Ask the Doc: What does the prostate do?

Your prostate is about the size of a walnut, and sits below your bladder. The prostate surrounds the urethra; the tube that begins at the base of your bladder and ends at the tip of your penis. The urethra carries urine when you empty your bladder, and semen when you ejaculate.

The main job of the prostate is to produce a fluid that makes up about one third of semen volume. The fluid helps to protect the sperm in the vagina, and contains prostate-specific antigen (PSA), which breaks down the jelly-like consistency of semen after it’s ejaculated into a thinner fluid in which the sperm can move and swim. PSA can be measured in the bloodstream to provide information about prostate health.

Muscles within the prostate tighten during orgasm, releasing semen out through the urethra. Tightening of the top part of the prostate and the bladder muscles during ejaculation directs the semen out through the penis rather than into the bladder (problems with this can result in retrograde ejaculation).

The prostate gets bigger with age and as it does, it can affect your ability to urinate. Eating a healthy diet and doing regular exercise are easy things you can do to keep your prostate healthy and functioning properly.