Morphological Changes of Intraovarian Arteries in Horses

Abstract

Morphological changes of the arteries in the ovaries of fillies and mares were studied histologically. The major histological features were intimal thickening due to fibromuscular hyperplasia and medial fibroelastotic changes resulting in narrowing of the vascular lumen. These changes in the vascular structure occurred principally in the regressed corpora lutea and cicatric scars of the corpora lutea of both pregnancy and nonpregnancy, and their degree and extent were severer in the small arteries in the vascular colonies left behind by the regressed corpora lutea of pregnancy compared to those of nonpregnancy. Only rarely were changes of the vessels found in the cortical regions except for those in the regressed and cicatrized corpora lutea. These findings suggest that the hemodynamic effects during the presence of a functional corpus luteum may contribute to or be responsible for the vascular lesions in the ovary.