The Heart
The heart is the major organ of the circulatory system. It is made up of cardiac muscles. Cardiac muscles are only found in the heart. There are four chambers of the heart, the left and right atrium and the left and right ventricle.
Right Atrium- The right atrium receives blood that was brought back to the heart through a vein and then sends it to the right ventricle.
Left Atrium- The left atrium receives oxygen-rich blood from the lungs and sends it to the left ventricle.
Right Ventricle- The right ventricle sends low-oxygen, high-carbon-dioxide blood to the lungs.
Left Ventricle- This part of the heart pumps oxygen-rich blood to the aorta.