THE PROSTATE: ANATOMIC VIEW
Anatomically, the prostate is divided into five zones: anterior, which occupies 30 percent of the space and consists mainly of smooth muscle; peripheral, the largest segment, which contains three-fourths of the glands in the prostate; central, which holds most of the remaining glands; preprostatic tissue, which plays a key role during ejaculation (muscles here prevent semen from flowing back into the bladder); and transition, which surrounds the urethra and is the sole site of benign prostatic hyperplasia (BPH). Most prostate cancer occurs in the peripheral zone. Also, this is the region most likely to be tapped in a needle biopsy of the prostate.
The prostate is not the sole basis for a man’s fertility or potency. Some animals that have had their prostate (or, in fact, their seminal vesicles—but not both) removed remain fertile. But growth of the prostate clearly is linked to sexual development: Starting at puberty, the prostate enlarges five times in size— from a weight of about 4 grams to 20 grams—by about age 20. For the next several decades, prostatitis is the most common form of prostate trouble; then, after about age 50, BPH and prostate cancer take over as the problems to worry about.
Most animals have a prostate. But only humans and dogs are prone to prostate trouble, and nobody knows why. What makes bulls, for instance, immune to prostate cancer? Why don’t cats get BPH? Again, a mystery.
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