1. Slow, continuous growth of the epiphyseal plate cartilage

   1. Chondrocytes near the diaphysis hypertrophy  die  calcified

   2. CARTILAGE GROWS AWAY FROM DIAPHYSIS

   3. Metaphysis—conversion of cartilage to bone

2. Elongation of the diaphysis

3. Replacement of cartilage with bone.

4. Can tell difference in H&E because calcified cartilage is basophilic and bone is acidophilic

Appositional growth also occurs to maintain constant diameter.

Stages of Chondrocyte Development

1. Uppermost – resting

2. Dividing cells – isogenic nests

3. Mature Chondroblasts – produce cartilage

4. Hypertrophied and dying cells – larger lacunae

5. Calcified matrix surrounding cells - Metaphysis

6. Replacement of cartilage by bone

Blood Vessel Involvement

1. Chondroclasts drill into calcified matrix

2. Blood vessels follow

3. Osteoblasts form

4. Bone deposited on calcified cartilage

Flat Bones Grow in Thickness, Flat Bones in Diameter

The outer surface enlarges by intramembranous ossification

(osteoblasts)

Osteoclasts on the inside break down bone => enlarging the

medullary cavity

Thickness of cortex increases slightly as bone thickens

Blood vessels that enter the Periosteum become incorporated

into Volksman’s canals

Remodeling converts immature bone into compact bone

Sutures are DICT

Fontanelles are mesenchymal membranes that have not been

converted to bone

Remodeling must occur in the skull because the curvature must

be reduced to accommodate the growing brain.

Long bones must be remodeled as the individual grows.

Category: Orthopedics Notes