[Structure of the right muscle atrioventricular valve in the avian heart]

A morphometrical investigation of the right muscle atrioventricular valve in the hearts of 12 adult pigeons and 16 mature hens has been carried out. Qualitative description and designations of separate parts are given. Basing on the results obtained and on the literature data, a hypothesis is advanced that the special construction of the muscle valve, together with the main morpho-functional purpose--closing of the atrioventricular ostium during ventricular contraction--is used also to increase the internal surface of the right ventricle, increasing dimensions of the free wall (the valve is its part) and correspondingly, its contractile ability.