Epididymis: body and tail

The lumen of the duct of the epididymis presents a smooth outline and is lined by a very tall, regular, pseudostratified columnar epithelium with stereocilia. This epithelium decreases in height as the duct progresses from the head to the tail region. 1000x

The lumen of the duct of the epididymis presents a smooth outline and is lined by a very tall, regular, pseudostratified columnar epithelium with stereocilia. This epithelium decreases in height as the duct progresses from the head to the tail region. 1000x

The pseudostratified columnar epithelium is composed of tall columnar cells and rounded basal cells (arrows). The epithelial cells absorb luminal fluid and release glycoproteins into the lumen, which aid in sperm maturation.

Smooth muscle surrounding the epithelium gradually increases in thickness from the head to tail regions. In the head, smooth muscle is circularly arranged (bars), but an outer longitudinal layer is added in the body region and a third layer is added in the tail, characteristic of the muscle layers seen in the ductus deferens.

Spermatozoa entering the epididymis are immature. While stored in the epididymis, spermatozoa accumulate, mature, acquire motility and become capable of fertilizing ova.