Formation of bone

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.

Steps in endochondrial ossification:

1.cartilageneous model

2. Formation of areolae:

Stages of Endochondrial ossification:

3.Calcification of matrix: 4.Formation of areolae:

Endochondrial ossification:formation of bony lamellae

Structural unit of bone: Lamellae

Primary center of ossification:

Secondary center of ossification:

Growth of bone in length:

Increase in thickness of long bone:

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

1.Stages of Intramembranous Ossification

Figure 6.7.1

2.Stages of Intramembranous Ossification

Figure 6.7.2

3.Stages of Intramembranous Ossification

Figure 6.7.3

4.Stages of Intramembranous Ossification

Figure 6.7.4

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.

THANK YOU

ANY QUESTIONS ???