The prostate gland is a small gland that is part of the male reproductive system. It is located just below the bladder and in front of the rectum. The prostate is about the size of a walnut and surrounds the urethra, which is the tube that empties urine from the bladder. The prostate produces fluid that makes up a part of semen. During ejaculation, the muscle cells inside the prostate contract and forcefully press the fluid that has been stored in the prostate out into the urethra, where it combines with sperm cells and fluid from other glands to form semen.

As a man ages, the prostate tends to increase in size, which can cause the urethra to narrow and decrease urine flow. This is called benign prostatic hyperplasia (BPH), and it is not the same as prostate cancer. Men may also have other prostate changes that are not cancer.

The prostate gland can be divided into three different zones, which encircle the urethra like layers of an onion:

• The transition zone is found on the inside of the prostate and surrounds the urethra. This is the area where most prostate cancers begin.
• The central zone surrounds the transition zone and makes up about 25% of the prostate gland. This zone is responsible for producing the fluid that makes up semen.
• The peripheral zone makes up about 70% of the prostate gland and is located on the outside of the gland. This is the area where most prostate cancers that are not in the transition zone begin.

In summary, the prostate gland is a small gland that produces fluid that makes up a part of semen. It is located just below the bladder and in front of the rectum, and it tends to increase in size as a man ages. The prostate gland can be divided into three different zones, and most prostate cancers begin in the transition zone or the peripheral zone.