the heart

• the heart is a pumping organ that keeps blood flowing around the body, made from muscle tissue
• blood carries oxygen to cells
• the heart has valves to prevent backflow of blood and to prevent the backflow of blood into the left atrium
• the blood flows into the two atria from the vena cava and the pulmonary vein

  
  

  the atria contracts pushing the blood into the ventricles
• the right ventricle pumps deoxygenated blood out through the pulmonary artery to the lungs where it picks up oxygen and returns as oxygenated blood via the pulmonary veins to the left atrium
• the left ventricle pumps oxygenated blood out through the aorta to all other parts of the body
• the heartbeat is controlled by an electrical impulse which starts in the sinoatrial node (SA node)
• the heart rate can increase or decrease depending on how much exercise we are doing
• when exercising more oxygen is needed so the heart needs to beat faster to supply enough oxygen to the muscles
• the heart need its own supply of oxygenated blood to keep working efficiently. coronary arteries supply the heart with oxygenated blood
• coronary arteries branch off from the aorta just above the aortic valve