Bone(2)

Bone Formation,growth, and Remodeling

• Osteon (haversian system)• lamellae• perforating fibers• compact bone• blood vessels• periosteum• central canal• perforating canal• blood vessel

Parts of Compact Bone

• lamella• osteocyte• lacuna• canaliculus• matrix• spongy bone

Microscopic structure of compact bone

Long bone formation growth

common types of fractures

- bone breaks into many framents.

Comminuted

Compression

-bone is crushed

Depressed

-broken bone portion is pressed inward

Impacted-broken bone ends are forced int each

othe.

Green stick

-bone breaks incompletely, much in the way a green twig breaks.

Stages in the healing of a bone

The repair of bone fractures involves four major events

1.A hematoma is formed-blood vessels are ruptured when the bone breaks. as a result a blood-filed swelling called a hemaoma forms. Bone cells deprived of nutrition die.

2.The breka is splinted by a fibrocartilage callus-an early event of tissue repair (and bone is no exception)is growthbof new capillaries into the clotted blood at the site of the damage, and the disposal of dead tissue by phagocyctes.

as this goes on, connective tissue cells of various types form a mass of repair tissue, the fibrocartilage callus that contains several elements -some cartilage matrix, some bony matrix ,and collagen fibers-and acts to ''splints'' the broken bone,closing the gap.

3.The bony callus is formed as more osteoblasts and osteoclasts migrate into the area and multiply,the fibrocartilage callus is gradually replaced by one made of spongy bone,the bony callus.

4.bone remodelling occurs-over the next few weeks to month depending onthe bone's size and site of the break, the bony callus is remodeled in response to the mechanical stresses placed on it, so that it forms a strong permanent ''patch'' at the fracture site.