Anatomy of the Heart: Structure and Function

Anatomy of the Heart

Structure

The heart is a four-chambered muscular organ that serves as a pump to circulate blood throughout the body. It is located between the lungs in the middle of the chest, slightly to the left of center. The heart is shaped and sized roughly like a man's closed fist and weighs between 7 and 15 ounces. It is enclosed in a pericardial sac that is lined with the parietal layers of a serous membrane.

The heart wall consists of three layers: the outer layer, the epicardium; the middle layer, the myocardium; and the inner layer, the endocardium. The myocardium, the thickest layer, is composed of cardiac muscle fibers which contract to pump blood through the heart. The inner layer, the endocardium, lines the chambers and is continuous with the blood vessels.

The heart is divided into four chambers: two upper chambers called the right atrium and left atrium, and two lower chambers called the right ventricle and left ventricle. The right atrium receives non-oxygenated blood from the body's largest veins, the superior and inferior vena cava, and pumps it through the tricuspid valve to the right ventricle. The right ventricle pumps the blood through the pulmonary valve to the lungs, where it becomes oxygenated. The left atrium receives oxygenated blood from the lungs and pumps it through the mitral valve to the left ventricle. The left ventricle, the largest and strongest chamber, pumps the oxygen-rich blood through the aortic valve to the rest of the body.

The heart also contains the sinoatrial node, the heart's natural pacemaker, located in the right atrium. It initiates electrical impulses that stimulate the heart to contract, regulating the heartbeat. The heart muscle contracts and relaxes in a coordinated manner to pump blood effectively throughout the body.

In summary, the heart is a four-chambered organ enclosed in a pericardial sac with three layers of tissue. The heart is responsible for pumping blood throughout the body, with each chamber playing a specific role in the circulation process. The heart muscle contracts and relaxes in a coordinated manner, regulated by the sinoatrial node.

Learn about the structure of the heart, including its chambers, layers, and functions. Explore how the heart acts as a pump to circulate blood throughout the body and the role of each chamber in the circulation process.