The circulatory system

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  • The circulatory system
    • veIN = IN to the heart
    • Artery = Away from the heart
    • The heart
      • heart contracts to pump blood around body
        • Has 4 chambers
          • blood flows into the 2 atria via the vena carva (right) & the pulmonary vein (left)
            • the atria contract, pushing blood into the ventricles
              • the ventricles contract = forces blood into pulmonary artery (right) & aorta (left) - out of the heart
                • blood then flows to organs via arteries, returning via veins
                  • the atria fill & process repeats
        • has valves to make sure blood flows in right direction - prevent it flowing backwards
        • walls of heart are mostly made of muscle tissue
      • Double Circulatory system
        • 2 circuits joined together
          • 1st pumps deoxygenated blood to the lungs
            • Oxygen is added
              • The oxygenated blood then goes back to the heart
          • 2nd pumps oxygenated blood around all the other organs of the body
            • the blood gives its oxygen to the body cells
              • the deoxygenated blood returns to the heart to be pumped out to the lungs again
    • The Components of blood
      • Plasma
        • pale straw colour & carries things around the body
          • red blood cells
          • antibodies & antitoxins
          • white blood cells
          • hormones
          • carbon dioxide
            • from the organs to the lungs
          • Urea
            • From the liver to the kidneys
          • Platelets
          • nutrients - e.g. glucose & amino acids
            • the soluble products of digestion - absorbed from gut & taken to cells of the body
      • red blood cells
        • carry oxygen
          • from lungs to all cells in the body
        • doesn't have a nucleus
          • allows more room to carry oxygen
        • Has a bi-concaved shape
          • to give a large surface area for absorbing oxygen
        • contains a red pigment = haemoglobin
      • White blood cells
        • defend against disease
          • Lymphocyte
            • produce antibodies to fight pathogens
          • Phagocyte
            • change shape to engulf pathogens
      • platelets
        • are small fragments of cells
        • have no nucleus
        • Help with bllood clotting
    • Blood vessels
      • Arteries
        • contain thick layers of muscle to make them strong & elastic fibres to let them stretch
        • The walls are thick compared to the lumen
        • pumps blood out at high pressure
      • Capilliaries
        • are v. small
        • arteries branch into capilliaries
        • carry the blood really close to every cell in body to exchange substances with them
          • walls are usually only 1 cell thick
            • increases rate of diffusion - decreases distance it has to diffuse
        • supply food & oxygen and take away waste products e.g CO2
      • Veins
        • have bigger 'lumen' than arteries to help blood flow despite the lower pressure
        • blood is at lower pressure in veins
          • So  walls don't need to be as thick as artery walls
        • have valves to keep blood flowing in right direction

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