Comparative Histomorphometric Study of the Common Carotid Artery and Its Terminal Branches in Sheep and Goats

Light microscopic analysis of the mural structure of the common carotid artery (CCA), external carotid artery (ECA) and occipital artery (OA) in Lori Bakhtiari sheep and goats revealed variability in the average values of vascular diameter and the thickness of the intimal plus medial coats and adventitial coat. Based on the histological characteristics and organization of connective tissue fibres and smooth muscle cells in the tunica media, the arterial segments were clearly classified into elastic and muscular types. In both species the common and external carotid arteries were of the elastic type. The number of elastic lamellae in the tunica media of proximal, middle and distal parts of the CCA in both species was 11, 9 and 8 respectively; the number of these lamellae for ECA was 6. The artery distant from the heart gradually decreases its elastic lamellae in the tunica media as well as its elasticity. The OA was of the muscular type. In both species the largest mean value of vascular lumen diameter was determined for the CCA, followed by the ECA. The OA showed the smallest lumen diameter compared to both the CCA and ECA. The conjunct intimal plus medial layers, adventitial layer and lumen diameter were significantly greater in sheep in comparison to goats. The adventitial layer in all vessels were thicker in sheep than in goats but the differences were not statistically significant.