Hearts

He hearts are muscular organs that function as the central components of the circulatory system in humans and many other animals. In humans, the heart has four chambers and serves as the primary pump that moves blood through the body.

Anatomy: The heart contains two atria and two ventricles. Valves—the tricuspid, mitral, pulmonary, and aortic—prevent backflow. The heart wall consists of the endocardium, myocardium, and epicardium, and is divided by septa into right and left sides.

Function: Blood flows from the right atrium to the right ventricle and to the lungs for oxygenation, then returns to the left atrium and ventricle to be pumped to the body. The coronary arteries supply the heart muscle with blood. The heart’s pumping action sustains systemic and pulmonary circulation.

Conduction and rate: The heartbeat is initiated by the sinoatrial node and coordinated by the atrioventricular node and other conducting pathways. Autonomic nerves modulate rate and force; normal resting rates range roughly 60 to 100 beats per minute.

Clinical notes: Common conditions include coronary artery disease, heart failure, arrhythmias, and myocardial infarction. Diagnosis uses electrocardiography, echocardiography, stress testing, and imaging modalities to assess structure and function.

Evolution and diversity: Most air-breathing vertebrates have a four-chamber heart, providing complete separation of oxygenated and deoxygenated blood. Fishes have two chambers, while amphibians and many reptiles have three chambers, reflecting different circulatory strategies.

Cultural use: The heart is a widespread symbol of emotion and affection in many cultures, both in art and everyday communication.