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Uploaded on Aug 3, 2007
The Structure of Bone
This is the structure of bone. Spongy or cancellous bone form the center bulk of all our bones. Its honeycomb structure keeps bone light, in contrast to the heavier, compact bone, which gives it strength. Bone cells or osteocytes are contained in spaces called lacunae. The minute projections of bone cells trail into adjoining channels known as canaliculi. Tissue fluid, which fills the lacunae, allows the transfer of materials between bone cells and capillaries. Haversian systems, each about one-sixtieth of an inch wide, make up the structure of compact bone. Each system is formed by a series of rings called lamellae, which are deposits of mineral salts and collagen fibers. Haversian canals, which run through the center of each Haversian system, contain the blood and lymphatic vessels supplying the bone. Here arteries carrying oxygenated blood are shown in red. Veins carrying deoxygenated blood are shown in blue. The lymphatic vessels are shown in white. A section through the shaft of the femur, a long bone, shows a central mass of spongy bone surrounded by the branching tubular Haversian systems. Blood vessels on the bone surface reach into the center of each Haversian system supplying the bone cells.