Regional Morphometrical and Histological Studies on the Thoracic Aorta of Buffalo ( Bubalus bubalis )

Abstract

The study reports morphometrical and histological details at different regions of thoracic aorta in buffalos. Specimens of adult, apparently healthy buffalos were collected from local slaughter houses in and around Proddatur. A total of six specimens each were collected three regions viz., immediately behind the origin of common brachiocephalic trunk, at the level of sixth thoracic vertebrae and at the level of hiatus aorticus. The average transverse diameter of the thoracic aorta measured 24.59 ± 0.24 mm, 18.86 ± 0.27 mm and 14.15 ± 0.29 mm, while the average longitudinal diameter of thoracic aorta measured 22.81 ± 0.16 mm, 17.90 ± 0.41 mm and 12.37 ± 0.63 mm in proximal, middle and distal segments respectively. The average transverse luminal diameter of thoracic aorta measured 18.70 ± 0.73 mm, 14.89 ± 0.21 mm and 12.49 ± 0.23 mm, while the average longitudinal diameter of its lumen measured 17.22 ± 0.26 mm, 15.59 ± 0.13 mm and 11.75 ± 0.16 mm in the proximal, middle and distal segments respectively. Average thickness of wall of thoracic aorta measured 5.48 ± 0.17mm, 3.83± 0.13mm and 1.73 ± 0.11mm in proximal, middle and distal segments, respectively. The general histological features of a large artery i.e,, Tunic intima,media and externa were appreciated. Variations were observed in endothelial cell morphology from being elongated to flattened proximally to being rounded in distal segments. Meshwork of connective tissue elements which included branched elastic fibres, collagen fibres and reticular fibres in the subendothelium. An indistinct Internal Elastic Lamina (IEL) observed in the proximal segments of the aorta which became distinct in the distal segment with prominent foldings. Tunica media which constituted the major portion of the thoracic aortic wall was predominantly made up of smooth muscle fibres, elastic lamellae, collagen fibres and reticular fibres in all three segments. Proximal and middle segment of the tunica media revealed smooth muscle fibres which alternated with elastic lamellae in the inner region while the outer region exhibited condensation of smooth muscle fibres into muscle bundles with tapering ends attached to elastic fibres thus forming muscle islands. Indistinct External Elastic Lamina was observed in all the segments. Tunica adventitia was mainly comprised of collagen fibres with fewer elastic and reticular fibres. The predominance of collagen fibres supports the role of the adventitia in providing tensile strength and structural support to withstand hemodynamic forces.The adventitia in all three segments was well supplied with vasa vasorum and nerve fibres.