Notes

Endosteum and periosteum are layers of connective tissue containing osteogenic cells that line the internal and external surfaces of all bones. derived from mesenchymal stem cells . The organic components of bone matrix are produced by osteoblasts. They are only found on the surfaces of bone matrix. Some osteoblasts differentiate into osteocytes after their synthetic activity is finished. some of these cells flatten and cover the matrix surface (bone lining cells) . osteoblasts are actively secreting matrix components. this process is called appositional growth .
Osteocalcin is a vitamin K-dependent polypeptide that, along with other glycoproteins, binds Ca2+ ions and concentrates them matrix vesicles are secreted . hydroxyapatite crystals are formed , and they began to grow bigger as minerals accumulate . osteocytes are differentiated osteoblasts surrounded by the matrix they secret . there found in the lacunae .it has process that occupy the small canals within the matrix , canaliculi .osteocytes communicate with one another and with osteoblasts by gap junctions . it also enable them to act as sensors that detect load or fatigue on bones .they are less developed than osteoblasts
osteoclasts are multinucleated motile cells that play a vital role in matrix remodeling .they are formed by fusing many monocytes together . their development requires two polypeptides which are the macrophage-colony-stimulating factor and the receptor activator of nuclear factor-κB ligand . the sealing zone binds these cells to the bone .
The PERIOSTEUM lines the outer surface of the bone . It has two layers ,the outer one is dense connective tissue containing fibroblasts and periosteal blood vessels delivering nutrients to the bone . the perforating fibers bind the periosteum to the bone. the inner layer contains osteo blasts and stem cells (osteoprogenitor cells )that can produce more new cells .
the ENDOSTEUM . lines the bone marrow and the trabeculae . it also contains stem cells .

or mature bone .Most bone in adults, parallel sheets or concentrically arranged around a central canal. it can be found almost in every bone in the adult body .the osteon is long and cylindrical shaped accumulated lamellae.it contains the blood vessels and nerves in the central canal .
woven bone is newly calcified bones that are irregular arranged .it is replaced by lamellar bone in adults .has low minreal content
intramembranous ossification takes place in flat bones like the skull .ossification centers in the mesenchyme where stem cells proliferate . new osteoblasts secrete osteoid and then centers meet and form woven bone.
in long bones the bulbous end is called the epiphysis and the long shaft is the diaphysis
calcium is very Important as its involved in the permability of membranes , enzyme activity , cytoskeletal movement etc.