An oblong body attached to the upper part of each TESTICLE, composed of convoluted vessels and ducts, which connects the VASA EFFERENTIA to the VAS DEFERENS. Sperm cells produced in the testis pass along the epididymis, maturing as they go, to be stored in the seminal vesicles until EJACULATION occurs. The epididymis may be damaged by trauma or infection resulting sometimes in sterility. Cysts may also occur.