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

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

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

Literacy Activity-Pair and Share

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

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.

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)

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

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

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

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Endochondral Bone

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

Bone Formation and Growth Figure 6–12 Intramembranous Ossification.

Bone Formation and Growth

Ossification Ossification

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.

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

Bone Formation and Growth Figure 6–10 Endochondral Ossification.

Bone Formation and Growth

4 6 2 5 A 1 3

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

Bone Formation and Growth

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

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)

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.

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.

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

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