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.
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
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
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