The structure of a mammalian heart

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  • The structure of the mammalian heart
    • The heart
      • Muscular double pump.
      • Divided into two sides.
      • The right side pumps deoxygenated blood to the lungs for oxygenation.
      • The left side pumps oxygenated blood to the rest of the body.
      • On both sides, the heart squeezes the blood which puts it under pressure. This pressure forces the blood along the arteries.
    • External features of the heart
      • The ventricles are below the atria.
      • The cornory arteries lie over the surface of the heart. They carry oxygenated blood to the heart itself.
        • Restricted blood flow to the heart muscle reduces the delivery of oxygen and nutrients such as fatty acids.
          • This can cause angina or myocardial infection.
    • Internal features of the heart
      • Deoxygenated blood flows the vena cava into the right atrium.
      • Oxygenated blood from the lungs flows from the pulmonary vein into the left atrium.
      • From the atria, blood flows down through the atrioventricular valves, into the ventricles.
        • Inside the ventricles are tendinous cords.
          • These attach the valves to the walls of the ventricle and prevent the valves from turning inside out which would allow blood to flow up the atria.
    • Blood pressure
      • Atria
        • The muscle is thin. This is because these chambers do not need to create much pressure as the blood is only flowing into the ventricles.
      • Right ventricle
        • They have thick enough walls to ensure blood can be pumped out of the heart.
        • The blood leaves this chamber to go to the lungs.
          • Blood pressure cannot be too much as the capillaries in the lungs are very thin, and they are next to the alveoli, and they could burst.
      • Left ventricle
        • Their walls are two sometimes three times thicker than the right ventricle.
        • The blood from the left ventricle is pumped out through the aorta and needs enough pressure to resist systematic circulation.
      • Muscle of each chamber contracts to create increased pressure in the blood.


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