ANATOMY

Detailed explanation-1: -The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood out of the heart.

Detailed explanation-2: -The walls of auricles or atria are thin while ventricles are thick.

Detailed explanation-3: -The heart has four chambers (two atria and two ventricles). There is a wall (septum) between the two atria and another wall between the two ventricles. Arteries and veins go into and out of the heart. Arteries carry blood away from the heart and veins carry blood to the heart.

Detailed explanation-4: -The upper chambers-the right and left atria-receive incoming blood. The lower chambers-the right and left ventricles-pump blood out of your heart.

Detailed explanation-5: -While the ventricles are contracting and the atrioventricular valves are closed, blood still continuously flows from the venae cavae on the right, and the pulmonary veins on the left, to fill the atria.