Читать книгу Musculoskeletal Disorders - Sean Gallagher - Страница 104

Bones serve numerous functions in the human body. Bones provide strength and structural stability to the body and provide a means by which loads can be transferred from one part of the body to another. Biomechanically, they are critical structures in that they provide levers and points of attachment for tendons (driven by muscle contraction) that are essential in permitting movement of the human body. Bones also play an important structural protective role for important organs of the body (most notably as the skull around the brain and the rib cage around the heart and lungs).

However, there is much more to bone than its structural and protective roles. Bones themselves are living dynamic organs and are quite complex in nature. These organs are constantly changing and remodeling to adapt to the stresses imposed them. This attribute permits both restorative and/or adaptive repair and helps to prevent fracture development when damage accumulation is not excessively rapid. Bone remodeling and maintenance is a normal, homeostatic process mediated by chondrocytes, bone‐forming osteoblasts, bone‐resorbing osteoclasts, and the mechanosensing osteocytes. Bone remodeling is triggered by growth, mechanical loading (muscular and/or cyclical), injuries (microcracks or fractures), and various local or systemic cytokines, chemokines, and hormones. During active remodeling, bone matrix is resorbed and replaced where needed in response to the loading demands on the bone. Many studies have demonstrated an anabolic effect of loading on bones in case studies or animal models (Schriefer, Warden, Saxon, Robling, & Turner, 2005; Srinivasan et al., 2003; Warden, Fuchs, Castillo, Nelson, & Turner, 2007; Zhang, Sun, Turner, & Yokota, 2007). Other studies show that depending on the intensity, frequency, and form of loading, persistent intense bone loading can also result in long‐term damage, excessive resorption, and detrimental changes to the cartilage and bone [reviewed in (Barbe & Popoff, 2020)]. This topic will be explored further in Chapter 11.

Bone is also the site of a number of hematopoietic cells and blood cell formation—all essential to the body’s nutrition and protection against infection and damaged tissue. Bones are a major site for the storage of minerals, especially calcium and phosphorus. Lastly, bone plays a critical role in storing nutrients and lipids that serve as an energy reserve for the body.