The male reproductive system is mostly external, or outside the body. Dr. Patel, can you tell us about the organs that make up the male reproductive system?
Sure, Dr. Mayzik. The parts of the male reproductive system located outside of the body, called the genitals, include the penis, scrotum, and testicles.
The testicles are two oval-shaped organs located inside the scrotum, which is the loose sac of skin that hangs behind the penis. The testicles make male hormones, including testosterone, and they produce sperm, the male reproductive cells. The scrotum and testicles are located outside of the body in order to control the temperature of the sperm, which develop normally at a temperature slightly cooler than body temperature.
Sperm cells are stored in a long, coiled tube, called the epididymis, which rests on the backside of each testicle. During sexual arousal, contractions force the sperm from the epididymis into a long, muscular tube called the vas deferens, which then transports the sperm to the urethra in preparation for ejaculation.
The urethra is a hollow tube that carries urine from the bladder through the penis to the outside of the body. The sperm it receives from the vas deferens mixes with fluid from the seminal vesicles and prostate to form semen. Semen travels through the urethra and out of the penis during ejaculation.
Besides the urethra, there are two other tubes in the penis: the two corpora cavernosa. The urethra and corpora cavernosa are wrapped together by a tough, fibrous layer of connective tissue called the tunica albuginea.
The corpora cavernosa are two spongy tubes that are soft until they fill with blood. During sexual arousal, nerve messages release chemicals that increase blood flow into the coropora cavernosa. The smooth muscle in the corpora cavernosa relaxes, which lets blood enter and stay in these tubes. The pressure of the blood makes the penis firm, resulting in erection.