Atrium of heart

An atrium of the heart is one of the two thin-walled upper chambers (right atrium and left atrium) that receive blood returning to the heart from the systemic or pulmonary circulation, respectively, and deliver it to the corresponding ventricle.

Each atrium consists of a venous component, an appendage, a vestibule, and is separated from the other atrium by the interatrial septum.

The right atrium receives deoxygenated blood from the body via the superior and inferior vena cava, while the left atrium receives oxygenated blood from the lungs via the pulmonary veins.