The primary function of the prostate gland is to secrete a fluid which forms part of the seminal fluid that carries sperm. During male orgasm, the muscular glands of the prostate help to propel the fluid, along with sperm from the testicles, through the tip of the penis during ejaculation.
The prostate gland is roughly the size of a walnut. It surrounds the urethra and sits just below the bladder. The prostate is both a muscle and a gland, with ducts opening into the prostatic portion of the urethra. It consists of three lobes with one in the center and one on each side.