The prostate gland is a muscular, walnut-sized organ located right in front of the rectum and just below the bladder. The normal prostate gland is approximately 1½ inches long and weighs about an ounce. It completely surrounds the urethra, the tube that takes urine and sexual fluids through the penis and out of the body.
The prostate gland is actually a collection of many smaller glands surrounded by a layer of fibrous tissue called the prostatic capsule. A layer of fat surrounds the capsule. The prostate gland is divided into right and left sides, or lobes. The base is the part of the prostate closest to the bladder; the apex is farthest from the bladder. The front of the prostate is called anterior; the back is posterior.
The prostate gland contains five areas, or zones. The peripheral zone is the largest segment, containing about 75 percent of the glands in the prostate. Most prostate cancer occurs in the peripheral zone and is the site where most needle biopsies are taken. The peripheral zone is also the most common site of chronic prostatitis. The transition zone, the site of benign prostatic hyperplasia (BPH), surrounds the urethra. The anterior zone is mostly smooth muscle and occupies about one-third of the prostate. The central zone holds most of the remaining glands. The muscular preprostatic tissue prevents semen from flowing back into the bladder.
What is the function of the prostate gland?
The main function of the prostate gland is to produce part of the fluid making up semen, the solution that carries sperm.
What is the prostate gland's role in ejaculation?
Semen is produced by both the prostate gland and the seminal vesicles, a pair of glands attached to the prostate. Sperm is produced in the testicles and carried through a tube called the vas deferens to the prostate, where sperm mixes with semen. During orgasm, this fluid is ejaculated first by a connection to the urethra called the ejaculatory ducts and then through the urethra out of the body.
How can the prostate gland affect urination?
Urine is formed in the kidneys, waste-filtering organs located in the mid-back, just below the rib cage. Urine leaves the kidneys and flows down the ureters, two thin tubes that empty into the bladder. When the bladder is full, urine is eliminated through the urethra, which runs from the bladder to the tip of the penis.
The prostate gland sits just below the bladder and completely encircles the urethra at the point where it leaves the bladder. As the prostate enlarges from normal growth or from cancer, it tightens around the urethra and can restrict the flow of urine.