THE BASIC STRUCTURE OF BONES - 1
Bones are made of a specialized type of connective tissue formed by resident cells derived from the mesenchyme and by a hard mineralized extracellular matrix.
The bone cells derive from two lineages: an osteoblastic lineage and an osteoclastic lineage, whose cells have specific distributions and exert specialized functions in bones.
The bone extracellular matrix is quite unique, as it is formed by an organic portion and a hard mineralized portion. It has the following main features:
- A predominance of type I collagen fibers in the organic matrix.
- Beside the collagen fibers, the organic portion of the extracellular matrix contains proteoglycans and glycoproteins, some of which are exclusive to or characteristic of bones.
- The inorganic part of matrix is calcified due to the deposition of calcium phosphate on the collagen fibrils forming hydroxyapatite crystals. The teeth extracellular matrix undergoes similar processes.
As collagen fibers stain well with eosin, the bone matrix appears pink following the staining of bone sections with H&E, unlike the cartilaginous matrix that stains bluish/blue by hematoxylin.
Histological sections of bones and teeth
Hard tissues require special methodologies to obtain histological sections. Click on the links to examine them Peparation of hard tissues – bone and teeth – 1 and Peparation of hard tissues – bone and teeth – 2