The prostate gland is about the size of a walnut. It's located just below the bladder and it surrounds the urethra. This is a tube that carries urine and semen out of the body. The prostate is partly muscular and partly glandular. It has tubes (ducts) that open into the prostatic part of the urethra. It is made up of 3 lobes: a middle lobe, left lobe, and right lobe.
As part of the male reproductive system, the prostate gland’s main job is to secrete a slightly alkaline fluid that forms part of the seminal fluid. This is the fluid that carries sperm. During a man's orgasm, the muscular glands of the prostate help to propel the prostate fluid, and sperm that was made in the testicles, into the urethra. The semen then leaves the body out of the tip of the penis during ejaculation.