction

Hormonal Control

  • Adrenal Gland: The adrenal cortex releases hormones such as aldosterone (regulating mineral balance), glucocorticoids (modulating glucose metabolism), and androgens (promoting male characteristics).

  • Pituitary Gland: Produces hormones like GnRH, LH, and FSH which are vital for regulating testicular function and sperm production.

    • GnRH: Coordinates the function of the pituitary gland.

    • LH (Luteinizing Hormone): Stimulates testosterone production in the testes.

    • FSH (Follicle-Stimulating Hormone): Essential for sperm production by acting on Sertoli cells.

  • Testosterone: A key hormonal agent that drives prostate growth, sperm production, masculine physical traits, increased muscle growth, and libido.

The Role of Testosterone

Effects on Physiology

  • Sperm Production: Testosterone is crucial for the production and maturation of sperm.

  • Prostate Growth: Testosterone supports the healthy development of the prostate.

  • Erectile Function: It plays a critical role in sustaining erections.

  • Anabolic Properties: Increases muscle mass and bone density and promotes red blood cell production while also influencing hair growth and skin health.

Testosterone Metabolism

Pathways

Testosterone is synthesized through a series of enzymatic steps starting from cholesterol, producing various hormones including progesterone and DHT (dihydrotestosterone), crucial for different physiological responses in males.

Pheromones and Urogenital Systems

Role in Reproductive Behavior

  • Pheromones are chemical signals that affect the behavior of other individuals, particularly in reproduction. Various glands including anal and preputial glands release pheromones that can influence sexual receptivity and mating behaviors in females.

  • The vomeronasal organ (VNO) plays a significant role in detecting these pheromones, which are essential for reproductive synchronization and attracting mates in species like mice and rodents, highlighting the interactions between these chemical signals and sexual behavior.

Specific Pheromones

  • MUPs (Major Urinary Proteins): Secreted in male urine, they are involved in attracting females and promoting estrus synchronization.

  • ESP1: Found in male tear fluids, it can also trigger female sexual receptivity.

  • Various non-volatile and volatile pheromones play different roles in sexual attraction and reproductive timing, indicating the importance of ovarian hormonal status and the ecological context.