What is the prostate and what does it do?

The prostate is a small gland in men approximately the size and shape of a walnut. It sits directly below the bladder, in front of the rectum. The prostate is a part of the male reproductive tract. It produces fluid that combines with sperm to make semen. The prostate surrounds the tube that carries urine from the bladder (urethra). At birth, the prostate gland is tiny. During puberty, the prostate expands evenly. The enlargement that occurs in the second half of life is concentrated in the part of the gland next to the urethra.