Testis, Epididymis & Ductus Deferens The epididymis, ductus deferens, and ejaculatory ducts form the sperm canal. Together they extend from the testis to the urethra, where it lies within the prostate. Spermatozoa are conveyed from the testis along some 20 ductules, or small ducts, which pierce the fibrous capsule to enter the head of the epididymis. The ductules are straight at first but become dilated and then much convoluted to form distinct compartments within the head of the epididymis. They each open into a single duct, the highly convoluted duct of the epididymis, which constitutes the “body” and “tail” of that structure. It is held together by connective tissue but if unravelled would be nearly six metres (20 feet) long. The duct enlarges and becomes thicker walled at the lower end of the tail of the epididymis, where it becomes continuous with the ductus deferens.