What is a prostate gland?

The prostate gland acts as the point where semen is mixed and introduced into the urethra where it is ejaculated during orgasm. It is about the size of a walnut and it sits right underneath the bladder. The urethra passes through the center of the prostate and urine flows through it when the bladder is emptied. The ejaculatory ducts from the prostate enter the urethra in the middle of the gland. The purpose of the prostate is to provide chemicals important for sperm to work properly for reproduction. The external sphincter that holds urine in the bladder is below the prostate, so the prostate and bladder have to work together for a man to be continent.