Scanning and transmission electron microscope observations of the terminal segment of the cat seminiferous tubule: epithelial phagocytosis of spermatozoa and latex beads.

The terminal segment of the seminiferous tubule in the testis of the adult domestic cat was investigated using scanning and transmission electron microscopy. The terminal segment gradually tapers towards the tubulus rectus, while transforming into tall columnar supporting cells termed modified Sertoli cells which protrude into the lumen of the tubulus rectus in the form of a plug. There is no distinct central lumen in the plug, rather, it is a narrow slit-like cleft surrounded by the modified Sertoli cells. The modified Sertoli cells of the plug as well as the cuboidal cells lining the tubulus rectus revealed an active phagocytosis of spermatozoa and even injected inert latex beads. These epithelial cells are thought to act as a protective filtration line for foreign bodies including unwanted spermatozoa.