The prostate gland is an essential part of the male reproductive system. The prostate gland, as it is commonly called, is not really a gland at all, but an organ that consists of about 70 percent glandular tissue and 30 percent fibromuscular tissue.

In an adult male, it is about the size and shape of a walnut and weighs about 20 grams. It is located directly beneath the male bladder and in front of the rectum. A thick fibrous capsule surrounds the prostate.

In the adult male, the glandular tissue of the prostate secretes a fluid that contributes 20-30 percent of the total volume of the seminal fluid released when a man ejaculates. This prostate fluid is continuously generated by the prostate but increases during sexual excitement.

The combination of spermatozoa, seminal vesicle fluid and prostatic fluid, in addition to a tiny amount of fluid from some minor glands, constitutes semen. The prostate gland fluid is a thin, milky substance that gives semen its characteristic color and odor.

Contents of these secretions include calcium, zinc, citric acid, acid phosphatase, albumin, and prostatic specific antigen. These substances aid in the lubrication of the urethra, and protection, nourishment, and mobility of the sperm in the normally acid environment of the female vagina.

The Size of the Prostate Gland
The prostate grows very little from birth until puberty, but at puberty it undergoes a growth spurt, increasing in weight and doubling its size.

In general, the size of the prostate remains constant for the next 30 or more years. In some men, in fact, the prostate never again increases in size. Unfortunately, however, this is not the case for most men, who will develop some form of nonmalignant enlargement of the prostate, medically known as benign prostatic hyperplasia, or BPH.

According to estimates by the American Foundation for Urologic Disease, more than half of men aged 50 and above have enlarged prostates. This number steadily increases with age, and by age 80 it is estimated that 80 percent of men have prostatic enlargement.