Seminiferous tubules of the epididymis (40X)

Closer view of the two different types of tubules The darkest kind of tubule, with very regular form and size of the epithelial cells, is the ductus epididymidis, while the lighter ones with much more irregular epithelial cells,  are the ductuli efferentes. The latter tubules lead the sperms from the rete testis to the ductus epididymidis. On the luminal surface of the ductus epididymidis cells there are many stereocilia, increasing the surface area.  Thin layers of smooth muscle cells surround the tubules.