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| Normal bone | ||
| Etiology •Not applicable. | ||
| Pathogenesis •Not applicable., | ||
| Epidemiology •Not applicable. | ||
| General Gross Description •The skeleton of the adult human consists of 200-206 distinct bones - 200 skeletal bones and 6 small bones in the middle ear. •There are 26 bones in the spinal column, 8 in the cranium, 14 in the face, 26 in the chest, 64 in the upper extremities and 62 in the lower extremities. •Bones are classified as long bones (mostly in the limbs), short bones, flat bones (mostly in the bones of the skull), irregular or mixed bones (such as the vertebrae and some bones within the skull). •Grossly, bone consists of two portions: compact bone and spongy or cancellous bone. •Compact bone is composed of closely apposed structures known as Haversian systems with relatively little space between them. •Cancellous bone is composed of interlacing fragments of bone, known as spicules or trabeculae, that form a branching interconnected structure. •Between the interconnected branches of the trabecular bone is marrow space. •Bone is composed of 2 kinds of materials, organic and inorganic. •The inorganic component is primarily calcium appatite, a form of calcium phosphate. •The inorganic component is predominantly collagen. •Examples: | ||
| General Microscopic Description •Normal bone is too hard to be cut for histological sectioning. •It therefore has to be demineralized by soaking it in acid solutions to remove the calcium apatite. •What is left behind is demineralized bone matrix, referred to as osteoid. •Osteoid, being composed of collagen, stains pink. •If the bone is improperly or incompletely demineralized, you will find that it stains a bluish color because of the calcium apatite. •Normal healthy living bone contains within it lacunae which contain osteocytes. •Osteocytes are involved in the maintenance of bone and the constant turnover of bone matrix. •Osteocytes communicate with each other and with the surface of the bone through an intricate network of fine channels called canaliculi. •They send fine dendritic processes through these canaliculi to establish communications with neighboring osteocytes. •Another cell involved in the histology of bone is the osteoclast, a cell made from macrophage precursors. •Osteoclasts are involved in the resorption of bone. •They are large, multinucleated cells that are often seen closely apposed to bony fragments and often lie within small semi-circular spaces that represent an area of resorbed bone. •Examples: | ||
| Clinical Correlation •Not applicable | ||
| References Gray H. Gray's Anatomy, 15th Edition. New York: Barnes & Noble, Books, 1995, pp 916 et seq. pp 1 Fawcett DW. Bloom and Fawcett a textbook of histology. 12th ed. New York: Chapman & Hall, 1994, pp Please be patient during transfer. Medline will open in a new window. To return, close the Medline Window Normal bone
| Synopsis by: T.V.Rajan, M.D. Ph.D. (T1X500M00100)[562]
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