Bone Development
Bone development begins in the embryo by two distinct processes : 1- Intramembranous Ossification : Mandible , Maxilla , Clavicles , most of the flat bones of the skull2- Endochondral Ossification : In Developing long bones
Bone Cells1- Osteoprogenitor ( Osteogenic ) cells : Found in the inner layer of periosteum and in the single layer of endosteum . 2- Osteoblasts ( Bone Forming Cells ) Found on the surfaces of bone 2- Osteocytes : Found in lacunae in the trabeculae of bone
4- Osteoclast cells : Large Multinucleated cells giant found in Howships lacunae along bone surfaces
Intramembranous ossification
Intramembranous OssificationMesenchymal cells
Osteoblast
Osteoid
Bone marrow cavity
Trabeculae
Osteocytes
Intramembranous Ossification
OsteoblastOsteoid
Mesenchymal cells
Trabeculae
Bone marrow cavity
osteocytes
Intramembranous Ossification
Mesenchymal cellsOsteoblast
Osteoid
Trabeculae
osteocytes
Endochondral Ossification
Long bones consist of shaft called diaphysis and two ends each called epiphysis The primary ossification center first appear in the diaphysis followed by a secondary ossification center in the epiphysis . Cartilage is replaced by bone . 1- Zone of Reserve cartilage 2- Zone of Proliferation 3- Zone of Maturation and Hypertrophy 4- Zone of Calcification 5- Zone of Erosion 6- Zone of Ossification: Osteoblasts 7- Zone of Resorption : OsteoclastsEndochondral Ossification
Endochondral Ossification
Endochondral OssificationResting zone
Proliferation zone
Maturation zone
Hypertrophy zone
Ossification zone
Vascular invasion
Endochondral Ossification
Blood vessels from the perichondrium penetrating the calcified cartilageEndochondral Ossification
osteocyteosteoclast
Howships lacunae
Resorption zone
Endochondral Ossification
Endochondral OssificationEndochondral Ossification
Endochondral OssificationEndochondral Ossification
PeriosteumOsteogenic cells
Osteoblasts
Bone collar
Endochondral Ossification
Ossification zoneMaturation and Hypertrophy zone
Zone of Reserve cartilage
Zone of ProliferationZone of Maturation and Hypertrophy
Endochondral Ossification
Zone of Ossification
Zone of ResorptionEndochondral Ossification
Osteoclast