The prostate is a glandular organ that is normally about 3 cm long (slightly more than 1 inch) and lies at the neck of the bladder and in front of the rectum. The prostate produces a thin, milky fluid that is added to the sperm at the time of ejaculation. It surrounds the urethra, which is a tubular structure that carries sperm and urine out of the penis, therefore prostate diseases often affect urination, ejaculation, and rarely defecation.