| Components | AF | NP | 
      
        | Water | 60-70    %, no change with age | 90 %    at birth | 
      
        | 80 %    at age 20 | 
      
        | 70 %    at older age | 
      
        | Collagens    (collagen I, collagen II, collagen X-     collagen X is produced by the degenerated disc which has very poor    mechanical properties) | Only    collagen II, 50-60 % with (dry weight) | Only    collagen I, 15-20 % with (dry weight) | 
      
        | Little    change with age | Little    change with age | 
      
        | PGs    (Proteoglycans) | 15-20    % with (dry weight) | 65%    with (dry weight) | 
      
        | Little    change with age | Little    change with age | 
      
        | Non-    collagenous proteins and elastin | 5-25%    with (dry weight) | 20-45%    with (dry weight) | 
      
        | Little    change with age | Little    change with age | 
      
        | Extracellular    enzymes, age pigments, cells | Minor    remainder | Minor    remainder |