Normal Skeletal Structure and Function
The skeleton consists of two types of bone: compact (cortical) bone and trabecular (cancellous) bone.
Bone undergoes renewal by cellular activities of osteoblasts, osteoclasts, and osteocytes.
Bone is modeled during growth to achieve its final size and density in adulthood.
Bone is remodeled throughout life to provide adequate mechanical support and maintenance of calcium homeostasis.
The principal functions of the skeleton are adequate mechanical support, maintenance of calcium homeostasis and haematopoiesis in the bone marrow.
Bones are extremely dense connective tissues that, in various shapes, comprise the skeleton. Although one of the hardest structures in the body, bone maintains a degree of elasticity due to its structure and composition. Collagen type I fibers are embedded in hydroxyapatite crystals, and both these structures ensure strength and elasticity when loaded. Bone is enclosed, except where it is coated with articular cartilage, in a fibrous outer membrane called the periosteum. Periosteum is composed of two layers — an outer fibrous layer and a deeper elastic layer containing osteoblasts, which are capable of proliferating rapidly when a fracture occurs. In the interior of the long bones is a cylindrical cavity called the medullary cavity, which is filled with bone marrow and lined with a membrane composed of highly vascular tissue called the endosteum.
KeywordsBone Mineral Density Cortical Bone Trabecular Bone Growth Plate Calcium Homeostasis
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