Full Male Reproductive Organs (Midsaggital Cross-section View) Description
[Continued from above] . . .
The external organs of the male reproductive system include the penis and scrotum. The penis is a skin-covered erectile organ located in the pubic region inferior to the umbilicus. It surrounds the urethra and provides an outlet for urine and semen to exit the body. Erectile tissue in the penis fills with blood during sexual arousal, causing the penis to enlarge and harden. This phenomenon allows the penis to penetrate into the vagina during sexual intercourse to deliver sperm into the female reproductive tract. Inferior to the penis is the scrotum, a sac of hair-covered skin and muscle that houses the testes. The muscles of the scrotum maintain the correct temperature for spermatogenesis by contracting to lift the testes closer to the body for warmth or relaxing to let them cool if they become too hot.
Inside the protective sac of the scrotum lie the testes, a pair of oblong glands that produce sperm, the male gamete, and the hormone testosterone. The testes produce billions of sperm cells throughout a lifetime from stem cells in their inner walls. Maturing sperm pass through tiny tubules in the testes before entering the epididymis, a crescent-shaped organ that sits on the back of the testes. The epididymis contains many convoluted tubules that play a vital role in the support and maturation of sperm cells. By the time sperm exits the epididymis and enters the ductus deferens, it is ready to swim through the female reproductive tract and fertilize an ovum.
The ductus deferens carries sperm out of the scrotum and into the abdominopelvic cavity where it reaches the prostate. The prostate is a dense gland at the base of the urinary bladder. Roughly the size of a golf ball, it surrounds the urethra as the urethra exits the bladder. Along with the seminal vesicles, the ductus deferens from each testis meet at the prostate to form the ejaculatory duct. During ejaculation, sperm from the ductus deferens is mixed with the liquids produced by the prostate and seminal vesicles to form semen, which is then pushed by smooth muscle contraction into the urethra.
The urethra is a muscular tube that carries both urine from the urinary bladder and semen from the reproductive tract out of the body through the penis. Smooth muscle in the lining of the urethra helps to propel semen out of the body during ejaculation by contracting in powerful waves known as peristalsis. The urethra exits the body at the tip of the penis, which helps to deliver semen into the female reproductive tract to encourage fertilization.
Prepared by Tim Taylor, Anatomy and Physiology Instructor