heart parts

• Heart


  • Pumps blood through the vessels
  • Has right and left sides
  • Each side has an atrium and a ventricle
• Atria


  Have thin muscular walls and receive blood under low pressure returning to the heart in veins
• Ventricles


  Have thick muscular walls and pump blood at high pressure into arteries
• Right atrium


  Receives deoxygenated blood from the body (except the lungs) via the vena cava
• Right ventricle


  Pumps deoxygenated blood into the pulmonary artery leading to the lungs
• Left atrium


  Receives oxygenated blood from the lungs via the pulmonary vein
• Left ventricle


  Pumps oxygenated blood into the aorta leading to the body
• The left ventricle has a much thicker wall than the right ventricle, because it pumps blood a greater distance than the right ventricle which only supplies blood to the lungs
• Blood flows in one direction through the heart and blood vessels
• Atrioventricular valves


  Open to allow blood into the ventricles, close as the ventricles contract to prevent backflow of blood into the atria
• Tendinous cords


  Prevent the atrioventricular valves turning inside out as the ventricular pressure increases
• Semilunar valves


  Open to allow blood into the pulmonary artery and aorta as the ventricles contract, close as the ventricles relax to prevent backflow of blood into the ventricles
• what happens in the cardiac cycle(pressure)?

  1. Blood from vein/body flow into atrium, pressure increases
  2. bicuspid valve opens, blood flows into ventricle
  3. ventricle contracts, pressure in atrium decreases, pressure in ventricles increases
  4. bicuspid valve closes
  5. semilunar valve opens
  6. blood flows into artery/aorta, pressure in aorta/artery increases, pressure in ventricle decreases
  7. ventricles relax, semilunar valve closes
• Myogenic heartbeat

  Beats with its own rhythm, the muscular contractions of the heart originate from within the heart muscle itself
• Sinoatrial node (SAN)


  • A patch of modified muscle cells in the wall of the right atrium
  • Produces regular bursts of electrical impulses, known as waves of depolarisation across the atria, causing them to contract together
• Control of heartbeat

  1. impulses reach the atrioventricular node (AVN) between the atria and ventricles

  2. There is a delay of 0.15 seconds before the AV node reacts

  3. This ensures that the ventricles contract after the atria allowing time for them to fill with blood

  4. Impulses from the AV node travel rapidly through Purkyne fibres (modified cardiac cells) organised into the Bundle of His, to all parts of the ventricles

  5. The ventricles are stimulated to contract together, starting at the bottom, to push the blood up and out into the arteries