Formation of Bone
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Bone is a specialized connective tissue composed of cells, fibers, and minerals. It forms through two processes: endochondral ossification and intramembranous ossification. Endochondral ossification involves cartilage models that are replaced by bone, forming long bones and portions of flat bones. It begins in the second month of development. Intramembranous ossification involves mesenchymal cells directly forming bone, without a cartilage intermediate, forming bones like the skull and clavicle. Bone growth is regulated by hormones like growth hormone and sex hormones. Common bone diseases include osteogenesis imperfecta and achondroplasia.
Formation of Bone
- 2. General overview: Bone Specialized connective tissue Components of bone: Cell:osteogenic cell,osteoblast,osteocytes,osteoclast Fibres:collagen type –I Ground substanse:chondroital sulphate,keratin sulfate and glycoprotein Minerals:calcium phosphate,hydroxy apatite crystal of calcium phosphate
- 3. Formation of bone: Mesodermal in origin Formed by process of ossification a. Endochondrial ossification(cartilagenous model) b. Intramembranous ossification(membranous model)
- 4. Law of ossification: secondary center which appears first unites last with diaphysis and secondary center which appears last unites first with diaphysis Exception: Fibula Primary center forms diaphysis whereas secondary center forms epiphysis
- 5. 1.Endochondrial ossification: Begins at second month of embryonic development Hyaline cartilage is subsequently replaced by bone Leads to Growth in length and width of bone Bones formed are known as cartilage bones Formation of short and long bones.
- 6. Steps in endochondrial ossification: 1.cartilageneous model 2. Formation of areolae:
- 7. Stages of Endochondrial ossification: 3.Calcification of matrix: 4.Formation of areolae:
- 9. Structural unit of bone: Lamellae
- 10. Primary center of ossification:
- 12. Growth of bone in length:
- 13. Increase in thickness of long bone:
- 14. Intramembranous ossification: Mesenchymal cells directly converts to osteoblasts with capillaries in center of ossification Mostly forms flat bones e.g: formation of mandible, maxilla, clavicle and most of flat bones of skull Begins at 8th week of development
- 19. Hormonal regulation of bone formation: 1) Human growth hormone: Bone growth before puberty 2) Sex hormones(testosterone and estrogen) Development of typical male and female shaped skeleton after puberty. 3)Parathyroid hormones:release of calcitonin
- 20. Clinical Anatomy: Dyschondroplasia or enchondromatosis Achondroplasia diaphyseal aclasis Osteogenesis imperfecta Cleido-cranial dysostosis Fibrous dysplasia Osteosclerosis Dwarfism gigantism
- 21. REFERENCES: Langman’s medical embryology,9th edition Singh Inderbir, G.P pal, human embryology, ninth edition,2012 Keith L.moore, The developing human, clinically oriented embryology,8th edition Krishna Garg,Indira Bahl,Mohini Kaul A text book of histology,a colour atlas and text, 3rd edition Basic histology, text and atlas,11th edition,2005 penny(2012), bone development, retrieved on 26th April, 2014.
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