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31 Cards in this Set

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2 main types of ossification?
Direct & indirect
Direct ossification?
Intramembranous ossification
Main feature of intramembranous ossification?
Direct mineralization of matrix secreted by oseteoblasts
Main feature of indirect ossification?
Deposition of bone matrix on already existing cartilage matrix
Indirect ossification?
Endohondral ossification
Endochondral ossification?
Indirect ossification
Main feature of endochondral ossification?
Deposition of bone matrix on already existing cartilage matrix
Where is starting point of intramembranous ossification?
Ossification center
What happens in ossification centers of intramembranous ossification?
Mesenchymal cells condensate into a bone blastema
Intramembranous ossification; mesenchymal cells differentiate into and produce?
Osteoblasts -> Produce osteoid
steps in intramembranous ossification?
1. Mesenchymal cells differentiate to osteoblasts
2. Produce osteoid
3. Osteoid is mineralized by Ca2+& phosphate
4. Bone matrix of trabeculae formed
5. They fuse => Woven bone
First bone to be formed in intramembranous ossification?
Primary, woven bone
Between the trabeculae in primary woven bone - we find?
Bone marrow
How does primary woven bone become secondary mature compact bone (intramembranous ossification)?
During remodeling:
- Osteocalsts absorbs
- Osteoblasts deposit
How does the ossification centers grow in intramembranous ossification?
Radially - and fuse together
7 steps of chondral ossification (before osteoclasts begin to eat cartilage)
1. Chondrocytes in cartilage hypertrophy in fight for nutrition
2. Matrix gets reduced & calcified
3. Due to calcification O2 diffusion is impossible
4. Chondrocytes therefore undergo hypoxia
5. Due to hypoxia they release "sos" message
6. "SOS" message induce ingrowth of periosteal bud
7. With the bud joins mesenchymal & blood cells
8 steps of endochondral ossification (after periosteal bud has grown into cartilage)
1. Mesenchymal chondroclasts eat mineralized cartilage matrix
2. From this the medullary cavity is formed where mesenchymal & blood cells enter
3. Remnants become cartilage plates which becomes attachment points for osteoblasts
4. Osteoblasts start producing osteoid => Osteocytes
5. Bony spicules formed = Primary woven bone
6. Osteoclasts eat bony spicules (in a Howship´s lacunae)
7. Mineralized osteoid disposed by osteoblasts
8. MATURE SECONDARY LAMELLAR BONE :D
Function of bone collar around cartilage?
Prevent diametral growth, ensure longitudinal growth
Interstitial chondrocyte growth grow longitudinally because of?
Bone collar
Epiphyseal growth plate separates?
Diaphyseal & epiphyseal growth front
Chondrocytes on epi-side of epiphyseal growth plate?
Proliferate (end up as articular hyaline cartilage - because as dia-side becomes bone and "push" epi side towards end)
Chondrocytes on dia-side of epiphyseal growth plate?
Degenerate & replaced by bone
Name the 8 ossification zones?

1. Runka
2. På
3. Hestens
4. Ctore
5. Ereksjon
6. Og
7. Oppdaget
8. Resultatet
1. Resting zone
2. Proliferating zone
3. Hypertrophic zone
4. Calcification zone
5. Erosion zone
6. Osteogenic zone
7. Ossification zone
8. Resorption zone
Resting zone?
Hyaline cartilage
Small isogenic chondrocyte groups
Loads of matrix
Proliferating zone?
Mitotic division, ch.cytes stack on top of each other cause Ø-growth is impossible
Hypertrophic zone?
Ch. cytes enlarge - lack of nutrition => Die
Calcification zone?
Due to hypoxia, cartilage matrix is mineralized => Prim. bone(?)
Erosion zone?
Chondroclasts eat uncalcified intercellular areas
Osteogenic zone?
Osteoblasts are living on surfaces of primary bony spicules & secrete osteoid
Ossification zone?
Osteoid is mineralized
Resorption zone?
Osteoclasts in Howship´s lacunae resorbs bone => Dispose 2ndary bone!