UL2.H1.2 +D1 +D2 Bone Cells
Bone Cells:
- Osteogenic cells:
- Undifferentiated precursor cells which are programmed to differentiate into the bone cell lineage
- They proliferate and differentiate into osteoblasts
- These are located adjacent to the external and internal surfaces of bone tissue
- Osteoblasts:
- These differentiate from osteogenic cells and are found on the surface of bone
- They are active cells producing collagen and other proteins for export to form the protein structure of the extracellular matrix of bone
- Which organelle(s) would be abundant in the cytoplasm of these cells?
- Osteocytes:
- These cells are located within lacunae (spaces) in the bone matrix and are responsible for the maintenance of the bone tissue within their immediate locality
- They are connected to each other, and to osteoblasts at the bone surfaces, by cytoplasmic processes lying in channels in the bone matrix
- Osteocytes receive nutrients through these connecting cytoplasmic projections
- Osteoclasts:
- These cells are multinucleate cells which are located on the surface of bone
- They are derived by the fusion of monocytes derived from the bone marrow
- They are responsible for the breakdown of bone matrix
- Bone is continually being broken down and replaced, even after bone growth ceases at age ~ 18 years
The main cell types present in bone are:
Micrograph of Cancellous Bone:
In this micrograph of cancellous bone the main cell types found in bone can be located:
- Osteocytes (1) are found in lacunae and are surrounded by bone matrix
- Osteoblasts (2) are found on the surface of plates of bone
- Osteoclasts (3) are large multinucleate cells which are normally positioned in depressions on the surface of plates of bone
- Osteogenic cells are located on the inner part of the periosteum (4) and are also located within the loose connective tissue surrounding blood vessels located in the spaces between plates of cancellous bone (or at the centre of osteons in compact bone)
- However it is difficult to distinguish osteogenic cells from cells with a fibroblast type morphology
Micrograph of Cancellous Bone
An Osteoclast:
In this micrograph:
- An osteoclast (0) can be seen in a depression in a plate of cancellous bone (B)
- The depression is created as the osteoclast breaks down bone matrix
- The tissue (X) on the left of the micrograph is bone marrow
Micrograph of an Osteoclast
