The development of the intratesticular excurrent duct system of donkey (Equus asinus) from birth to maturity

The testis of the donkey was completely descended into the scrotum around birth. It was covered by a thick tunica albuginea consisting of outer and inner fibrous layers in addition to middle vascular one. Discrete bundles of smooth muscle cells were demonstrated in the outer fibrous layer of the tunica albuginea. These cells give the tunica albuginea a contractile function, which may aid in sperm transport. The present study emphasized an irregular arrangement of the testicular lobules of the donkey during various stages of the postnatal life. Such arrangement does not allow some lobules to have direct contact with the mediastinum testis. The latter was located paraxially, toward the epididymal border and extended about two-thirds of the testicular length; it is thick at the head extremity and gradually faded out caudal wards. The connection between the seminiferous cords and the initial part of the straight tubules exhibited a sharp cut contact in neonates, but it demonstrated exfoliated supporting and germ cells, as well as crowded population of peritubular cells in suckling animals. In premature ones, the connection between the seminiferous tubules and straight testicular tubules was characterized by a peculiar structure appearance that attained more modification and development. This connection included two regions; terminal segment of the seminiferous tubule and a dilated initial part of the straight tubule. In mature stage, the terminal segment was composed of three regions with different cellular composition. The duct system of the donkey testis included the intralobular, interlobular, mediastinal and tunical segments in addition to the efferent ductules. From the seminiferous tubules to the efferent ductules, the lining epithelium was essentially the same in cellular composition; however these passages differed in size and configuration from region to another. Correspondence to: Hanan H. abdelhafeez,Assistant professor,Department of anatomy,Embryology and histology.Faculty of veterinary medicine, Assuit, Egypt, E-mail: [email protected]