Scanning Electron Microscopic Studies on the Ventricular Architecture of Pre-natal Non-descript Sheep

Abstract

Background: Heart is the principal organ of circulatory system that pumps blood into the blood vessels and performs many vital functions. Studies on its development before birth of utmost important to safeguard the animal from the occurrence and consequences of various developmental anomalies. The ultrastructural details of ventricular architecture of heart especially in pre-natal sheep has not yet been reported. Methods: The collected foeti of sheep were divided into three age groups viz. early prenatal (up to 50 days), mid prenatal (51-100 days) and late prenatal (101 to 150 days). The samples from ventricles were processed for scanning electron microscopic study and subsequently, the samples were viewed and the photographs were taken in the facility available at Central Instrumentation Facility (CIF), OUAT, Bhubaneswar. The measurements of various parameters of ventricles were also taken at the ultrastructural level. The recorded data were subjected to routine statistical analysis. Result: It was observed that the endocardium of the ventricles consisted of a simple squamous epithelium. The endothelial cells were elongated in shape and arranged linearly on the surface of ventricles in 33 days prenatal non-descript sheep. The boundaries among the endothelial cells were indistinct in this age group. There was presence of pores among the endothelial cells on the surface of the ventricles. In late prenatal period, the endothelial cells of the ventricles became elongated in shape. The subendocardial layer consisted of connective tissue fibers and conducting purkinje fibers, which were quite predominant in the late prenatal period, i.e. at the age of 120 days of gestation. The endocardial fibers were distinctly coiled around the endothelial cells of the ventricles in this age group. The myocardium comprised of cylindrical and highly branched cardiac muscle fibers with pores all over the surface of the myocardium of the ventricles. Each muscle bundle in the myocardium consisted of muscle fibers extending parallel to each other longitudinally and that these fibers made collateral connections with each other in some regions. The papillary muscles were ridge like structures projecting into the lumen of the ventricles of heart. The chordae tendinae connected the papillary muscles and the bicuspid and tricuspid valves. The endothelial surface of the chordae tendinae consisted of elongated endothelial cells with pores among them. The pores of various sizes were arranged linearly in patches on the endothelial surface of the chordae tendinae of the ventricles especially in the late prenatal period, i.e. at about 105 days of gestation.