Bone TissueChapter 6Histology of Bone Tissue:Keeping in mind that bone is a connective tissuethere are several cell types that comprise it. The matrix which supports these cells is rich in fibers such as collagen and inorganic compounds such as hydroxyapatite, a type of calcium based salt,which helps give the tissue its’ strength and form.Bone CellsMajor Cell Types:1.Osteoprogenitor Cells(Osteogenic)- stem cellswhich have committed to the bone lineage. Found in the endosteum, inner surface of the periosteum and blood vessel canals in the bone. These cells will give rise to bone forming cells called osteoblasts2.Osteoblast- formed from osteogenic cells, these are the bone formers. They are responsible for producing the boney matrix (hence they are the fibroblast of bone tissue). Once an osteoblast has surrounded itself in boney matrix it matures into an osteocyte3.Osteocyte- mature bone cell; resides in little spaces (air pockets in the boney matrix) called lacunae. Lacunae areinterconnected by thin channels termed canaliculi. .4.Osteoclast- bone degrader; responsible for bone resorption/breakdownMatrix Composition:Organic components- collagen and protein-carbohydrate complexes Inorganic components- Hydorxyapatite (calcium phosphate salt), calcium carbonate, magnesium, sodium, potassium, fluoride, sulfate, carbonate, and hydroxide.Bone TissueTwo Major Types of Bone Tissue:Compact- functions in support and protection. Structural Unit of Compact Bone- osteonOsteons are circular arrangements of boney tissue (comparable to the growth rings of a tree). There is little to no space between neighboring osteonsSpongy- functions in blood cell formation (location of red marrow) and some supportStructural Unit- trabeculae; interconnected plates of boney tissue. Spongy bone has large spaces in between neighboring trabeculae where the red marrow is found.Structure of Spongy BoneOsteocytes lie in boney plates called trabeculae. The osteocytes here get their nutrients by diffusion into this area from nearby blood supplies. These plates of bone (trabeculae) are separated by large voids or pores thus giving the bone a spongy appearance. Structure of Compact BoneMature bone cells (osteocytes) are located in areas of boney matrix which make concentric patternsaround a central canalwhere blood vessels are located. As bone is laid in concentric rings around the central canal the osteon forms. As osteons abut neighboring osteons compact bone is formed.Osteon Parts:•Central Canal-Also known as the harversian canals, these channels contain blood vessels and nerves. Thus providing a direct blood supply to this type of bone tissue.•Central canals are interconnected via transverse canals called perforating canals or Volkmann’s Canals. These canals allow blood flow and communication between neighboring osteons, the periosteum, and medullary cavity containing the endosteum and the central canals.
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- Fall '16