The vas deferens is a narrow, muscular tube that connects the
testicles (where sperm is produced) to the urethra. During ejaculation, the
sperm flows out of the testicles, through the vas deferens, and into the tube
(urethra) that leads outside the body through the penis.
Several glands, such as the prostate gland, add fluid to the sperm
along the way.