Human Heart Photo

The human heart, about fist-sized and nestled in the mediastinum behind the sternum, has a pointed apex at the left fifth intercostal space and base at the second rib, with four chambers visible externally—two atria with auricles and two thicker ventricles separated by grooves marking coronary vessels. The right side handles deoxygenated blood, left oxygenated, with great vessels emerging superiorly—aorta arching left, pulmonary trunk bifurcating, superior vena cava entering right atrium. Pericardial sac encloses it, and surface features like interventricular sulci guide arteries feeding the muscle that beats relentlessly.