Structure of the heart

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  • Structure of the heart
    • Heart layers
      • The outer layer, known as the pericardium, is a double layered bag surrounding the heart. The fluid between the two layers reduces friction between the heart itself and the surrounding tissue as the heart beats.
      • The second layer is called my myocardium or striped cardiac muscle tissue consisting of united fibres joined by intercalated discs. This muscle tissue is activated by the 'all-or-none law'.
      • The third layer is an inner glistening membrane called the endocardium. Its function is to prevent friction between heart muscle and flowing blood.
    • Heart chambers
      • Two are at the top (atria). Both the right and left atria have thin walls.
      • Two are at the bottom (ventricles). Both ventricles have thicker walls than the atria. The left ventricle wall is the thickest.
      • Since the ventricle pumps blood to the main body mass, whereas the right ventricle pumps blood to the lungs only.
    • Heart valves
      • Heart valves prevent backflow of blood, with the (cuspid) mitral or bicuspid valve sited between the left atria and the left ventricle, and the tricuspid valve sited between the right atria and the right venticle.
      • The semi-lunar valves prevent back-flow of blood into the heart from the pulmonary artery and aorta, and only allow blood to flow in one direction through the heart.
      • This means that when the heart muscles contracts, it only pumps the blood out to the lungs (pulmonary artery) or body (aorta), and not back the wrong way.
    • Blood vessels
      • Blood vessels attached to the heart are the vena cavae and the pulmonary artery on the right side, and the pulmonary vein and the aorta on the left side.


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