What are the principal parts of the male reproductive system?
Most of the male sex organs are outside the protection of the pelvic bones. (See Figure 7.2.) The penis, usually soft and flaccid, hangs down in front of the scrotum, or scrotal sac. The scrotum contains two testicles, or testes, the glands that produce sperm and testosterone, the male sex hormone. A long, tightly coiled tube called the epididymis sits on top of and behind each testicle. Sperm are produced in the testicles and are passed into the epididymis, where they mature for several weeks. When the sperm mature, they move into a tube called the vas deferens, which acts as a storage area. During sexual arousal, sperm are collected in the prostate gland and mixed with a fluid generated by the prostate to make semen. Semen is the fluid the male ejaculates through the urethral opening at the tip of the penis when he has an orgasm. Although the urethra is the same tube the male uses for urination, it becomes physically impossible for a man to urinate when he has a full erection. When a
