Читать книгу Musculoskeletal Disorders - Sean Gallagher - Страница 96

Bone is a complex and dynamic tissue that continuously undergoes renewal and repair throughout life to fulfill its functions. It bears the weight of the body and provides the framework (i.e., helps the body maintain its shape). The anchoring of muscles to bone also permits mechanical movement and locomotion by providing levers for the muscles (Clarke, 2008). Bone is composed of several cell types and a predominantly collagenous extracellular matrix (the osteoid) that becomes mineralized by the deposition of calcium hydroxyapatite. Bone also hosts hematopoietic cells and provides the environment for hematopoiesis within marrow spaces (which is also the storage site of iron) (Yang, 2010). Its general characteristics are summarized in Table 3.5.

Figure 3.16 Elastic cartilage.

Table 3.5 Summary of Cells, Extracellular Matrix (ECM), Subtypes, and Function of Bone Under Normal Conditions

Characteristic	Description
Tissue type	Dense mineralized connective tissue
Cells	Main cell types: Osteoblasts, bone lining cells, osteocytes, osteoclasts, bone marrow–derived mesenchymal stem cellsAdditional cell types: Hematopoietic cells in marrow spaces
ECM	Collagen type I (~70%), 25% water, inorganic minerals (e.g., calcium, phosphorus)
Subtypes	Cortical bone (compact bone), trabecular (cancellous/spongy bone)
Function	Strength, stability, lever at points of attachment, storage of minerals/lipids/nutrients, blood cell formation