Morphologically , bone can be mature (lamellar ) or immature ( woven ) or unmineralized ( osteoid ) .
2 types of bone in mature skeleton :
. . Compact cortical bone . Consists of 50% Haversian systems (osteons) & 50% interstitial bone . Osteons consist of rings of osteocytes around central canal which carries blood & lymph vessels . The cortical bone surrounds marrow cavities & form shafts of long bones .
. . Cancellous bone . Anastomosing trabeculae within cortical bone and predominantly seen in vertebrae ,flat bones & ends of long bones .
Collagen is triple helix consist of 3 polypeptide alpha chains . Each chain has 1000 amino acids & synthesized within the fibroblasts or osteoblasts and is broken down by collagenases to hydroxyproline & hydroxylysine and excreted in urine .