Anatomy of the Heart

The heart comprises three distinct layers working together for optimal cardiac function. The outermost epicardium protects the heart, the thick muscular myocardium contracts to pump blood, and the innermost endocardium lines the chambers. These layers enable efficient blood circulation and coordinated heart contractions throughout the body.

Deoxygenated blood enters the right atrium from the venae cavae and coronary sinus, then moves to the right ventricle for pumping to the lungs. Oxygenated blood returns via pulmonary veins to the left atrium, flows to the left ventricle, and is pumped throughout the body via the aorta.

Heart valves ensure unidirectional blood flow through the heart chambers and arteries. The atrioventricular valves—tricuspid and mitral—prevent backflow between atria and ventricles during contraction. The semilunar valves—pulmonary and aortic—regulate blood exit from the ventricles into the arteries, maintaining efficient circulation and preventing regurgitation.

The pericardium is a fibrous sac enclosing the heart with two layers: visceral and parietal, separated by a fluid-filled space containing serous fluid. This fluid reduces friction during heart contractions, protecting the heart and allowing smooth movement within the chest cavity during each heartbeat.

The myocardium comprises myocytes arranged in a spiral pattern, enabling efficient blood ejection through coordinated twisting and compression movements. This unique structural arrangement allows the heart to contract effectively and pump blood with maximum force throughout both systemic and pulmonary circulation pathways.

The superior vena cava, inferior vena cava, and coronary sinus deliver deoxygenated blood to the right atrium. The pulmonary artery carries blood from the right ventricle to the lungs for oxygenation, while pulmonary veins return oxygenated blood to the left atrium for distribution throughout the body.

Atrioventricular valves—the tricuspid and mitral valves—separate the atria from the ventricles and prevent backflow during ventricular contraction. Semilunar valves—the pulmonary and aortic valves—are located between ventricles and major arteries, ensuring blood exits the heart in one direction only during systole.