INTERNAL STRUCTURE OF HEART

ON removing the ventral wall the internal structure of the heart becomes clear, the two auricles are separated by septum called tnter-auricular septum ,It pronects to some extent in the ventricle and is so situated that the right auricle is guarded by two thin flap like auriculo -ventricular valves,one arises from the dorsal and the other from the ventral edge of the aperture.these valves are attached to the walls of ventricle by the fine chods of collagen fibres the chordae tendineae.when auricles contract both the valves are flapped backwards and allow the blood to flow into the venteicle .left auricle has opening of the pulmonary veln.The sinas-venosus opens into the right auricle by a transverse aperture called sinu-auricilar aperture having two lip like sinu auricular valves.with the help of these valves blood the auricle but reflux is prevented , the ventricle is thick muscular having severalprojections called columnae carnae.the ventricle into the truncus arteriosus.