There are different "zones" of the prostate which many patients don't understand. There is a peripheral zone which is the part of the prostate closest to the rectum and really, that's the only part that can be examined by a DRE. The transition zone is generally where enlargement of the gland occurs. There is also an anterior zone which can harbor cancer in the minority of patients.
FUNCTIONS: The prostate serves two main functions: 1) as a male sexual gland producing components of the ejaculate and 2) as a conduit for urine from the bladder to the rest of the urethra. So the obvious question is does one really need the prostate to survive? The answer is no. In fact, in those patients in whom the prostate is removed in a sphincter and nerve-sparing manner, the patient may not even need the prostate to have normal urinary control and sexual function. However, prostate removal does result in sterility.