Histomorphologic studies of the nasal cavity of sheep (Ovis aries) and its significance in temperature regulation of the brain.

10 sheep were used for light microscopic studies to described the distributions of the blood vessels, epithelium, and glands of the nasal cavity. The animals were killed following intramuscular injection of Rompun solution (xylazine hydrochloride). The heads were sawed and tissues were taken from the alar fold, respiratory, and olfactory regions. More vascularity was noticed in areas of the nasal cavity that were in direct contact with the airstream. Moreover, in the submucosa, the presence of arteriovenous anastomoses, collagen fibers, elastic fibers, thick-walked or cushion veins, and free smooth muscle cells were observed, gradually decreasing from the rostral to caudal regions. The tunica media of the arteries was very thin in the vestibular region and relatively thicker in the respiratory region. On the other hand, luminal diameters of the arteries were very small in the respiratory region and relatively larger in the vestibular region. In addition, a large number of intraarterial bolsters was present in the respiratory region, but there were fewer in the olfactory region, and they occurred with still less frequency in the vestibular region.