The Heart

Annotations:

• The heart has 4 chambers the right and left atria and right and left ventricles. the atria pump blood into the ventricles. The arteries from the right side is the pulmonary artery which goes to the lungs then into the left atria then left ventricle followed by the aorta rest of the body into the vena cava lastly into the right atria and then right ventricle.

1. Flow diagram
   1. From the rest of the body by vena cava
      1. right atria
         1. right ventricle
            1. pulmonary artery
               1. lungs
                  1. pulmonary vein
                     1. left atria
                        1. left ventricle
                           1. aorta
                              1. rest of the body
   2. The heart has 4 chambers the right and left atria and right and left ventricles. the atria pump blood into the ventricles. The arteries from the right side is the pulmonary artery which goes to the lungs then into the left atria then left ventricle followed by the aorta rest of the body into the vena cava lastly into the right atria and then right ventricle.
2. how it works
   1. The left side of the heart has to pump blood much further so its wall is much thicker.
3. electrical signals
   1. The AV Node starts the pulse by sending an electrical signal around the atria which cause them to contract.
      1. This then reaches the SA node whcih stops the contraction for a very brief amount of time to allow the contraction phase of the atria to finish. It then passes it on.
         1. The Bundle of HIS is next where it is taken down the middle of the septum.
            1. The Purkinje fibres follow taking it to the bottom of the ventricles causing them to contract.
               1. To note the signal does not go through the wall between the AV node and ventricles because that would mean it contracts downwards. This would mean that the way to the aorta is shut off as they are at the top of the heart.