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Light micrograph of a section through a human epididymis, the tube connecting the testis to the vas deferens, in which sperm matures. The epididymis consists of a coiled duct about seven meters long. Its highly coiled shape makes it appear as multiple circles when sliced transversely. The lumen of the duct (white) is lined with pseudostratified epithelium (purple), which is made up of columnar cells with elongated nuclei and rounded basal cells with circular nuclei. The purple fibers extending into the lumen are stereocilia. The duct is surrounded by a layer of smooth muscle. (KEYSTONE/SCIENCE SOURCE/BIOPHOTO ASSOC.)