THE FINE STRUCTURE OF THE EPITHELIAL LINING OF THE EXCURRENT DUCT SYSTEM OF THE TESTIS OF THE DOMESTIC FOWL (GALLUS DOMESTICUS)
Authors: Tingari M. D. 
Published: December 2014

Ultrastructurally, at least five different cell types were identified in the genital duct system of the cock, namely (1) low cuboidal cells lining the rete testis, (2) and (3) nonciliated type I and ciliated cells, lining the ductuli efferentes and narrow connecting ductules, (4) non‐ciliated type II cells, lining the wide connecting ductules, ductus epididymidis and ductus deferens, and (5) basal cells found mainly with type II cells.

The low cuboidal cells have an imbricated arrangement which, in a tissue section, influences the interpretation of their shape as well as their luminal and basal connections; squamous, cuboidal, and other shapes were observed. They possess a large Golgi complex, many small mitochondria, a few profiles of rough endoplasmic recticulum and electron dense cytoplasmic bodies. The fine structure indicates an active secretory function; the secretion is probably of a protein‐rich type. The cells appear to be capable of taking up spermatozoa from the lumen. There is a rich distribution of nerves in the subepithelial tissue. This could indicate a contractile function of the rete cells; its significance has been discussed.

The non‐ciliated type I cells are characterized by the presence of electron‐dense worm‐like structures which are connected to the surface or scattered in the apical cytoplasm. Their luminal border has many microvilli, some of which form stereocilia. There is an abundance of mitochondria and smooth endoplasmic reticulum; these are evidences of metabolic and secretory activities respectively, but the nature of the secretion is unknown. Lysosomal bodies of many types are scattered throughout the cytoplasm of the non‐ciliated type I cell. The worm‐like bodies may be concerned with the uptake from the lumen.

The main ultrastructural features of the non‐ciliated type II cells are similar to those of protein secreting cells like the exocrine pancreatic acini and salivary glands. There is an abundance of distended rough and transitional endoplasmic reticulum, a well developed Golgi complex, smooth vesicles and electron‐dense secretory granules in various stages of formation. Mature granules are discharged by the fusion of their membranes with the cell membrane of the secretory surface. There is an intimate association between the membranes limiting the endoplasmic reticulum and those of the mitochondria. Dense vacuolated bodies are present in the cytoplasm which are probably lysosomes. The cytoplasmic fibrillar content of these cells and the rich innervation in the subepithelial tissue suggest a contractile function.

The ciliated cells possess a small Golgi complex and many mitochondria, slightly smaller than those of the type I cells and concentrated mainly in the supranuclear region. In view of the presence of motile cilia, and probably the fibrous cytoplasmic bundles, the ciliated cells may function in moving spermatozoa along the excurrent ducts. The cells are non‐secretory but could play a role in the resorption of fluids secreted by the seminiferous tubules in an analogous way to their mammalian counterparts. Electron‐dense, heterogeneous, cytoplasmic bodies occur and are assumed to be lysosomes. Their probable significance pertaining to resorptive functions of the cell has been discussed.

The basal cells have a large dense irregular nucleus and a scanty fibrillar cytoplasm containing few organelles. The nature of these cells in relation to early forms of ciliated cells, precursors of holocrine cells, myoepithelia and transitional forms between myoepithelia and true epithelia has been discussed and a role in ejaculation has been suggested.