1. Aim: How can we describe the steps of endochondral ossification?
DO NOW:
Review
HW-
Endochondral ossification due tomorrow
Review packet due on Thursday
Test on Friday

3. Bone Formation and Growth
Bone Development
Human bones grow until about age 25
Osteogenesis
Bone formation
Calcification
The process of depositing calcium salts
Occurs during bone ossification and in other tissues

4. Bone Formation and Growth
Bone Development
Ossification
The process of replacing other tissues with bone
The two main forms of ossification are
intramembranous ossification
endochondral ossification

5. Literacy Activity-Pair and Share

6. Define Endochondral ossification
Ossifies bones that originate as hyaline cartilage
Occurs in most bones of the body

7. Explain the events of the cartilage model.
Cartilage expands and chondrocytes enlarge then die and disintegrate leaving cavities within cartilage
Blood vessels grow into perichondrium (surface of cartilage)
Osteoprogenitor cells differentiate into osteoblasts , which start to lay down matrix.

8. Define primary ossification center
Define primary ossification center. Where is it located and briefly describe the events that take place there?
Occurs in the diaphysis
Bone Development begins in the Primary Ossification Center- Spongy Bone
No Medullary Cavity
Development of medullary Cavity due to osteoclasts
Growth continues in length(interstitial growth) and diameter(appositional growth)

9. Define secondary ossification
Define secondary ossification. Where is it located and briefly describe the events that take place there?    
Capillaries and osteoblast migrate into the epiphyses creating secondary ossification centers.
The epiphyses becomes filled with spongy bone
Articular cartilage- remnants of cartilage
Prevents bone to bone contact within joint

10. Explain the significance of the epiphyseal plate.
Epiphyseal cartilage (plate) separates epiphysis and diaphysis.
Remains cartilage until growth ends
Epiphyseal Lines
When long bone stops growing, after puberty
Epiphyseal cartilage disappears
Is visible on X-rays as an epiphyseal line

11. Bone Formation and Growth
Figure 6–11 Bone Growth at an Epiphyseal Cartilage.

12. A C D B F E

13. Endochondral Bone

14. Intramembranous Ossification
bones such as mandible (lower jaw)
Clavicle (collarbone)
Soft Spots

15. Bone Formation and Growth
Figure 6–12 Intramembranous Ossification.

16. Bone Formation and Growth

17. Ossification
Ossification

18. Summary
The ______________________ nutrient artery penetrates the _____________________, which is converted to the ___________________ of bone.
Primary ossification begins in the __________________________ of bone.
Secondary ossification takes place in the _______________________.
True or False
4. Intramembranous ossification forms long bones.
5. Endochondral ossification does not begin with mesenchymal cells.
6. Spongy bone is laid down before compact bone during ossification.

19. Bone Formation and Growth
Epiphyseal Lines
When long bone stops growing, after puberty
Epiphyseal cartilage disappears
Is visible on X-rays as an epiphyseal line
Mature Bones
As long bone matures
Osteoclasts enlarge medullary (marrow) cavity
Osteons form around blood vessels in compact bone

20. Bone Formation and Growth
Figure 6–10 Endochondral Ossification.

21. Bone Formation and Growth

22. 4 6 2 5 A 1 3

23. 1
Articular cartilage
Spongy bone
Epiphyseal plate
Secondary
ossification
center
Nutrient
artery and vein
Uncalcified
matrix
Epiphyseal
artery and
vein
Formation of articular cartilage
and epiphyseal plate
Development of secondary
ossification center
Development of
cartilage model
primary ossification
the medullary
cavity
Growth of 2 3 4 5 6
Hyaline
cartilage
Calcified
Periosteum
(covering
compact bone)
Medullary
artery
Perichondrium
Proximal
epiphysis
Distal
Diaphysis
Primary
Spongy
bone 1
Development of
cartilage model
primary ossification
center
the medullary
cavity
Growth of 2 3 4
Hyaline
cartilage
Calcified
matrix
Periosteum
(covering
compact bone)
Uncalcified
Medullary
Nutrient
artery and vein
artery
Perichondrium
Proximal
epiphysis
Distal
Diaphysis
Primary
ossification
Secondary
Epiphyseal
artery and
vein
Development of secondary
ossification center 5
Spongy
bone 1
Hyaline
cartilage
Calcified
matrix
Periosteum
(covering
compact bone)
Uncalcified
Medullary
cavity
Nutrient
artery and vein
artery
Perichondrium
Proximal
epiphysis
Distal
Diaphysis
Development of
cartilage model
primary ossification
center
the medullary
Growth of
Primary
ossification 2 3 4
Spongy
bone 1
Development of
cartilage model
primary ossification
center
Growth of 2 3
Hyaline
cartilage
Uncalcified
matrix
Calcified
Nutrient
artery
Perichondrium
Proximal
epiphysis
Distal
Diaphysis
Periosteum
Primary
ossification
Spongy
bone 1
Development of
cartilage model
Growth of 2
Hyaline
cartilage
Uncalcified
matrix
Calcified
Perichondrium
Proximal
epiphysis
Distal
Diaphysis 1
Development of
cartilage model
Hyaline
cartilage
Perichondrium
Proximal
epiphysis
Distal
Diaphysis

24. Bone Formation and Growth

25. Steps of Endochondral ossification
Chondrocytes (cartilage cells)increase in size
Chondrocytes die
Step 2
Blood vessels grow into perichondrium (surface of cartilage)
Cells of perichondrium convert to osteoblasts.
Osteoblasts convert perichondrium to periosteum

26. Steps of Endochondral ossification
Blood vessel penetration
Fibroblast Osteoblast
Bone Development begins in the center
Primary Ossification Center- Spongy Bone
No Medullary Cavity
Step 4
Development of medullary Cavity
Growth continues in length(interstitial growth) and diameter(appositional growth)

27. Steps of Endochondral ossification
Capillaries and osteoblast migrate into the epiphyses creating secondary ossification centers.
Step 6
The epiphyses becomes filled with spongy bone
Articular cartilage- remnants of cartilage
Prevents bone to bone contact within joint
Epiphyseal cartilage (plate) separates epiphysis and diaphysis.

28. Growth in Length- Interstitial Growth
The growth in length of long bones involves two major events:
1) Growth of cartilage on the epiphyseal plate
2) Replacement of cartilage by bone tissue in the epiphyseal plate
Copyright 2009, John Wiley & Sons, Inc.

29. Bone Formation and Growth
Appositional growth
Compact bone thickens and strengthens long bone with layers of circumferential lamellae
Endochondral Ossification

30. Bone Formation and Growth
Epiphyseal Lines
When long bone stops growing, after puberty
Epiphyseal cartilage disappears
Is visible on X-rays as an epiphyseal line
Mature Bones
As long bone matures
Osteoclasts enlarge medullary (marrow) cavity
Osteons form around blood vessels in compact bone