The prostate gland is an organ present only in males. In human beings, it lies just below the bladder, and the urethra (the tube that carries urine) runs directly through it (although in some other mammals, the urethra runs around, rather than through, the prostate). The prostate is part of the male reproduction system and participates in semen production. It is dependent on testosterone and other male hormones. Prostate cancer is a significant form of cancer in older men.