Are auricles extensions of the atria or the ventricles of the heart?

Auricles, or atrial appendages as they are also called, are ear-like structures that are extensions of the atria of the heart. Auricles are muscular pouches, lined with pectinate muscles.

The heart is made up of four chambers. The two upper chambers are the atria and the two lower chambers are the ventricles.

Blood low in oxygen is returned to the heart via veins and is delivered into the right atrium, before being emptied into the right ventricle. From the right ventricle the blood travels via the pulmonary artery to the lungs, where it picks up oxygen.

After the blood has been re-oxygenated, it is returned via the pulmonary veins to the left atrium of the heart. The oxygen-rich blood then passes into the left ventricle and out through the aorta to be pumped around the body, providing it with a fresh supply of oxygen.