Repair And Regeneration PDF

REPAIR AND REGENERATION BY DR MUHAMMAD ALI SOOMRO  INTRODUCTION: Repair is the process by which lost or damaged cells are replaced by viable cells. If a cell dies the body will remove it and replace it with another functioning cell, or fill the gap with connective tis...

REPAIR AND REGENERATION BY DR MUHAMMAD ALI SOOMRO  INTRODUCTION: Repair is the process by which lost or damaged cells are replaced by viable cells. If a cell dies the body will remove it and replace it with another functioning cell, or fill the gap with connective tissue to provide structural support for the remaining cells. The motto of the repair process is to fill a gap caused by the damaged cells to regain structural continuity. Normal cells try to regenerate the damaged cells but this cannot always happen. Asexual reproduction is what repairs cells.  INTRODUCTION: To sum up, repair itself is based on two processes: – REGENERATION – REPLACEMENT  REGENERATION: The replacement of destroyed tissue by parenchymal cells of same tissue type. In other words, the replacement of destroyed cells by proliferation of near by normal cells of origin.  ABILITY TO REGENARATE: The cells are divided in to 3 types on the ability to regenerate: – 1. Labile – 2. Quiescent – 3. Permanent LABILE CELLS: QUIESCENT CELLS: PERMENANT CELLS:  CONTROL OF CELL GROWTH: Cell growth is regulated by biochemical factors produced in the local micro-environment, that can either inhibit or stimulate cell growth. Growth promotion is initiated by growth factors, while growth inhibition is done by inhibitory factors.  GROWTH FACTORS: EPIDERMAL GROWTH FACTORS. PLATELET DERIVED GROWTH FACTORS. FIBROBLAST DERIVED GROWTH FACTORS. VASCULAR ENDOTHELIAL GROWTH FACTORS. CYTOKINES I.E. IL-1 AND TNF.  INHIBITORY FACTORS: Transforming growth factors f3 Tumor necrosis factors.  REPAIR BY CONNECTIVE TISSUE REPLACEMENT: In the below stated conditions, scar formation is promoted: – When resolution fails to occur in an acute inflammation. – When parenchyma cell necrosis can not be repaired by regeneration due to: Necrotic cells are permanent cells. Stable cells are destroyed. Necrosis is so extensive that no cells are available for regeneration.  PHASES OF REPAIR BY SCAR FORMATION: PREPARATION: – The area of injury is prepared for scar formation by removal of inflammatory exudate by the lymphatics. GRANULATION TISSUE FORMATION: – Granulation tissue forms and fills the injured site, and the necrotic debris is being removed. – Granulation tissue is highly vascularized and composed of newly formed capillaries, proliferating fibroblasts and inflammatory cells.  PHASES OF REPAIR BY SCAR FORMATION: – Microscopically, it is revealed to consist of thin walled capillaries lined by endothelium and surrounded by fibroblasts. PRODUCTION OF FIBRONECTIN: – Fibronectin is a glycoprotein that plays key role in the formation of granulation tissue and is present in large amounts while wound healing. – In early stages, it is derived from plasma but later is synthesized by fibroblasts, macrophages and endothelial cells in granulation tissue.  PHASES OF REPAIR BY SCAR FORMATION: COLLAGENIZATION/ FIBROSIS: – Collagen is the major fibrillary protein of connective tissue. – Synthesized by fibroblast and is responsible for much of the tensile strength of scar tissue. SCAR MATURATION: – A recent scar consists of granulation tissue and abundant collagen along with capillaries and fibroblasts.  PHASES OF REPAIR BY SCAR FORMATION: – It appears pink on gross examination because of vascularity. – As scar matures, the amount of collagen rises and scar becomes less cellular/vascular. – Mature scar is composed of avascular, poorly cellular mass of collagen, and appears white on naked eye. CONTRACTION OF SCAR: – The final phase. – Contraction decreases size of scar and enables organ survival with maximum efficiency. THANKS THE END!