Men have two testicles or testes which are the sexual glands. In the fetus, they develop in the abdomen, but before birth they descend into a fold or pouch of skin known as the SCROTUM. Each testicle consists of up to 1,000 minute tubes lined by cells from which the spermatozoa (see SPERMATOZOON) are formed. Around 4.5 million spermatozoa are produced per gram of testicle per day. These tubes communicate with one another near the centre of the testicle, and are connected by a much coiled tube, the EPIDIDYMIS, with the VAS DEFERENS, which enters the abdomen and passes to the base of the bladder. This duct, after joining a reservoir known as the seminal vesicle, opens, close to the duct from the other side of the body, into the URETHRA where it passes through the PROSTATE GLAND. Owing to the convolutions of these ducts leading from the testicles to the urethra, and their indirect route, the passage from testicle to urethra is over 6 metres (20 feet) in length. In addition to producing spermatozoa, the testicle also forms the hormone TESTOSTERONE which is responsible for the development of male characteristics.