The prostate is a variable sized gland located in the male pelvis, usually the size of a walnut measuring 3-4 centimeters long by 3-5 centimeters in width. On average, the gland weighs about 20 grams. It is found behind the pubic bone, in front of the rectum, and below the bladder, surrounded by the pelvic muscles. The prostate surrounds the urethra which carries urine from the bladder to the penis and travels in the center of the gland. The seminal vesicles attach to the prostate and produce material that mixes with prostate fluid to form semen. The tubes from the testicles carry sperm to the prostate where the sperm are mixed with the prostate and seminal vesicle fluid. This fluid is then ejaculated during orgasm by a connection to the urethra called the ejaculatory ducts.