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2. 6/28/2016ali mekki2 SPECIAL EMBRYOLOGY Development of the skeletal system

3. 6/28/2016ali mekki3 General objectives By the end of this lecture we can discuss : Development of the limbs and congenital anomalies Development of the vertebral column Development of the ribs and sternum Development of the muscular system

4. Membranous Cartilaginous Embryology of the skeletal system Types of bones according to the ossification

5. 1.Most of the bones of the skeleton are (cartilagious bones) 2.Only few of the bones of the body are membranous bones. 3.The mechanism of ossification is the same in both, the only difference is that a.In cartilaginous bone, ossification occurs in the place of dying cartilage and the U.M.cs come from the perichondrium b.In membranous bone,ossification occurs in a pice of CT membrane and the U.M.Cs come from the C.T membrane itself. Embryology of the skeletal system Facts to be remembered

6. Connective Tissue Disorders Collagen is the commonest form of body protein making up 90% of the non-mineral bony matrix. Some 20 types of collagen have been identified, those distributed in muscle skeletal system are: type 1: in bone, ligament, tendon and skin type 2: in cartilage. Type3:in blood vessels, muscle and skins.

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8. 6/28/2016ali mekki8 Development of the limbs Begins by the end of the 4 th week Formed by mesenchymal core Cover by ectoderm AER By the 6 th week the limb plates appears Digitation under control of cells in base of the limb (zone of polarizing activity)

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14. 6/28/2016ali mekki14 Limbs malformations Amelia and meromelia Phocomelia Micromelia Polydactyly Ectrodactyly Syndactyly Clubfoot Amniotic bands

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19. 6/28/2016ali mekki19 Malformation of vertebral column Scoliosis Lordosis Spina bifida -Occulta -Cystica -Chondroplasia dwarfism -Acromegaly

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21. 6/28/2016ali mekki21 Developments of the ribs and sternum The ribs developed from the costal process of the vertebra The sternum developed from the somatic mesoderm Begins by two bands called sternae The ribs may absent, increase in number or decrease Sternum may be clefted or short

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