Martini Chapter 6

Martini Chapter 6

1. 5 Primary functions

   • Support - provides structural support for the body and provides the framework for attachments of tissues and organs
   • Storage of Lipids and minerals - stored in the yellow bone marrow
   • Blood Cell Production - produced in the red bone marrow
   • Protection - protects soft organs from damage
   • Leverage - act as levers that change the magnitude and direction of the forces generated by skeletal muscles

2. Bone Shapes and Structures

   • Bone Shapes
     • Sutural bones - small, flat, irregularly shaped bones between the flat bones of the skull
     • Irregular bones - complex shapes with short, flat, notched or ridged surfaces
     • Short bones - small and boxy
     • Flat bones - thin, parallel surfaces, provide protection for underlying soft tissues
     • Long bones - long and slender
     • Sesamoid bones - small, flat and shaped like a sesame seed
   • Bone Markings
     • bone markings are surface features
     • these markings can be used to identify the size, age, sex and general appearance
   • Bone Structure
     • Diaphysis - extended tubular shaft
     • Epiphysis - expanded area at the end of a bone
     • Metaphysis - the join between the diaphysis and epiphysis
     • the wall of the diaphysis is a layer of compact bone, dense bone
     • Compact bone forms a protective layer that surrounds the medullary cavity, marrow cavity
     • The epiphyses contain spongy bone
     • Spongy bone is an open network of struts and plates that form a lattice structure with a layer of compact bone, cortex.
     • A flat bone is a sandwich of compact bone covering a core of spongy bone
     • In the skull the layer of spongy bone is called the diploe

3. Bone is Composed of Several Cell Types

   • Bone Matrix
     • Calcium phosphate makes up 2/3 of the weight of a bone
     • Calcium phospate interacts with calcium hydroxide to form crystals hydroxyapatite, as they form they incorporate other calcium salts and ions.
     • 1/3 of the weight of a bone is collagen fibres
     • Cells only make up 2% of a bones mass
     • Calcium phosphate crystals are hard and brittle so shatter and break when bent, twisted or recieve a sudden impact
     • Collagen fibres are strong and when pulled they are strong as steel, they are also flexible but can't cope with compression
     • The composition of the matrix in compact is the same as in spongy bone
     • Collagen form the backbone for the calcium phosphate crystals to form on
     • The crystals form and lock the bone into shape
   • Bone Cells
     • Osteocytes
       • mature bone cells
       • each osteocyte occupies a lacuna
       • the layers between them are called lamellae
       • narrow passageways called canaliculi go through the lamellae and connect the lacunae with sources of nutrients
       • osteocytes are linked by gap junctions which allow the exchange of ions and small molecules
       • the interstitial fluid provides an additional route for diffusion
       • 2 functions
         • maintain the protein and mineral content of the surrounding matrix
         • participate in the repair of damaged bone
     • Osteoblasts
       • Osteoblasts produce new bone matrix during ossification or osteogenisis
       • they make and release the proteins ando ther organic components of the matrix
       • before calcium salts are deposited the organic matrix is called osteoid
       • 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
       • osteocytes are formed when a osteoblast is completely surrounded by bone matrix