The prostate gland is a walnut-sized structure located in the pelvis. It is sandwiched between the bladder, which is above the gland, and the rectum, which is below. This is why one side of the prostate can be felt during a rectal exam. The prostate surrounds the upper part of the urethra, the tube that runs from the bladder to the tip of the penis for urination. Its primary function is to secrete a fluid that helps to transport sperm.