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TRANSPORT IN HUMANS (heart (four chambers of heart are: (right atria…

- - - - microscopic vessels with a wall only one-cell thick.
    - - the blood pressure in the veins is lower due to the veins being unable to withstand the high pressure blood pumped out of the heart.
      - backflow of blood is prevented by the semi lunar valves. blood moving backwards causes the valves to close.
      - carries deoxygenated blood with the exception of the pulmonary veins.
      - carries blood back to the heart with the exceptions of the portal veins which carry blood between 2 capillary beds, eg: hepatic portal vein.
    - - blood vessels that carry blood away from the heart
      - thick, muscular and elastic walls that can withstand the surge of the high pressure blood pumped out of the heart
      - carries oxygenated blood (except the pulmonary arteries
      - is splitted up into arterioles which are structurally similar to arteries but smaller in diameter.
- - - - membrane-bound fragments of cytoplasm from the bone marrow
        
        plays a part in blood-clotting
    - - red blood cell (erythrocytes)
        
        contains haemoglobin
        
        biconcaved shape
        
        nucleus is absent
      - trasnposrts
        
        oxyhaemoglobin (unstable)
        
        CO2 bound to haemoglobin
    - - colourless (no haemoglobin)
        
        mobile
        
        irregular in shape
      - phagocytes
        
        carries out phagocytosis; the ingestion of foreign particles
        
        lobed nucleus
        
        granular cytoplasm
      - lymphocytes
        
        produces antibodies to protect the body against micro-organisms
        
        small amount of non-granular cytoplasm
        
        large rounded nucleus
    - - soluble proteins are distributed here
        
        90% water
        
        has insulin & other
      - transports
        
        simple sugars, amino acids, fatty acids and glycerol from capillaries to small intestine.
        
        waste products of metabolism
        
        CO2 in the form of hydrogen carbonate ions
        
        nitrogenous waste products like urea, uric acid and creatinine to kidneys to be removed.
        
        hormones
        
        heat from muscles and liver throughout the body
- - - - blood enters the heart through the two atria and exits through the two ventricles.
      - deoxygenated blood enters the right atrium through the inferior and superior vena cava
    - - act as a holding chamber for blood returning from the lungs and to act as a pump to transport blood to other areas of the heart.
    - - have thinner walls than left ventricle
    - - has thicker muscular walls than right ventricle to be able to pump blood to the rest of the body