Male Reproductive System Physiology Overview

Oct 8, 2024

Lecture Notes: Physiology of the Male Reproductive System

Overview

  • Focus on spermatogenesis (sperm production) and hormones regulating male reproductive functions.

Spermatogenesis

Basics of Cell Division

  • Somatic Cell Division (Mitosis):
    • Produces two genetically identical cells.
    • Used for replacing dead/injured cells and tissue growth.
  • Reproductive Cell Division (Meiosis):
    • Produces gametes (sperm and eggs).
    • Reduces chromosome number by half.

Process of Spermatogenesis

  • Takes 65-75 days.
  • Spermatogonia:
    • Stem cells with 46 chromosomes (2n).
    • Some remain as a reservoir for future sperm production.
  • Primary Spermatocytes:
    • Also have 46 chromosomes.
    • Undergo DNA replication before meiosis.
  • Meiosis Stages:
    • First Phase: Formation of secondary spermatocytes each with 23 chromosomes (1n).
    • Second Phase: Formation of spermatids, each with 23 chromosomes.
  • Spermiogenesis:
    • Transformation of spermatids into sperm.
    • Development of acrosome, flagellum, and mitochondria.
    • Sperm released into lumen of seminiferous tubules.

Hormones Regulating Male Reproductive Functions

Hormone Secretion

  • Gonadotropin-Releasing Hormone (GnRH):
    • Secreted by hypothalamus.
    • Stimulates anterior pituitary to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

Hormonal Functions

  • Luteinizing Hormone (LH):
    • Stimulates secretion of testosterone from interstitial cells.
  • Follicle-Stimulating Hormone (FSH):
    • Indirectly stimulates spermatogenesis.
    • Works with testosterone on sustentacular cells to secrete androgen-binding protein.
  • Testosterone:
    • Produced by testes (interstitial cells).
    • Stimulates spermatogenesis, development of male reproductive system, secondary sexual characteristics, and sexual behavior.
  • Androgen-Binding Protein:
    • Keeps testosterone concentration high in blood for spermatogenesis.
  • Inhibin:
    • Released when sufficient spermatogenesis occurs.
    • Inhibits secretion of FSH.

Effects of Testosterone

  • Before birth: Development of male reproductive ducts and testes descent.
  • At puberty: Enlargement of male sex organs and development of masculine characteristics (e.g., muscle growth, voice deepening).
  • Adulthood: Influences sexual behavior and libido.

Summary Table

  • Lists major hormones, site of production, and functions.

Next Lectures

  • Focus will shift to female anatomy and reproductive physiology.