Ch. 7 Bones b

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  1. What is the primary bone cell that gives rise to the rest? What do these come from? Where are they located?
    Osteogenic cells, arises from mesenchymal cells. Found in the endosteum and inner surface of the periosteum.
  2. What are the cells that form bone or “B”uild it?
    Osteoblasts, B is for build. These are nonmitotic so are only formed from the mitosis and differentiation of osteogenic cells into osteoblasts. Found as a single layer under the endosteum and periosteum. These secrete the organic gel that makes bone what it is, along with the nonorganic matter.
  3. What is an Osteocyte?
    An osteoblast that is now trapped in its secretion. Only maintains the bone matrix by managing blood calcium, phosphate, and magnesium balance. The osteocyte is trapped in its “lacunae” and uses the arms/passages called canaliculi to contact other osteocytes and dump waste.
  4. What is the destroying bone cell?
    Osteoclasts (clast means destroy). These are cells of a slightly different origin than other bone cells. They typically have 3-4 nuclei. They also release enzymes and acids that dissolve the bone matrix (removes minerals). Etch their own little spot into the bone called a resorption bay.
  5. What is the organic matter of the bone matrix secreted by osteoblasts? What is the function of this?
    Osteoid. Its secretion contains, among other things, collagen which gives the bone a degree of flexibility, keeping it from breaking like chalk. Under stress the collagen has sacrificial bonds that protect the bone from fracturing.
  6. What is the majority of inorganic matter in the bone matrix? What is the function of the inorganic matter?
    Hydroxyapitite (crystalized calcium phosphate salt) is 85% of the inorganic matter. The inorganic matter makes the bone rigid and enables it to support the weight of the body without sagging.
  7. Describe spongy bone. Where is it found? what are the sponge parts called? What is in it?
    Hard bone despite sponge appearance. Found at the ends of long bones and within other types of bones. The sponge parts are called trabeculae. Red bone marrow lies in the spaces between trabeculae.
  8. What are the two bone marrows? What can one do that the other can’t?
    Red and yellow bone marrow. Red bone marrow is a living organ and produces blood cells. This turns into fatty yellow bone marrow as we get older.
  9. Where is Red bone marrow found?
    Nearly every bone in children. As adults its in the skull, vertebrae, ribs, sternum, proximal heads. Yellow bone marrow is found everywhere else
  10. Image Upload 1
    Concentric lamellae, connected by canaliculi and not to be confused with lacuna
  11. How are central canals connected?Image Upload 2
    perforating canals
  12. What is the structure of lamella?
    • Image Upload 3
    • collagen fibers corkscrewing in one direction while the fibers of neighboring lamella twist the other way
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Ch. 7 Bones b
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