Male Reproductive System

• The testes are outside the body cavity to reach the lower temperature necessary for proper sperm production
• Spermatogenesis is when sperm cell production occurs
• Puberty triggers a hormonal cascade for sperm production similar to females
• Hormonal cascade during puberty

  1. Hypothalamus releases gonadotropin-releasing hormone (GnRH), which tells the anterior pituitary to secrete follicle-stimulating hormone and luteinizing hormone

  2. In females, LH leads to the release of estrogen in the follicles, whereas in males, it spurs the Leydig cells to release testosterone

  3. FSH triggers the sertoli cells to release androgen-binding protein (ABP), which binds to testosterone, creating large local concentrations that trigger sperm production
• Spermatogonia


  • Outermost cells in the tubules, stem cells that initiate sperm-making process by dividing
• Spermatogonia division


  During childhood, spermatogonia continuously divide into two identical daughter cells using mitosis. Testosterone at puberty causes them to divide differently, producing two distinct spermatogonia
• Formation of sperm

  Primary spermatocytes go into meiosis I, form secondary spermatocytes, rush through meiosis II to form four round spermatids with 23 chromosomes each. Spermatids undergo spermiogenesis to grow a tail and become mobile sperm
• Each primary spermatocyte gives rise to four actual sperm
• A mature male can produce 1500 sperm per second
• Movement of sperm

  Myoid cells surrounding seminiferous tubules contract using peristalsis to squeeze sperm and fluid secreted by sertoli cells towards the rete testis in the posterior testis. Sperm then move through the epididymis to gain mobility
• The epididymis consists of the enormous duct of the epididymis, which could be uncoiled to stretch about six meters
• Maturing of sperm in the epididymis

  Sperm work their way through the labyrinth of the epididymis for nearly 20 days, gaining mitochondria for energy to swim hard
• Activation of sperm for movement

  Glandular secretions activate sperm during ejaculation, allowing them to flow through the vas deferens, up behind the bladder, and join with the duct from the seminal gland to create the ejaculatory duct
• Ejaculatory ducts pass into the prostate gland


  Where they empty into the urethra, which runs from the body
• Ejaculation

  Sperm flow from the epididymis through the vas deferens, joins with the duct from the seminal gland to create the ejaculatory duct, passes into the prostate gland, empties into the urethra, which runs from the bladder through the penis and into the outside world
• Ejaculatory ducts pass into the prostate gland


  Where they empty into the urethra
• System of tubes feeding into tubes

  Allows necessary glands to make their contributions to a moving wave of seminal fluid that helps sperm mature and perform their ultimate function -- fertilization
• Components of semen

  • Sperm
  • Testicular fluid
  • Gland secretions
• Semen


  • Provides sperm with transportation, nutritional energy, chemical protection, and activates their motility
• Seminal vesicles

  • Secrete a yellowish, slightly alkaline fluid containing coagulating enzymes, fructose, and other nutrients to help nourish and transport sperm
• Prostate gland


  • During ejaculation, it contracts to squeeze its own special secretion into the urethra, containing mainly citric acid and an enzyme cocktail that helps keep semen liquified
• Bulbo-urethral glands


  • Secrete a clear mucus that drains into the urethra to clear out any acidic urine prior to ejaculation
• Penis


  • Consists of a shaft ending in an enlarged tip called the glans penis, surrounded by a fleshy cuff of foreskin, internally contains three layers of erectile tissues that fill with blood during sexual arousal, resulting in expansion and rigidity for penetration
• The penis is just a delivery system designed to get male gametes as close to female gametes as possible for fertilization