Summary of osteoblast : bone forming cell of skeletal system

Osteoblast :

It is single nucleated,  large cell  responsible for the synthesis and mineralization of bone during both initial bone formation and later bone remodeling. 

it is differentiated from osteoprogenitor cell. 

Skeletal system contain four types of bone cells.

1.       Osteoprogenitor cells

2.       Osteoblast

3.       Osteocyte

4.       Osteoclast

Functions of osteoblast:

It  is generating new bone matrix .

It synthesis, secrete  and mineralize bone matrix 

It secretes

1.      Type I collagen

2.      Small amount of type V  collagen fibre

3.      Bone matrix protein osteocalcin , osteonectin

4.      Multiadhesive glycoprotein : bone siloproteins 1 and 11, osteoponin and thrombospondin

5.      Various proteoglycans and

6.      Alkaline phosphate 

Features of osteoblast :

·         Size  : 15-30 µm

·         Cuboidal, low columnar or polygonal ,

·         arranged in single layer,

·         eccentrically placed oval single nuclei

·         cytoplasm is basophilic leaving a clear area due to golgi complex,

·         Ultra structurally they have features typical of protein secreting cells

·         Cytoplasm contain abundant rER and free ribosomes 

 

·         Cell membrane of osteoblast has processes which communicate with the adjucent osteoblasts and with osteocytes by gap junctions

·         The osteoblast is differentiate from osteoprogenitor cell

·         As osteoblasts move along the bone matrix, they get stuck in the tissue and turn into osteocyctes.

·         It has ability to divide

·         Osteoblast processes communicate with other osteoblasts and with osteocytes by gap junctions