What it is
The prostate is a gland of the male reproductive system. It is located in front of the rectum, just below the bladder, and wraps around the urethra, the tube that carries urine from the bladder out through the tip of the penis. The prostate is made up of 30% muscular tissue, and the rest is glandular tissue. In a healthy man the prostate is nearly the same size and shape as a chestnut. It is common for the prostate to become enlarged as a man ages.

What it does
The prostate gland secretes a slightly alkaline fluid that forms part of the seminal fluid, a fluid that carries sperm during the male orgasm. During the orgasm, the muscular glands of the prostate help to propel the prostate fluid, in addition to sperm that was produced in the testicles, into the urethra. The semen then leaves the body out through the tip of the penis during ejaculation. The prostate fluid in semen helps keeping the sperm healthy and active after ejaculation. A healthy prostate is therefore crucial for human reproduction. The prostate might have more functions, but researchers do not know all of the functions yet.