auricle

auricle, in the human heart, one of two small ear-shaped muscular projections extending from the atria, one from the left atrium and one from the right. Their primary function is to act as reservoirs, expanding the capacity of the atria and helping regulate blood flow into the ventricles. Structurally, they are characterized by a wrinkled surface formed by the pectinate muscles.

The auricles are clinically important because of their role in certain cardiac disorders. The left auricle (left atrial appendage), for instance, is a frequent site of thrombus (clot) formation in individuals with atrial fibrillation (irregular and rapid beating of the atria), wherein the irregular atrial contractions allow blood to pool and clot within the chamber. These clots can then embolize (break free) and become lodged in smaller vessels in the brain, resulting in ischemic stroke (impairment of brain function because of severe reduction in blood flow). For this reason closure or removal of the left auricle may be performed in patients at high risk of stroke. Auricles are also important in imaging and cardiac surgery, since their size and shape can vary and may influence procedural approaches. Enlargement of the auricles can reflect increased atrial pressure, which is evident in conditions such as mitral valve disease or chronic heart failure.