A prostate is a gland found in males that produces a fluid that joins with sperm cells to make semen. It is about the size of a walnut, weighs about .4 ounces on average, and is found before the rectum and beneath the urinary bladder.
The prostate surrounds the urethra that comes from the bladder, which is why many prostate problems are first suspected when a man has trouble urinating.
Medical experts divide the prostate into lobes and zones, including the peripheral, central, transition and anterior fibromuscular zones. Lobes include the anterior lobe, also called the isthmus, the posterior and median lobes, and the lateral lobes.