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Bone Formation, Growth and Remodeling

Bone Formation, Growth and Remodeling. Bone formation. The Skeleton is formed from two of the strongest and most supportive tissues in the body: Cartilage and bone In embryo: the skeleton is primarily make of hyaline cartilage In young child: most of the cartilage has been replaced by bone.

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Bone Formation, Growth and Remodeling

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  1. Bone Formation, Growth and Remodeling

  2. Bone formation • The Skeleton is formed from two of the strongest and most supportive tissues in the body: Cartilage and bone • In embryo: the skeleton is primarily make of hyaline cartilage • In young child: most of the cartilage has been replaced by bone

  3. Bone formation • Except for flat bones, which form on fibrous membranes, most bones develop using hyaline cartilage structure as their “models” • Ossification: Bone formation Step 1. The hyaline cartilage model is completely covered with bone matrix by bone-forming cells called osteoblasts Step 2. The enclosed hyaline cartilage model is digested away, opening up a medullary cavity within the newly formed bone

  4. Long bone growth • The epiphyseal plates provide for longitudinal growth of the long bones during childhood: • “New” Cartilage is formed continuously on the external face of the articular cartilage and on the epiphyseal plate surface that is farther away from the medullary cavity • “Old” cartilage on the internal face of the articular cartilage and medullary cavity is broken down and replaced by bony matrix

  5. Bone remodeling • Bones are remodeled continually in response to changes in two factors: • Calcium levels in the blood (determines whento break down or form bones) • The pull of gravity and muscles on the skeleton (determines where to break down or form bones)

  6. The Skeletal System • Forming / Molding Bone: • Osteoblasts: • Cells that rebuild your bones • Create new bone cells • Takes free floating Calcium and converts it into bone

  7. The Skeletal System • Forming / Molding Bone: • Osteoclasts: • Cells that release calcium from the bone into the blood system • Increase calcium in the blood • Parathyroid Hormone (PTH) activates Osteoclasts

  8. Simple • Bone breaks cleanly, but does not penetrate the skin • Sometimes called a “closed fracture”

  9. Compound • Broken ends of the bone protrude through soft tissues and the skin • Sometimes called an “open fracture”

  10. Communited • Bone breaks into many fragments • Particularly common in the aged, whose bone are more brittle

  11. Spiral • Ragged break occurs when excessive twisting forces are applied to a bone • Common sports fracture

  12. Greenstick • Bone breaks incompletely, much in the way a green twig breaks

  13. Compression/Depressed/Impacted • Compression: Bone is crushed • Depressed: Broken bone portion is pressed inward • Impacted: Broken bone ends are forced into each other

  14. Stages in the healing of a bone fracture 1. Blood vessels rupture. A blood filled swelling called a hematoma forms. Bone deprived of nutrition die. 2. Break is splinted. Growth of new capillaries. Disposal of dead tissue. 3. Fibrocartilage is replaced by spongy bone called a bony callus. 4. Bony callus is remodeled over the next few months in response to stress.

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