a-short-review-of-histology

Bone:

Bone is a specialised type of connective tissue
It is composed of cells and extracellular matrix
The main cells present are osteogenic cells, osteoblasts, osteocytes and osteoclasts
These are responsible for the formation, maintenance and breakdown of bone tissue
The extracellular matrix of bone is composed of an organic component (osteoid) which largely consists of collagen fibres
The extensive network of collagen fibres within the bone matrix is mainly responsible for the strength of the bone
The other main component is made up of inorganic salts, particularly calcium phosphate
These give the bone its hardness, essential for providing the solid framework of the skeleton for the attachment of muscles and the support of the soft tissues
However, this inorganic matrix, importantly, also acts as a mineral store
Bone is highly vascular and a good blood supply is essential for the proper growth and maintenance of bones
The internal structure of bones is tightly organised around the vascular network

Electron Micrograph of Bone:

In this electron micrograph of bone:

An osteocyte (0) sits within a space known as a lacuna (L)
This lacuna contains a supportive fluid medium
The lacuna is surrounded by the solid extracellular matrix (ECM) that is characteristic of bone
Notice the cytoplasmic processes (arrows) that project from the body of the osteocyte
Although not shown in this micrograph, these cytoplasmic processes project through small canals in the bone matrix to form junctions with similar processes from adjacent cells
These connections form a network through which nutrients are passed from blood vessels to the osteocytes located in the bone matrix

Electron Micrograph of Bone