Heart although this description is disputed, as the heart is likely to be slightly larger. Well-trained athletes can have much larger hearts due to the effects of exercise on the heart muscle, similar to the response of skeletal muscle. The heart has four chambers, two upper atria, the receiving chambers, and two lower ventricles, the discharging chambers. The atria open into the ventricles via the atrioventricular valves, present in the atrioventricular septum. This distinction is visible also on the surface of the heart as the coronary sulcus. There is an ear-shaped structure in the upper right atrium called the right atrial
Regional function of the heart heart (also called the myocardial fibers) are arranged in a general circumferential direction in the ventricles. In the LV, the fibers will change gradually in direction from a certain longitudinal-cirumferential direction in the outer layer of the heart (epicardium) to another angulated direction almost orthogonal in the inner wall (endocardium), becoming overwhelmingly circumferential somewhere halfway in the middle of the wall. It is, therefore, perceived that measuring the strain in the circumferential direction is a good indicator of the contractility of the fibers. There are different ways to measure the regional function of the wall. It has been proposed to