Epididymis: body and tail

The duct of the epididymis is lined by pseudostratified columnar epithelium with stereocilia. Junctional complexes, visible in the apical regions of these cells, provide a tight seal from the luminal contents. As the duct progresses from the head to the tail region, the epithelium decreases in height and the layer of smooth increases in thickness, gaining additional layers from head to tail. 1000x

The duct of the epididymis is lined by pseudostratified columnar epithelium with stereocilia. Junctional complexes, visible in the apical regions of these cells, provide a tight seal from the luminal contents. As the duct progresses from the head to the tail region, the epithelium decreases in height and the layer of smooth increases in thickness, gaining additional layers from head to tail. 1000x

Junctional complexes, composed of zonula occludens, zonula adherens and desmosomes, serve to seal the surface of the epithelium and attach the cells together. By light microscopy, these junctional complexes are often referred to as a terminal bars.

Basal cells are small, round basal cells that rest on the basement membrane and serve as stem cells for the epithelium.

The epithelium also contains a variety migratory immune cells including macrophages, lymphocytes and monocytes. Among these cells are suppressor T cells to prevent the development of an immune response to auto-antigens on spermatozoa.

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

Spermatozoa entering the epididymis are immature. While stored in the epididymis, they mature, acquiring motility and the ability to fertilize an ovum.