Tissue repair ,Regeneration & sheadling

 Tissue repair ,Regeneration & shealing :-

·         Tissue repair is also called tissue healing

·         Our body response against injury and its attempt to restore structure & function by living tissue.

·         By the two process injured tissue are replacing there are –

(1)   Regeneration

(2)   Repair

 

 

 

 

 

 

 

 

 

 

(1)Regeneration:-

* Some tissue are able to replace the damaged components and essentially return to normal state this process is called Regeneration .

*  regeneration occurs by proliferation of cells that survive the injury& retain the capacity to proliferation.

* Depending upon their capacity to divide the cells of the body can be devided into three groups.

(1) Labile cells

(2) stable cells

(3) permanent cells

 

(2)Repair:-

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Cell cycle.                                                                       growth

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                      Parent cell                                              reproduction

 

 

Cell repair:-

·         Repair is the replacement of injured tissue by fibous tissue.

·         Process of repair perform by two ways.

(1)   Granulation tissue formation

(2)   Wound contraction & strength.

 

(1) Granulation tissue formation:-

·         Granulation tissue are the hallmark of tissue repair

·         Granulation name is because of granules apperence on the surface of wound.

·         It appearance in pink soft granular in form

·         Granulation tissue is not a granuloma both are very different.

·         Granulation tissue is the focai of granulomatous inflammation.

·         Process of the granulation tissue formation can be devided into four phases.

(1)   Bleeding phase

(2)   Inflammation phase

(3)   Proliferation phase

(4)   Remodelling phase

 

(1) Bleeding phase :-

Bleeding may stop after few hours(4-6 hrs.) but it may vary ,following by clotting of blood at the site of injury.

(2) Inflammation phase:-

·         Inflammation is the essential component of healing process.

·         The enzymes release from neutrophils as well as autolytic enzymes release from the dyeing cells.

·         In the inflammatory phase neutrophils and monocytes are the predominant cells then there is the phase is clearance phase .

·         After the clotting ,fibrin & fibronectin remain in the tissue which form the substance3 for adhesion of various inflammatory cells.

 

(3) Proliferation phase:-

It consist of two main process-

(1)   Angiogenesis

(2)   Fibrogenesis

 

(1)Angiogenesis:-

* formation of new blood vessels at the site of injury taken place by proliferation of endothelial cells from the margin of several blood vessels.

* initially ,the proliferated endothelial cells are solids buds but with in afew hours develop a lumen & start carrying blood.

* The newly formed blood vessels are more leaky accounting for the oedematous appearance of new granulation tissue soon ;there blood vessels differentiate into muscular arterioler thin walled venules & tree capillaries.

* The process of angiogenesis is stimulated with proteolytic destruction of basement membrane

*Angiogenesis taken place under the influence of following factors.

 

(a)   VEGF(vascular endothelial growth factor) elaborated by mesenchymal cells while its receptors are present in endothelial cell only.

(b)   POGF – platelets derived growth factors,

(c)    PGF – polypeptide growth factor,

(d)   EGF – epidermal growth factors

(e)   ECM  (extracellular or matrix ) – collegen glycol ptn., proteoglycon .

 

(2)Fibrogenesis:-

* The newly formed blood vessels are present in an amorphous ground substance or matrix.

* The new fibroblast have feature intermediate b/w there of fibroblast & smooth muscles cells (myofibroblast).

* Collagen fibrils begin to appear by about 6thday .

*The myofibroblast have surface receptors for fibronectin molecules which forms bridge between collagen fibrils .

* As maturation proceeds , more and vmore collagen is formed while the member of active fibroblasts and new blood vessels decrease .

* this results in formation of inactive  looking scar this process is called cicatrisation.

 

Remodeling:-

·         The connective tissue that has been deposited by fibroblast is reorganized to produce the stable fibrous scar.

·         This process begin 2-3 weeks after injury and may continue for month or years.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Wound contraction & strength:-

·         Wound start contracting after 2-3 days and process is completed by the 14 th day.

·         During this period ,the wound is reduced by approximately 80% of its original size.

·         The wound is strengthened by proliferation of fibroblast and myofibroblast which get structural support from the extra cellular matrix.(ECM)