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TRANSPORT IN HUMANS (Heart (2 upper chambers: (atria (singular: atrium)…

- - - - Top chambers which receive blood under low pressure from veins.
      - Thin walls as little pressure is required during contraction to push blood into the ventricles
  - - - Bottom chambers of the heart. They receive blood from the atria above.
      - Thicker walls which contract to pump blood out of the heart to areas of the body.
      - The left ventricle has a thicker muscular wall than the right ventricle as it requires more pressure to be created to pump blood to the whole body.
      - The right ventricle wall is thinner as it requires only enough pressure to pump blood to the lungs.
- - - - can become bell-shaped
        
        increases surface area to speed up absorption of oxygen
  - - - 70% water
      - dissolved substances, proteins, hormones
      - contains CO2 (carbon dioxide)
- - - - chest pains
      - heart attacks
      - sudden death
- - - - capillaries->
        
        venules->
        
        veins->
        
        carry blood back to the heart, (main vein= vein cava)
        
        thin walls & less elastic tissue
        
        largest lumen relative to diameter
        
        valves are absent
        
        one-cell thick
        
        large lumen relative to diameter
        
        valves are present