What are the upper chambers of the heart called?

The upper chambers of the heart are called the atria. There are two atria in the heart: the right atrium and the left atrium. These chambers play a crucial role in the heart's function by receiving blood from the body and lungs. The right atrium receives deoxygenated blood from the body through the superior and inferior vena cavae, while the left atrium receives oxygenated blood from the lungs via the pulmonary veins.

Understanding the structure of the heart is fundamental in grasping how blood circulation works, as the atria provide the initial stage of blood flow into the heart, preparing it to be pumped into the ventricles. The ventricles, which are the lower chambers, then propel the blood out of the heart to the lungs and the rest of the body. This distinction underscores the critical role that the atria have within the overall cardiac cycle and circulatory system.