Anatomy of the Heart

The heart consists of three distinct tissue layers. The epicardium is the outermost layer, surrounded by the pericardium, a protective membrane. Beneath it lies the myocardium, composed of cardiac muscle cells forming the heart's walls. The endocardium lines the innermost surface, creating a smooth interior layer.

The right atrium receives blood from the superior and inferior vena cavae, passing it to the right ventricle through the tricuspid valve. The right ventricle then pumps blood through the pulmonary valve into the pulmonary artery. Meanwhile, the left atrium receives blood from the pulmonary veins, sending it to the left ventricle via the mitral valve, which pumps blood through the aortic valve into the aorta.

Heart valves are flaps of connective tissue that ensure blood flows in one direction, preventing backflow. The tricuspid and mitral valves separate the atria from the ventricles, while the pulmonary and aortic semilunar valves prevent blood from flowing backward from the arteries into the ventricles after each heartbeat.

The 'lub' sound results from the closing of atrioventricular valves, which prevent backflow from ventricles to atria. The 'dub' sound is produced by the closing of semilunar valves, which prevent blood from flowing backward from the arteries. When valves fail to close or open completely, this creates an abnormal heart murmur.

The pericardium is a protective membrane that surrounds the heart and keeps it in place within the chest cavity. It creates the pericardial cavity, which separates the pericardium from the epicardium, the outermost heart tissue layer. This structure provides structural support and protection for the heart.

When the heart cannot pump effectively due to blood backflow, ineffective pumping, or decreased blood flow, oxygen delivery to all tissues decreases significantly. This disruption compromises organ and muscle function throughout the body. Cardiovascular disease, the most common cause of death in the United States, results from such heart dysfunction.

Atrioventricular valves, including the tricuspid and mitral valves, separate the atria from the ventricles and prevent backflow into the atria. Semilunar valves, the pulmonary and aortic valves, are located where blood exits the heart into arteries and prevent blood from flowing backward into the ventricles after contraction.