Bones Growth and Broken Bones

Listed below are a couple notes that I felt were important when it came to bones. Also I listed notes on the fractures of bones and their healing process. Enjoy!


Bone Types/classification:

• axial skeleton
• appendicular skeleton
• long bones (longer than they are wide)
• short bones (cubed shaped bones/ form within tendons)
• flat bones (flattened, mainly in the skull)
• irregular bones (have complicated shapes

Chemical Composition of Bone:

• osteoblasts- bone forming cells
• osteocytes- mature bone cells
• osteoclasts- large cells that break down or resorb bone matrix
• osteoid- unminerlized bone matrix composed of proteoglycans, glycoproteins, and collagen

Bone Development:

• osteogenesis and ossification- the process of bone tissue formation which leads to:
• the formation of bony skeleton in the embryo
• bone growth until early adulthood
• bone thickness, remodeling, and repair

Functional Zones:

• growth zone- where the cartilage cells undergo mitosis
• transformation zone:
1. older cells enlarge 
2. matrix becomes classified
3. cartilage cells die
4. matrix begin to deteriorate
• osteogenic zone- new bone formation occurs
• Cartilage grows and then bone replaces it 

bone is resorbed and added by appositional growth as shown

Appositional Growth of Bone:

Bone Remodeling: 

• Remodeling units- adjacent osteoblasts and osteoclasts deposit and resorb bone at periosteal and endosteal surfaces

Control of Remodeling: 

• Two control loops regulate bone remodeling
• hormonal mechanism maintains calcium homeostasis in the blood
• mechanical and gravitational forces acting on the skeleton

Broken Bones

• classified
• the position of the bone ends after the fracture
• the completeness of the break
• the orientation of the bone to the long axis
• wether or not the bones ends penetrate the skin
• nondisplaced:
• bone ends retain their normal position 
  
• Displaced:
• bone ends are out of normal alignment      
  
       
• Complete:
• bone is broken all the way through 
  
• Incomplete:
• bone is not broken all the way through    
  
• Linear:
• the fracture is parallel to the long axis of the bone  
  
• Common types of fractures:
• comminuted
• spiral
• depressed
• compression
• epiphyseal
• greenstick
• Stages in Healing Fractures/Breaks:
• Hematoma formation:
1. torn blood vessels hemorrhage
2. a mass of clotted blood forms at the fracture site
3. site becomes swollen, painful, and inflamed
• Fibrocartilaginous callus forms
• granulation tissue forms a few days after the fracture
• capillaries grow into tissue and phagocytic cells begin cleaning debris
• bony callus formation 
• bone remodeling