The epididymis (from the Greek, meaning “upon the twin,” with twin being the testis) is a long, twisted and coiled tubule. It occupies a space of about 1.5 inches (4 centimeters), but if uncoiled it would measure 20 to 23 feet (6 to 7 meters) long. While in the epididymis, sperm mature and gain motility. The epididymis stores sperm until they are ready to be ejaculated. The smooth muscle of the epididymis helps propel mature sperm into the ductus deferens via peristaltic contractions.