Morphology of the tendinous cords of the atrioventricular heart valves in infants in norm

The objective of the research was to study morphological structure of tendinous cords of the atrioventricular heart valves in infants by means of macroscopic, light optic, histochemical and immunohistochemical methods of examination. Materials for the research were 54 atrioventricular heart valves of infants (from the 28 th day of life to 1 year) died of the reasons not connected with cardio-vascular pathology. Tendinous cords were found to begin from the apices of the papillary muscles and fixed to the cusps of the atrioventricular heart valves to the free ventricular and basal surfaces. During fixation with the valve cusp tendinous cords of infants in their way were branched out into the cords of the first, second or third degrees by means of extended or dichotomic methods. Therefore, more tendinous cords were attached to the valve cusp than are derived from the papillary muscles. The number of tendinous cords is in direct correlation with the number of papillary muscles – the more papillary muscles are, the more tendinous cords are derived from them. The examinations conducted by means of light microscopy demonstrated that the surface of tendinous cords of the mitral and tricuspid valves of infants was covered with the endocardium consisting of the superficial layer of endotheliocytes lying on the basal membrane. Under the endothelium in the structure of tendinous cords of infants the endocardium sudendothelial layer was localized with differentiated bundles of elastic fibers forming a loose plexus. Thick single and chaotically located collagen fibers were localized in the space between thin elastic fibers. Fibrous constituents were surrounded by the amorphous component of the intercellular substance. The base of tendinous cords of the atrioventricular heart valves was composed of the arranged, thick packed, directed straightforward bundles of collagen fibers, and between them there were located immature and mature fibroblasts, fibrocytes being the most numerous group of cells from the fibroblastic range, myofibroblasts and blood. Thereby, tendinous cords of the atrioventricular heart valves of infants belong to the tendinous cords of a fibrous type