Martini Chapter 6

5 Primary functions
1. Support - provides structural support for the body and provides the framework for attachments of tissues and organs
2. Storage of Lipids and minerals - stored in the yellow bone marrow
3. Blood Cell Production - produced in the red bone marrow
4. Protection - protects soft organs from damage
5. Leverage - act as levers that change the magnitude and direction of the forces generated by skeletal muscles
Bone Shapes and Structures
1. Bone Shapes
  1. Sutural bones - small, flat, irregularly shaped bones between the flat bones of the skull
  2. Irregular bones - complex shapes with short, flat, notched or ridged surfaces
  3. Short bones - small and boxy
  4. Flat bones - thin, parallel surfaces, provide protection for underlying soft tissues
  5. Long bones - long and slender
  6. Sesamoid bones - small, flat and shaped like a sesame seed
2. Bone Markings
  1. bone markings are surface features
  2. these markings can be used to identify the size, age, sex and general appearance
3. Bone Structure
  1. Diaphysis - extended tubular shaft
  2. Epiphysis - expanded area at the end of a bone
  3. Metaphysis - the join between the diaphysis and epiphysis
  4. the wall of the diaphysis is a layer of compact bone, dense bone
  5. Compact bone forms a protective layer that surrounds the medullary cavity, marrow cavity
  6. The epiphyses contain spongy bone
  7. Spongy bone is an open network of struts and plates that form a lattice structure with a layer of compact bone, cortex.
  8. A flat bone is a sandwich of compact bone covering a core of spongy bone
  9. In the skull the layer of spongy bone is called the diploe
Bone is Composed of Several Cell Types
1. Bone Matrix
  1. Calcium phosphate makes up 2/3 of the weight of a bone
  2. Calcium phospate interacts with calcium hydroxide to form crystals hydroxyapatite, as they form they incorporate other calcium salts and ions.
  3. 1/3 of the weight of a bone is collagen fibres
  4. Cells only make up 2% of a bones mass
  5. Calcium phosphate crystals are hard and brittle so shatter and break when bent, twisted or recieve a sudden impact
  6. Collagen fibres are strong and when pulled they are strong as steel, they are also flexible but can't cope with compression
  7. The composition of the matrix in compact is the same as in spongy bone
  8. Collagen form the backbone for the calcium phosphate crystals to form on
  9. The crystals form and lock the bone into shape
2. Bone Cells
  1. Osteocytes
    1. mature bone cells
    2. each osteocyte occupies a lacuna
    3. the layers between them are called lamellae
    4. narrow passageways called canaliculi go through the lamellae and connect the lacunae with sources of nutrients
    5. osteocytes are linked by gap junctions which allow the exchange of ions and small molecules
    6. the interstitial fluid provides an additional route for diffusion
    7. 2 functions
      1. maintain the protein and mineral content of the surrounding matrix
      2. participate in the repair of damaged bone
  2. Osteoblasts
    1. Osteoblasts produce new bone matrix during ossification or osteogenisis
    2. they make and release the proteins ando ther organic components of the matrix
    3. before calcium salts are deposited the organic matrix is called osteoid
    4. osteoblasts help elevate concentrations of calcium phosphate above its solubility limit which triggers the deposition of calcium salts into the matrix which converts the osteoid to bone
    5. osteocytes are formed when a osteoblast is completely surrounded by bone matrix

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Martini Chapter 6

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