In humans, the prostate is a gland that occurs only in males and is part of the reproductive system. It is roughtly the size of a kiwifruit. It produces a fluid that forms about 20-30% of the volume of semen. This fluid is slightly alkaline and helps the sperm survive longer in the acidic environment of the female vagina. It also contains muscles that assist with ejaculation.
The prostate will not function unless there is sufficient testosterone in the body.