ossification and bone cells

Document Sample
ossification and bone cells Powered By Docstoc
					                                                                                                    11/6/09




                                                      Endochondral Ossifica/on 
                                                       aka. Bone Development 
                                               •  Forma/on of all long bones, many short bones 
                                                  and some irregular bones 
         Skeletal System                       •  Process by which car/lage cells break down and 
    Ossifica/on and bone cells                     are replaced by bone cells and mineral salts 

                  Chapter 5.  




        Bone developement                                           Calcium
•  Bones form on hyaline cartilage model        •  PTH = parathyroid hormone
                                                •  Osteoclasts: breakdown bone
•  Ossification: bone formation
  –  1. Hyaline cartilage covered with bone-    •  When blood calcium is low
     osteoblasts lay down bone                  •  PTH secreted- stim osteoclasts
  –  2. Hyaline eaten away to make medullary
     cavity                                     •  When blood Ca is high
                                                •  Osteoblast stimulated by thyroid to build bone




                                                            Osteogenetor Cells 
               Bone cells:
                                               •  Where cells come from 
•  There are 4 types of cells in bone tissue
                                               •  Comes from mesenchyme 
  –  Osteoprogenetor cells
  –  Osteoblasts                               •  Produces massive amounts of unspecialized 
  –  Osteocytes                                   cells 
  –  osteoclasts                               •  Highly mito/c 
                                               •  This is when the cells start to differen/ate 




                                                                                                         1
                                                                                                            11/6/09




                     Osteoblasts                                       Osteocytes: 
•  Bud cells                                           •  Secreted by osteoblasts 
•  Where osteoprogenetor cells start o specialize      •  Found in the canaliculi 
   into bone cells                                     •  Work with the osteoblasts to break down the 
•  Begin the secre/on of mineral salts (calcium           bony matrix for reshaping  
   and phosphorus) 




                     Osteoclasts:                         Intermembranous Ossifica/on: 
•  Generally found in membranes of the bones           •  Membranes are laid down in layers 
  –  Periosteum                                        •  Traebiculae form between layers 
                                                         –  Red bone marrow found within the traebiculae 
•  The func/on of osteoclasts is to aid in the 
   development, growth, maintenance, and 
   repair by reabsorbing excess minerals to help 
   shape bone.  




                   Bone healing
 1. Hematoma: blood filled swelling
 2. Fibrocartilage callus: splints bone.
    Granulation tissue
    phagocytes

 3. Bony callus: more osteoblasts and osteoclasts to
    area
 4. Remodeling of bony callus due to mechanical
    stresses




                                                                                                                 2

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:6
posted:11/21/2011
language:Basque
pages:2