Elastic fibres

INDIA

1. ELASTIN Preethi chekuri

2. ELASTIC FIBRES Integral component of dermal connective tissue It provides resilience & elasticity to the skin These are relatively minor component in normal sun- protected adult skin less than 2–4% of the total dry weight of the dermis. Reticular dermis : fibres consists of horizontally oriented fibres which interconnect to provide a network structure.

3. FUNCTIONS Extensibility Elasticity Resilience

4. CONVENTIONAL MICROSCOPY Oxytalan fibres Elaunin fibres Elastic fibres

5. OXYTALAN FIBRES More superficial Thin & oriented perpendicular to dermo epidermal junction Ultrastructurally : composed of bundles of tubular microfibrils 11 nm in diameter

6. ELAUNIN FIBRES Thin fibres which form a plexus within papillary dermis parallel to dermo – epidermal junction Spherules of elaunin that punctate this plexus are called elastic globes. These are connected to elastic fibres of reticular dermis that are alligned parallel to skin surface

7. LASER SCAN MICROSCOPY

8. ELASTIN Initially synthesized as precursor polypeptide : tropoelastin Consists of approximately 700 aminoacids with molecular mass of 700 kDa It is one of the component of reticular dermis

9. ELECTRON MICROSCOPY An amorphous electroluscent core Microfibrils - electron dense fibrils of insoluble glycoprotein complexes 11nm diameter

10. BIO CHEMICALLY Elastin consists of linear ,polypeptide tropoelastin subunits whose m.wt 72,000daltons rich in valine , proline & alanine It does not contains hydroxylysine or covalently linked sugar residues & 1% of it is composed of hydroxyproline

11. Amino Acids in Elastin Composed of amino acids. Valine , Glycine, Alanine and Proline .

12. BIO SYNTHESIS Biosynthesis of fibres by fibrocytes : 1.microfibrils of elastic fibres secreted in form of grouped linear arrays in long cylindrical infolding of cell surface,where polymerization occurs. 2. newly synthesized , soluble,tropoelastin polypeptides are secreted by fibrocytes into the pre-formed cylinder of microfibrils By means of complex process that involves enzyme lysyl oxidase polypeptides are linked by formation of cross links : desmosines or isodesmosines

13. Secondary Structure

14. Four lysine chains can be combined to form a desmosine cross-link

15. CYTOKINE & HORMONAL REGULATION Inflammatory mediators modulate elastin gene expression They play a role in diseaes charecterized by accumulation of elastic fibres in tissues Vitamin D3 modulates gene expression Incubation of fibroblast with vit D3 results in 80-90% decrease in total distribution of tropoelastin Insulin like growth factor enhances gene expression

16. IMAGE OF ELASTIC FIBRES

17. TISSUE DISTRIBUTION Lungs Elastic ligaments Skin Bladder Elastic cartilage Blood vessels

18. Elastic fibres absent in : scars : keloid : dermatofibromas Decreased or absent in anetoderma

19. CLINICAL SIGNIFICANCE Marfan syndrome Emphysema caused by alpha -1 anti trypsin deficiency Atherosclerosis Menkes syndrome Pseudo xanthoma elasticum Williams syndrome

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