What Is the Prostate Gland?
The prostate is a gland located at the base of a man's bladder, behind the pubic bone and in front of the rectum. This gland, which is roughly the size and shape of a small crab apple, weighs only about an ounce in young men. It surrounds the urethra, the tube that carries urine away from the bladder and transports semen during ejaculation.
A good way to envision the prostate is as an apple with the core removed, with the urethra passing through the middle. The prostate's primary function is to produce prostatic fluid, a component of semen. Also, during ejaculation, smooth muscles in the prostate contract to help propel semen through the urethra.
Technically the prostate is not part of the urinary system. But because of its location and relationship to the urethra, the prostate can (and often does) affect urinary function.
Structure of the Prostate
The prostate is made up of three kinds of cells: glandular (epithelial) cells, smooth muscle cells, and stromal cells. The glandular cells produce part of the prostatic fluid. The smooth muscles contract to push prostatic fluid into the urethra during ejaculation. (Smooth muscles are involuntary, which means they are not under the conscious control of the individual.) Stromal cells make up the support structure of the prostate.
The prostate can be divided into three main regions, or zones. Immediately surrounding the urethra is the transition zone. This is the tissue that begins to grow in benign prostatic hyperplasia (BPH). Next is the central zone, which contains a portion of the prostate's glandular tissue. The largest and outermost region is the peripheral zone, the area containing the largest proportion of glandular tissue and the site where most prostate cancers develop. The prostate is encased within a capsule of fiberlike tissue.