The prostate is a gland about the size and shape of a walnut. The prostate gland is located in front of the rectum, just below the bladder and it surrounds the urethra. The urethra carries urine from the bladder out through the penis.
The prostate is made up of thousands of tiny fluid-producing glands. Specifically, the prostate is an exocrine gland. Exocrine glands are so-called because they secrete through ducts to the outside of the body (or into a cavity that communicates with the outside). Sweat glands are another example of an exocrine gland.
The fluid that the prostate gland produces forms part of semen, the fluid that carries sperm during orgasm. This fluid, produced in the prostate, is stored with sperm in the seminal vesicles. When the male climaxes, muscular contractions cause the prostate to secrete this fluid into the urethra, where it is expelled from the body through the penis.
In addition to the prostate’s role in producing ejaculate, it also plays a part in controlling the flow of urine. The prostate wraps itself around the urethra as it passes from the bladder to the penis. Muscular fibres in the prostate contract to slow the flow of urine.
As well, the prostate produces a protein called prostate specific antigen (PSA). PSA is released with the ejaculatory fluid and can also be traced in the blood stream. The testing of PSA levels in the blood is used to detect prostate cancer. More information on PSA can be found in the Diagnosis section.