The prostate gland, a key part of the male reproductive system, is linked closely with the urinary system. It is a small gland that, coupled with the seminal vesicles, secretes the major liquid portion of semen, the milky fluid that transports sperm through the penis during ejaculation.
As pictured in the diagram above, the prostate is located just beneath the bladder, where urine is stored, and in front of the rectum. The urethra, a tubular structure that transports urine from the bladder to the penis during elimination, travels through the prostate organ. During ejaculation, semen is secreted by the prostate through small ducts of the urethra's walls.
The prostate is made up of three lobes encased in an outer covering, or capsule. This capsule is similar to the peal of an apple and separates the prostate tissue from the surrounding fat. The size of the prostate can range anywhere from the size of a chestnut (30 grams) to the size of a grapefruit (>100grams). With increasing age (>50 years) and under the influence of male hormones, the prostate grows in size.
The prostate is flanked on both sides by the seminal vesicles, a pair of pouch-like glands that contribute secretions to the semen. Next to the seminal vesicles run the two vas deferens (the same tubes which are cut during vasectomy); tubes that carry sperm from the testicles for ejaculation. The testicles, in addition to manufacturing sperm, produce testosterone, a male sex hormone that controls the prostate's growth and function.
Male hormones cause the prostate gland to develop in the fetus. The prostate continues to grow as a boy progresses to manhood. If male hormone levels are low, the prostate gland will not grow to full size. In older men, the part of the prostate around the urethra often persists in growing. This causes benign prostatic hyperplasia (BPH), which can result in urination problems — both obstructive and irritative voiding symptoms.