The bone matrix is the intercellular substance of bone tissue, crucial for its strength and flexibility. It's essentially the framework where bone cells are embedded.
Composition of Bone Matrix
The bone matrix is composed of both organic and inorganic components:
-
Organic Components (Osteoid): Primarily collagen fibers (Type I collagen). These fibers provide flexibility and tensile strength, preventing the bone from being too brittle.
- Collagen: ~90% of the organic matrix.
- Proteoglycans, Glycoproteins, and other proteins: These contribute to bone resilience and act as a binding site for growth factors.
-
Inorganic Components: Primarily mineral salts, mostly calcium phosphate in the form of hydroxyapatite crystals (Ca10(PO4)6(OH)2). These minerals provide the bone with its hardness and rigidity.
- Hydroxyapatite: Makes up about 65-70% of the bone matrix by weight.
- Other minerals: Small amounts of calcium carbonate, magnesium, fluoride, etc.
Function of Bone Matrix
The bone matrix serves several essential functions:
- Provides Strength and Rigidity: The inorganic components, especially hydroxyapatite, give bone its hardness and ability to withstand compressive forces.
- Provides Flexibility: The organic components, especially collagen fibers, give bone some degree of flexibility, allowing it to withstand tension and bending forces.
- Supports Bone Cells: The matrix provides a structural framework in which osteocytes (mature bone cells), osteoblasts (bone-forming cells), and osteoclasts (bone-resorbing cells) reside and function.
- Mineral Reservoir: The matrix serves as a reservoir for calcium and phosphate, which can be released into the bloodstream when needed to maintain mineral homeostasis.
In summary, the bone matrix is a complex composite material that gives bone its unique properties, allowing it to support the body, protect vital organs, and act as a mineral reservoir.
