CS - The Heart

• The circulary system carries food and oxygen to every cell in the body. As well as being a 'delivery service', it's also a 'waste collection service' - it carries waste products to where they can be removed from the body
• The circulatory system is made up of the heart, blood vessels and blood
• Humans have a double circulatory system - two circuits joined together
• In the first circuit of the double circulatory system, the right ventricle pumps deoxygenated blood to the lungs to take in oxygen. The blood then returns to the heart

  
• In the second circuit of the double circulatory system, the left ventricle pumps oxygenated blood around all the other organs of the body. The blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out to the lungs again

  
• The heart contracts to pump blood around the body
• The heart is a pumping organ that keeps the blood flowing around the body. The walls of the heart are mostly made of muscle tissue

  
• The heart has valves to make sure that blood flows in the right direction - they prevent backflow. This is how the heart uses its four chambers to pump blood around

  
• • Blood flows into the two atria from the vena cava and the pulmonary vein
  • The atria contract, pushing the blood into the ventricles
  • The ventricles contract, forcing the blood into the pulmonary artery and the aorta, and out of the heart
  • The blood then flows to the organs through arteries, and returns through veins
  • The atria fill again and the whole cycle starts over

  
• The heart also needs its own supply of oxygenated blood. Arteries called coronary arteries branch off the aorta and surround the heart, making sure that it gets all the oxygenated blood it needs

  
• Your resting heart rate is controlled by a group of cells in the right atrium wall that act as a pacemaker. These cells produce a small electric impulse which spreads to the surrounding muscle cells, causing them to contract

  
• The heart has a pacemaker
• An artificial pacemaker is often used to control heartbeat if the natural pacemaker cells don't work properly (e.g. if a patient has irregular heartbeat). It's a little device that's implanted under the skin and has a wire going to the heart. It produces an electric current to keep the heart beating regularly