Blood Vessels 8.2 MindMap

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  • Blood Vessels
    • Elastic Fibres: composed of elastin, can stretch and recoil.
      • Artery walls contain elastic fibres, smooth muscle and collagen.
        • The elastic fibes allow: withstand the force of the blood pumped out of the heart and stretch to take the larger volume of blood.
          • In between the contractions the elastic fibes recoil and return to original length.
            • The recoil helps to even out the surges of blood pumped from the heart to give a continuous flow.
    • Smooth Muscle: contracts or relaxes, which changes the size of the lumen.
      • Arterioles link arteries with capilaries.
        • Arterioles have more smooth muscle and less elastin.
          • Due to: little pulse surge, but can constrict the flow of blood into individual organs.
      • Smooth muscle contracts: this constricts the vessel: this prvents blood flowing into a capillary bed. This is vaso-constriction.
    • Collagen: provides structual support to maintain shape and volume
    • Capillaries
      • Link arterioles with venules.
        • The lumen of the capillary is so small that red blood cells have to travel through in single file.
          • Substances are exchanged through the capillary walls between the tissue cells and the blood.
            • The gaps between the endothelial cells that make up the capillary walls in most ares of the body are relatively large.
              • The gaps are where many substances pass out of the capillaries in to fluid.
                • Ways in which capillaries are adapted to their role:
                  • 1. They provide a very large surface area for the diffusion of substances into and out of the blood.
                    • 2. The total cross section of the capillaries is always greater than the arteriole supplying them, so the rate of blood through capillaries gives more time for exchange of materials by diffusion.
                      • 3. The wealls are a single endothelial cell thick, giving a very thin layer for diffusion.


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