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What is the purpose of bone?
- Support - framework
- Movement - muscles attachment
- Protection - internal organs
- Mineral homeostasis - calcium, phosporus, magnesium
- Lipid storage - yellow marrow
- Blood Cell production - bone marrow
What is bone made of?
extracelluar matrix and cells
What is extracellular matix?
- Organic matrix - 30% - containing proteoglycans and collagen fibers
- 25% of bone is water
- 70% of bone is made up of HYDROXYAPATITE
What are cells?
Osteoblasts and Osteocytes, osteoprogenitor cells and osteoclasts.
What are the properties of bone?
- resistant to bending, twisting, compression and stretch
- calcified highly vascular, regenerative ability
What are flat bones?
parallel to the surface of the body and have protective functions. broad attachemnt area.
What are long bones?
weight bearing, curved and strong, compact and spongy, limbs composed of these
What are short bones?
compact on surface with spongy centers. wrist, ankle bones
What are irregular bones?
vertebra and facial bones
What are sesamoid bones?
embedded in tendons to change the direction of movement, patella
What is spongy bone?
- - found at the expanded heads of long bones and fills most irregular bones.
- - lighter and more dense
- -consists of trabeculae
What is compact bone?
- -forms the outer shell
- -consists of closely packed osteons or Haversians System
What is an osteon?
Consists of a central canal called an osteonic (haversians) canal which is surrounded by lamellae of matric
What does the periosteum consist of?
- - collagen fibers
- - fibroblasts
What does the endosteum consist of?
- a single layer of osteoprogenitor cells and connective tissue
What is an osteoid?
extracellular matrix which is not calcified.
When does calcification occur?
With th presense of collagen fibers. Osteoblasts build up the bone. (osteoclasts remodel bone)
What are the two ways bones can grow?
- Endochonral - formation of bone onto a temporary cartilage model of scaffold. all long bones develop this way except clavicle
- Intramembranous - formation of bone directly onto fibrous connective tissue (flat bones of skull, mandible, maxilla clavicle)
Where is the only place bone growth occurs?
Epiphyseal Plate - stimulared by growth hormone - place between the metaphysis and epiphysis
What happens during a bone fracture?
- - first thing is severe bleeding.
- - osteoprogenitor cells in periosteum will form osteoblasts, these cells will for fragments of bone within the clot called CALLUS
- - The osteoblasts will form bone between fracture ends called COLLAR BONE