Читать книгу Musculoskeletal Disorders - Sean Gallagher - Страница 82

The dry mass of a tendon accounts for about 30% of the total tendon mass, with water making up the remainder (Sharma & Maffulli, 2005). This dry mass portion is 65–80% collagen, 0.2% proteoglycans and inorganic substances, 1–2% elastin, and 4.5% other proteins (O'Brien, 1997). The most abundant type of collagen in tendons is collagen I (95%), with the remaining being collagen III and IV. In immature and healing tendons, collagen III is the initial collagen deposited by tenocytes (and occurs in a disorganized manner) and is subsequently replaced by collagen I. The direction of the collagen fibers is aligned linearly with the stresses exerted on the tendon. Several extracellular proteins cross‐link and act as structural scaffolds for the larger collagen I interdigitating fibrils. These include decorin, fibromodulin, laminin 2, and tenascin C. The inorganic components (calcium and magnesium) are involved in growth, development, and normal metabolism of tendon tissue (Kannus, 2000). There is also an interstitial matrix (Figure 3.13) that contains ground substance, such as mucin (Ali et al., 2015).