The heart’s auricles are small, ear-shaped pouches located on the exterior surface of the atria, the upper chambers of the heart. While the term “auricle” has historically been used to refer to the entire atrium, it more accurately describes these specific appendages.
Where Auricles are Located
There are two auricles in the human heart, each attached to one of the atria. The right auricle, also known as the right atrial appendage (RAA), projects from the upper and front part of the right atrium.
The left auricle, or left atrial appendage (LAA), is similarly positioned on the left atrium. Both auricles are muscular pouches, with the left auricle containing pectinate muscles, which are parallel ridges of muscle. These structures are distinct from the main atrial chambers but are directly connected to them.
How Auricles Function
The primary physiological role of the auricles is to slightly increase the capacity of their respective atria. This allows the atria to hold a bit more blood volume when necessary, acting as small reserve spaces. For instance, when there is increased blood returning to the heart, the auricles can accommodate this extra amount.
Despite their presence, the functional importance of the auricles is relatively minor compared to the main atrial chambers, which are responsible for receiving and pumping blood into the ventricles. The auricles are considered remnants of embryonic development.
Auricles and Heart Health
The auricles, particularly the left atrial appendage (LAA), can have significant clinical implications for heart health. In certain conditions, such as atrial fibrillation (AFib), the LAA becomes a common site for blood clot formation. Atrial fibrillation causes the atria to beat irregularly and rapidly, preventing efficient blood flow and allowing blood to pool in the LAA.
This pooling creates an environment where blood clots can easily form within the LAA’s complex, trabeculated structure. If a clot dislodges from the LAA, it can travel through the bloodstream to the brain, leading to an ischemic stroke. To reduce this risk in AFib patients, medical interventions include the use of anticoagulant medications, which thin the blood to prevent clot formation. Additionally, LAA occlusion procedures, such as surgical removal or device closure, can be performed to seal off or block the appendage, thereby preventing clots from escaping.