Comparative anatomical and histological study on the trachea of native awasi sheep and black goat


To explore the various constituents of the trachea of the local awasi sheep and black goat, gross anatomical, histological and morphometrical studies had been carried out. The study revealed that the average length of the trachea is directly proportional to the number of tracheal rings and it was also noticed that the length, diameter and wall thickness of the trachea of the sheep were greater than those of black goat. These parameters decreased gradually toward the posterior third of the trachea in both species. The free dorsal ends of the tracheal rings of the sheep overlapping each other at the cranial third, but they gradually move a part at the mid – third, and they become again very close to each other and run side to side dorsally to forming a dorsal crest at the caudal third. However, the two free ends of tracheal rings of the goat remain considerably apart throughout the entire length of the trachea forming a (U) shaped configuration. The cartilaginous rings were so oriented that they disposed one beside the other at the ventral and lateral aspects of the tracheal wall. But they overlapping each other at the dorso – lateral aspect of the tracheal wall in both species. Three main cells were detected in the surface epithelium of the trachea of both species (ciliated columnar cells, basal cells and goblet cells), another cell type was restricted to the posterior third of the trachea of both species. The tracheal glands were found to be compound, mixed tubulo – acinar type. The majority of the secretory units were mucous, the others were serous. Most of the tracheal glands occupied the triangular area between the successive tracheal rings particularly at the medial side of the ventral aspect of the trachea. The density of the tracheal glands decreased gradually anterio – coudally in the both studied species. The percentage of goblet cells in the trachea of sheep was greater than that of goat, and decreased gradually toward the lungs in both species.