Male pelvic anatomy, illustration. At centre is the scrotum, with a testis, the site of sperm production, seen inside it. A section through a testis is at left centre. The grey organ at upper centre is the urinary bladder, which stores urine before it is expelled from the body via the urethra, which runs along centre of the penis (centre to lower left). Below the bladder is the prostate gland (orange), which produces a fluid that forms part of the semen, and sits around the urethra. Below the prostate gland the urethra widens, an area known as the urethral bulb (brown), before entering the penis. From An Improved System of Midwifery, by Wooster Beach (1794-1868), published in 1851.