Bone formation Flashcards
What are the two mechanisms of bone formation?
- Intramembranous ossification2. Endochondral ossification
In intramembranous ossification, where does bone form?
Directly within a membrane of highly vascular mesenchyme
What bones are formed by intramembranous ossification?
Flat bones - skull, face, mandible, clavicle, etc.
The highly vascular connective tissue surrounding bone spicules and trabeculae differentiates into ____________
Bone marrow
What bones are formed by endochondral ossification?
Long bones - limbs, vertebrae
Where is the primary ossification center located?
Diaphysis
What makes up the periosteal bud?
Blood vessels, osteoprogenitor cells, HSCs
Where is the secondary ossification center located?
Epiphysis
How does long bone growth occur in length?
Endochondral bone formation in epiphyseal plates
What are characteristics of the Zone of Reserve Cartilage?
- Typically hyaline cartilage2. Mitotically active
What are characteristics of the Zone of Proliferation?
- Intense mitosis2. New organic matrix (interstitial cartilage growth)
What are characteristics of the Zone of Hypertrophy?
- Chondrocytes accumulate glycogen and become vacuolated2. Cells and lacunae enlarge at expense of matrix
What are characteristics of the Zone of Calcified Cartilage?
- Lacunae coalesce2. Calcification of cartilage matrix3. Chondrocytes die
What are characteristics of the Zone of Resorption and Ossification?
- Calcified cartilage remnants form long spicules in direction of diaphysis2. Blood vessels bringing osteoprogenitor cells invade3. Osteoprogenitor cells emigrate to calciied cartilage matrix area, differentiate into osteoblasts
What color does calcified cartilage remnants stain?
Blue (hematoxylin)
