section_path: Biological and physiological aspects/Physical anatomy and reproduction/Male anatomy and reproductive system/Internal male anatomy
section_name: Internal male anatomy
paragraph_text: Internal male anatomy
  
  Male internal reproductive structures are the testicles, the duct system, the prostate and seminal vesicles, and the Cowper's gland.
  
  The testicles (male gonads), are where sperm and male hormones are produced. Millions of sperm are produced daily in several hundred seminiferous tubules. Cells called the Leydig cells lie between the tubules; these produce hormones called androgens; these consist of testosterone and inhibin. The testicles are held by the spermatic cord, which is a tubelike structure containing blood vessels, nerves, the vas deferens, and a muscle that helps to raise and lower the testicles in response to temperature changes and sexual arousal, in which the testicles are drawn closer to the body.
  
  Sperm gets transported through a four-part duct system. The first part of this system is the epididymis. The testicles converge to form the seminiferous tubules, coiled tubes at the top and back of each testicle. The second part of the duct system is the vas deferens, a muscular tube that begins at the lower end of the epididymis. The vas deferens passes upward along the side of the testicles to become part of the spermatic cord. The expanded end is the ampulla, which stores sperm before ejaculation. The third part of the duct system is the ejaculatory ducts, which are 1-inch (2.5 cm) -long paired tubes that pass through the prostate gland, where semen is produced. The prostate gland is a solid, chestnut-shaped organ that surrounds the first part of the urethra, which carries urine and semen. Similar to the female G-spot, the prostate provides sexual stimulation and can lead to orgasm through anal sex.
  
  The prostate gland and the seminal vesicles produce seminal fluid that is mixed with sperm to create semen. The prostate gland lies under the bladder and in front of the rectum. It consists of two main zones: the inner zone that produces secretions to keep the lining of the male urethra moist and the outer zone that produces seminal fluids to facilitate the passage of semen. The seminal vesicles secrete fructose for sperm activation and mobilization, prostaglandins to cause uterine contractions that aid movement through the uterus, and bases that help neutralize the acidity of the vagina. The Cowper's glands, or bulbourethral glands, are two pea-sized structures beneath the prostate.