The prostate gland is a small gland about the size of a chestnut and weighs about 30 grams (about 1 ounce) that is part of the male reproductive system. It is located below the bladder and in front of the rectum, and its most important function is to produce a fluid that mixes with sperm from the testicles and fluids from other glands to form semen. During ejaculation, the muscle cells inside the prostate contract and forcefully press the fluid that has been stored in the prostate out into the urethra, which then combines with sperm cells and fluid from other glands to form semen. The prostate gland is surrounded by a capsule of connective tissue containing many smooth muscle fibers and elastic connective tissue, which is why it feels very elastic to the touch when it is examined. The ducts in the prostate gland flow into the urethra, which passes through the prostate. The prostate gland can be divided into three different zones, which encircle the urethra like layers of an onion: the transition zone, the central zone, and the peripheral zone.

In summary, the prostate gland produces a fluid that mixes with sperm from the testicles and fluids from other glands to form semen, which is then released during ejaculation.