The prostate gland lies just under the bladder and surrounds the tube that carries urine from the bladder (the urethra). It produces the fluid in the semen that nourishes sperm. Walnut-sized in young men, the prostate gland enlarges with aging. Three common disorders affect the prostate: benign prostatic hyperplasia, prostate cancer, and prostatitis.

Last full review/revision October 2008 by Gerald L. Andriole, MD