fourchamber

Fourchamber is a term used to describe a heart with four chambers—two atria and two ventricles. This arrangement creates a separation of oxygen-poor and oxygen-rich blood and supports a double circulatory system that efficiently delivers oxygen to tissues. The term is typically used in anatomy and comparative physiology.

In a four-chamber heart, the right atrium collects deoxygenated blood from the body via the vena cavae, passes it through the tricuspid valve to the right ventricle, which pumps it to the lungs via the pulmonary artery. Oxygenated blood returns to the left atrium through the pulmonary veins, flows through the mitral valve into the left ventricle, and is then pumped to the body through the aorta.

Four-chambered hearts are a characteristic feature of mammals and birds, and are present in crocodilians as well, though crocodilians have a specialized mechanism allowing some shunting of blood between circuits. The four-chamber design supports higher metabolic rates, endothermy, and enhanced aerobic capacity compared with other vertebrates.

During embryonic development, heart chambers form through septation and remodeling of the primitive heart tube, guided by genetic signaling pathways. Congenital defects that disrupt septation or valve formation can lead to four-chamber malformations or mixed blood flow, impacting cardiac function.

See also: Cardiovascular system; Heart; Septum (anatomy).