Heart  Morphology   Heart is the contractile organ which enables the blood circulation, and plays an essential part in the setting of its debt and adaptation to physiological variations, and especially to the effort. Heart lining are essentially made of a muscle, the myocard. There are four cardiac cavities; they are separated by pairs by a longitudinal partition which divide our heart in a left hand side (LHS) and a right hand side (RHS) parts. The RHS heart contains blood with a poor oxygen rate, rich in carbonic gas. It ensures the pulmonary circulation. The LHS heart contains blood rich in oxygen; it pulses it in all the tissues, through the arteries. Each side of the heart is composed of an auricle and a ventricle. Auricles receive blood which arrives to the heart through veins. To the right auricle arrive the superior and inferior cave veins; they bring back blood which is poor in oxygen from all the organs but the lungs. In the left auricle come, out of the lungs, four pulmonary veins which carry oxygenized blood. Blood is then directed into the ventricle which empties into a single, wide artery. Out of the RHS ventricle comes the pulmonary artery. It divides into two branches, right and left, which ramify into the corresponding lung. It carries blood which is poorly oxygenized. Out of the LHS ventricle comes the aorta. The atrial-ventricular valves play a double role : On the first hand, they channel the blood out of the auricle towards the ventricle; on the other hand, they prevent, while contraction, or ventricular systole, the ebb flow from the ventricle towards the auricle. One may notice the RHS atrial-ventricular, or triscupid one (left picture) and the LHS atrial-ventricular valve, or mitral one. Each valve is moored to the lining of the corresponding ventricle by fleshy columns, and fibrous ropes. The sigmoid valves of the aorta and the pulmonary artery prevent as well the ebb-flowing of the flood towards the ventricle while its filling, the ventricular diastole.