1.2.1 Structure And Function Of Bones

Front 1

Structure, matrix, inorganic

Back 1

3Ca3(PO4)2 + Ca(OH)2 = Ca10(PO4)6(OH)2
Calcium phosphate combines with calcium hydroxide to make hydroxyapatite.
This exists in needle like crystals between collagen fibres

Front 2

Structure, matrix, organic

Back 2

Collagenous fibres form a framework for the hydroxyapatite crystals.
Ground substance supports, adheres and takes part in metabolic functions.

Front 3

Origins of cellular component

Back 3

Primitive mesenchymal stem cell > osteoprogenitor cell > osteoblasts and osteocytes
Monocyte/macrophage line > osteoclasts

Front 4

Osteoblasts

Back 4

- Present on bone surfaces and lining internal cavities
- Secrete the proteins and organic contents of the bone matrix
- Important in calcifying bone - elevate local concentration of calcium phosphate above solubility level, triggering deposition
- Specific receptors for PTH and calcitol
- When inactivated, some will be incorporated into new bone as osteocytes.

Front 5

Osteocytes

Back 5

Mature bone cells that become trapped in the matrix they have secreted.
- linked with adjacent osteocytes by fine cytoplasmic processes through canaliculi
- this allows exchange of Ca2+ from interior to exterior to ECF
- maintain the surrounding protein and mineral content by breaking down and building up surrounding matrix

Front 6

Osteoclasts

Back 6

Giant multinucleate cells, contributing to bone remodelling by resorption.
- have a role in long-term Ca2+ maintenance by their response to PTH and calcitonin.

Front 7

Microscopic structure: compact

Back 7

- Many cylindrical osteons, each with a central canal, allowing nutriet exchange between trapped bone cells
- Lacunae are small spaces in the matrix which contain tissue fluids and trapped bone cells
- Concentric lamellae are cylinder shaped layers of calcified matrix between osteons. They are remnants of older osteons.
- The central canal is lined with endosteum, and contains blood and lympahtic vessels and nerves.
- Canaliculi radiate out from the lacunae and interconnect osteons and the central canal.

Front 8

Microscopic structure: cancellous

Back 8

- Needlelike bony branches called trabeculae
- Branches are fractal and arranged along lines of stress
- Nutrient exchange occurs by diffusion from the canaliculi.