The epididymis is a long, coiled tube that stores sperm and transports it from the testes. It appears as a curved structure on the posterior margin of each testis, and is comprised of three sections. These are referred to as the head, body, and tail. Though it bares some superficial resemblance to the testes, the epididymis differs in that it is smaller, and the tubes are larger and less densely packed. At the superior pole of the testis is the head of the epididymis, which stores sperm until it is ready to undergo maturation. Next is the body, a long, twisted tube where the sperm matures, a process which takes approximately one week. Last is the tail, which connects to the deferent duct, also referred to as the ductus deferens or vas deferens. From here, the sperm is transported to the ejaculatory duct. Partially surrounding and separating the epididymis from the testis is a thin sheet of tissue referred to as the tunica vaginalis. The walls of the epididymis are lined in pseudostratified columnar epithelial tissue, meaning that the arrangement of the cells gives the appearance of two layers, although it is only one.
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In Depth: Epididymis