The rete testis of the goat, a morphological study.

The rete testis of the goat can be divided into three parts, septal, mediastinal and extratesticular. The septal rete is short, relatively straight and connects the terminal part of the seminiferous tubules with the mediastinal rete. The mediastinal rete is a labyrinth of intercommunicating channels that occupies about two-thirds of the central axis of the testis. The extratesticular rete is located outside the testis at its extremitas capitata and forms sac-like dilations up to 2 mm in diameter. The rete testis, regardless of its location, is lined by simple cuboidal to simple squamous epithelium that invariably contains a few intra-epithelial lymphocytes and macrophages. The epithelial cells possess few microvilli and a centrally located flagellum at the luminal border. With the exception of a few small vesicles in the apical cytoplasm, morphological features associated with absorption such as coated vesicles, canaliculi, vacuoles and multivesicular bodies are absent. However, basolateral interdigitations between adjacent cells, another feature of absorptive epithelium, are frequently noticed. Most cytoplasmic organelles except mitochondria and free ribosomes are poorly developed, suggesting that caprine rete epithelial cells are not associated with protein/glycoprotein secretion. There is no evidence of sperm phagocytosis by the rete epithelium, but luminal macrophages containing sperm fragments are occasionally encountered. The structural-functional relationships of the rete epithelial cells are discussed.