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
Crisscross heart Crisscross heart Crisscross heart is a type of congenital heart defect where the right atrium is closely associated with the left ventricle in space, and the left atrium is closely associated with the right ventricle. Although it is classified as a defect, the criss-cross is more of a spatial anomaly than a functional one, and it is possible for the heart to have relatively normal functioning. The ventricles are rotated either clockwise or counterclockwise resulting in the twisting of their connection. The actual blood flow stream through the ventricles is not interrupted. In an anatomically correct heart the right atrium