the heart

• the circulatory system is made up of the heart, blood vessels and blood
• humans have a double circulatory system
• in the right ventricle, deoxygenated blood is pumped into the lungs to take in oxygen
• in the left ventricle, oxygenated blood is pumped to the organs, where it exchanged its oxygen for carbon dioxide
• the heart contracts to pump blood around the body
• the heart has four chambers: the right atrium , right ventricle , left ventricle and left atrium
• blood flows into the atria from the vena cava and pulmonary vein
• the atria contract, pumping blood into the ventricles
• the ventricles contract, releasing blood into the aorta and pulmonary artery, towards the organs and the lungs
• resting heart rate is controlled by a group of cells in the right atrium which act as a pacemaker
• an artificial pacemaker is often used to control heartbeat if the natural one does not work properly