Comparative Valvular Anatomy and Valvulometry of the Pulmonary Valve in Sheep and Goat

Abstract

The pulmonary valve in sheep and goat had three semilunar cusps viz., left, right and posterior that were attached to a ring like annulus at the base of the pulmonary root. Each of the cusp in both species had a hinge, belly and a free margin. The free edge comprised a nodule of Arantius in its middle and lunula on either side. These cusps formed three commissures; left-right, right-posterior and posterior-left placed at the sino-tubular junction.  The mean annular diameter was significantly different between the two species and was 1.3 ± 0.02 cm and 1.4 ± 0.04 cm in sheep and goat respectively. The free edge mean length of left, right and posterior cusps was significantly higher in goat and measured 2.2 ± 0.04 cm, 2.0 ± 0.03 cm and 1.9 ± 0.06 cm respectively. The right-posterior commissural mean height was significantly higher in goat and was 0.8 ± 0.04 cm while the left-right commissural mean height was higher in sheep and was 0.8 ± 0.06cm. The mean depth of these cusps and the mean height of the Posterior-left commissure was without significant difference between species. The cusps in both species were connected by annulus made of densely arranged connective tissue to the ventricular myocardium. All the cusps in both species possessed lamina spongiosa supported by loosely arranged collagen bundles, few elastic and reticular fibers towards the right ventricular side.  Lamina radialis was formed of dense, radial and regularly arranged collagen bundles with few elastic fibers. Lamina fibrosa was seen towards the pulmonary trunk and was formed of dense, regularly arranged collagen bundles, few elastic, reticular fibers and was lined by endothelial cells. The differential mean thickness of left, right and posterior leaflets were insignificant between sheep and goat. Histochemical studies revealed that the histological layers of these cusps showed PAS activity, AB activity, AKP activity and ACP activity at different intensities. No positive reaction for Oil red O and cholesterol was observed in both species.