The terms auricles and atria are often used interchangeably, but they refer to slightly different parts of the heart.
The atria are the two upper chambers of the heart. They receive blood from the veins and pump it into the lower chambers, known as the ventricles. The right atrium receives deoxygenated blood from the body, while the left atrium receives oxygenated blood from the lungs.
On the other hand, the auricles are small, ear-like appendages that extend from the atria. They are also known as atrial appendages. The main function of the auricles is to increase the capacity of the atria, allowing them to hold more blood. This can be particularly important during periods of increased blood flow, such as during exercise.
In summary, the atria are the main upper chambers of the heart responsible for receiving blood, while the auricles are small extensions of the atria that help increase their capacity.