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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
Formation of bone:
Mesodermal in origin Formed by process of ossificationa. Endochondrial
ossification(cartilagenous model)b. Intramembranous
ossification(membranous model)
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
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.
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
Hormonal regulation of bone formation:
1) Human growth hormone: Bone growth before puberty2) Sex hormones(testosterone and
estrogen) Development of typical male and
female shaped skeleton after puberty.3)Parathyroid hormones:release of
calcitonin
Clinical Anatomy:
Dyschondroplasia or enchondromatosis Achondroplasia diaphyseal aclasis Osteogenesis imperfecta Cleido-cranial dysostosis Fibrous dysplasia Osteosclerosis Dwarfism gigantism
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.