Evaluation of structural heterogeneity in the heart and arteries of African giant rats ( Cricetomys gambianus , Waterhouse 1840)

Morphological and morphometric features of the heart, aorta and its major branches were investigated in the African giant rat (Cricetomys gambianus). Gross morphometric analysis of the heart revealed that the left ventricle was approximately five times thicker than the right ventricle. Heart weight had a strong positive correlation with body weight, heart length, right ventricular and interventricular septal wall thicknesses. The aortic arch in the C. gambianus branched into three major arteries: brachiocephalic trunk, left common carotid artery and left subclavian artery. The abdominal aorta showed parietal and visceral branches. Histologically, the heart showed three basic layers: inner endocardium, middle myocardium and an outer epicardium. The left ventricular myocardium in C. gambianus had three sub layers: superficial, middle and deep, but the right ventricle lacked the middle layer. The aortic and arterial walls exhibited three tunics: intima, media, and adventitia. Elastic arteries had a series of elastic laminae in the tunica media. The number of lamella units varied among arterial segments, with 28-38 lamellae in the aortic arch. Muscular arteries contained mostly circumferentially arranged smooth muscle cells, while the adventitia in both elastic and muscular arteries consisted of loose connective tissue. Histomorphometric analysis of major branches of the aorta revealed that the renal and common iliac arteries showed tunica adventitia that was comparable in thickness to the tunica media. This study provides foundational morphological and morphometric data on the cardiovascular system of C. gambianus, contributing to the understanding of its morphophysiology.