ELASTIN

Preethi chekuri

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.

FUNCTIONS

• Extensibility

• Elasticity

• Resilience

CONVENTIONAL MICROSCOPY

• Oxytalan fibres

• Elaunin fibres

• Elastic fibres

OXYTALAN FIBRES

• More superficial• Thin & oriented perpendicular to dermo

epidermal junction• Ultrastructurally : composed of bundles of

tubular microfibrils• 11 nm in diameter

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

LASER SCAN MICROSCOPY

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

ELECTRON MICROSCOPY

• An amorphous electroluscent core • Microfibrils - electron dense fibrils of insoluble

glycoprotein complexes

• 11nm diameter

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

Amino Acids in Elastin• Composed of amino acids.

• Valine, Glycine, Alanine and Proline.

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

Secondary Structure

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

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

IMAGE OF ELASTIC FIBRES

TISSUE DISTRIBUTION

• Lungs• Elastic ligaments• Skin• Bladder• Elastic cartilage• Blood vessels

• Elastic fibres absent in : scars : keloid : dermatofibromas

• Decreased or absent in anetoderma

CLINICAL SIGNIFICANCE

• Marfan syndrome• Emphysema caused by alpha -1 anti trypsin

deficiency• Atherosclerosis• Menkes syndrome• Pseudo xanthoma elasticum• Williams syndrome

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