Left atrium
Atrium sinistrum
CardiovascularOrgansThorax
- What it is
- The most posterior chamber of the heart, lying directly in front of the oesophagus. It receives the four pulmonary veins; its narrow, hook-shaped left auricle curls forward along the left side of the pulmonary trunk.
- Function
- Receives oxygenated blood from the lungs and passes it through the mitral valve into the left ventricle.
- Size
- About 4 cm in anteroposterior diameter (upper normal on echocardiography); wall 2–3 mm.
- Clinical note
- In atrial fibrillation blood stagnates in the left atrial appendage, the source of most cardiac emboli that cause stroke; an enlarged left atrium can indent the oesophagus on a barium swallow.