The prostate gland, a key part of the male reproductive system, is linked closely with the urinary system. It is a small gland that secretes much of the liquid portion of semen, the milky fluid that transports sperm through the penis during ejaculation.
The prostate is located just beneath the bladder, where urine is stored, and in front of the rectum. It encircles, like a donut, a section of the urethra. The urethra is the tube that carries urine from the bladder out through the penis. During ejaculation, semen is secreted by the prostate through small pores of the urethra's walls.
The prostate is made up of three lobes encased in an outer covering, or capsule. It is flanked on either side by the seminal vesicles, a pair of pouch-like glands that contribute secretions to the semen. Next to the seminal vesicles run the two vas deferens, tubes that carry sperm from the testicles. The testicles, in addition to manufacturing sperm, produce testosterone, a male sex hormone that controls the prostate's growth and function.