The left atrium is one of the four hollow chambers of the heart. It plays the vital role of receiving blood from the lungs via the pulmonary veins and pumping it to the left ventricle.

The left atrium is a small, hollow structure on the superior left side of the heart. It is separated from the right atrium by the interatrial septum and from the left ventricle by the bicuspid (mitral) valve. A thin, irregular pouch of cardiac tissue known as the left auricle extends from the left atrium along its anterior surface. The heart wall of the left atrium is much thinner and weaker than that of the left ventricle. It is made of three distinct layers: the epicardium, myocardium, and endocardium.