THE REPRODUCTIVE SYSTEM: WHAT IS SEMEN ?
The easy answer is that semen is the ejaculate. It consists of sperm plus the secretions from the sex accessory tissues (these include the prostate and seminal vesicles), and is composed of prostaglandins, spermine, fructose, glucose, citric acid, zinc, proteins, and enzymes such as immunoglobulins, proteases, esterases, and phosphatase. Less than i percent of semen comes from other reproductive organs such as the testes and epididymis, which produce sperm.
Semen is not merely sperm; sperm is just a tiny fraction of the seminal fluid. So why the other secretions? In some mammals, sperm removed from the epididymis—having never made contact with secretions from the prostate and seminal vesicles—has proved capable of fertilizing an egg. Many scientists believe the varied secretions that make up semen are there as a buffer, to help sperm survive and remain active, to encourage sperm’s passage in the male and female reproductive tracts, and to minimize environmental shock during intercourse. The presence of sugars such as fructose and glucose may be there to nourish the sperm, to provide energy for sperm’s metabolism on its journey.
And still other secretory products—the zinc, for example, and proteases and immunoglobulins—may exist as disease fighters that cleanse the urethra, repulsing attack by harmful substances in the body that enter the urinary tract.
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