taken from Small Gland, Big Problem 4th Edition
by Professor Roger Kirby, Health Press 2011
The prostate gland manufactures an important liquefying component of semen. Sperm are produced in the testicles and then stored just behind the prostate in the seminal vesicles. Here the sperm are in a jelly-like medium. At orgasm and ejaculation, the prostate and seminal vesicles contract, mixing their respective contents. The fluid in the prostate contains large amounts of a substance known as prostate-specific antigen (PSA), which liquefies the gelatinous sperm mixture, allowing the sperm to move freely in search of an ovum to fertilize.