wound healing repair + regeneration repair + regeneration new epithelium growth new epithelium...

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WOUND HEALING WOUND HEALING REPAIR + REGENERATION REPAIR + REGENERATION NEW EPITHELIUM GROWTH NEW EPITHELIUM GROWTH

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WOUND HEALINGWOUND HEALING

REPAIR + REGENERATIONREPAIR + REGENERATION

NEW EPITHELIUM GROWTHNEW EPITHELIUM GROWTH

TISSUE REPAIRTISSUE REPAIR

Replacement of injured or dead Replacement of injured or dead cells is critical to survival.cells is critical to survival.

Repair involves mainly two Repair involves mainly two processesprocesses

1.1. RegenerationRegeneration

2.2. Replacement by connective tissue Replacement by connective tissue or fibroplasia.or fibroplasia.

Wound healingWound healing is an intricate process is an intricate process where the skin (or another organ-tissue) where the skin (or another organ-tissue) repairs itself after injury. In normal skin, repairs itself after injury. In normal skin, the the epidermis and and dermis exist in a exist in a steady-state equilibrium, forming a steady-state equilibrium, forming a protective barrier against the external protective barrier against the external environment. Once the protective barrier environment. Once the protective barrier is broken, the normal (physiologic) is broken, the normal (physiologic) process of wound healing is immediately process of wound healing is immediately set in motion.set in motion.

Steps in wound healingSteps in wound healing

wound healing is divided into three or wound healing is divided into three or four sequential phases: (1) four sequential phases: (1) hemostasis (not considered a phase by some authors)(not considered a phase by some authors)

, (2) inflammation, (2) inflammation , (3) proliferation and, (3) proliferation and (4) remodeling.(4) remodeling. Upon injury to the skin, a set of complex Upon injury to the skin, a set of complex

biochemical events takes place to repair biochemical events takes place to repair the damage.the damage.

Cells are divided into three types Cells are divided into three types based on their proliferative based on their proliferative capacity:capacity:

1.1. Labile cellsLabile cells

2.2. Stable cellsStable cells

3.3. Permanent cellsPermanent cells

Labile cells: Labile cells: – This sub-population of cells is constantly turned over. The This sub-population of cells is constantly turned over. The

best examples are found in the epithelial cell population of best examples are found in the epithelial cell population of the the skinskin or or gutgut, and the hematopoetic cells in the , and the hematopoetic cells in the bone bone marrowmarrow. These cells have a short, finite life span, die via . These cells have a short, finite life span, die via apoptosis, and are rapidly replaced.apoptosis, and are rapidly replaced.

Permanent cells: Permanent cells: – Permanent cells are found in the CNS (Permanent cells are found in the CNS (neuronsneurons) and heart ) and heart

((Cardiac muscleCardiac muscle). Once they are destroyed, they cannot ). Once they are destroyed, they cannot regenerate. regenerate.

Stable cells characteristically Stable cells characteristically undergo few divisions. These cells undergo few divisions. These cells are capable of regeneration following are capable of regeneration following injury.injury.

Includes hepatocytes, renal tubular Includes hepatocytes, renal tubular cells, parenchymal cells of many cells, parenchymal cells of many glands and numerous mesenchymal glands and numerous mesenchymal cells( sm, endo. CT,cartilage, cells( sm, endo. CT,cartilage, osteoblasts)osteoblasts)

CLINICAL SURGICAL CORRELATES CLINICAL SURGICAL CORRELATES

OF WOUND HEALINGOF WOUND HEALING PRIMARY UNIONPRIMARY UNION HEALING BY “FIRST HEALING BY “FIRST

INTENTION”INTENTION” SUTURED SUTURED

SURGICAL SURGICAL INCISIONINCISION

SECONDARY UNIONSECONDARY UNION HEALING BY HEALING BY

“SECONDARY “SECONDARY INTENTION”INTENTION”

LARGE DEFECTS, LARGE DEFECTS, ULCERSULCERS

W.B. Saunders Company items and W.B. Saunders Company items and derived items Copyright (c) 1999 derived items Copyright (c) 1999

by W.B. Saunders Companyby W.B. Saunders CompanySlide 4.17

WOUND CONTRACTION IN A WOUND CONTRACTION IN A CENTRIPETALCENTRIPETAL FASHIONFASHION

WOUND CONTRACTION BY ACTION OF MYOFIBROBLASTS

WOUND CONTRACTION

First 24 hrs; First 24 hrs; Neutrophils’ migration towards fibrin clot.Neutrophils’ migration towards fibrin clot. ACUTE INFLAMMATORY RESPONSEACUTE INFLAMMATORY RESPONSE ERYTHEMA, EDEMAERYTHEMA, EDEMA Basal cells exhibit mitotic activityBasal cells exhibit mitotic activity

24-48 hrs:24-48 hrs: Epithelial cell from edges migrate and Epithelial cell from edges migrate and

proliferate along dermis.proliferate along dermis. PLATELET/FIBRIN COVERINGPLATELET/FIBRIN COVERING MIGRATION TO MIDLINEMIGRATION TO MIDLINE

WOUND HEALING WOUND HEALING SEQUENCESEQUENCE

Day 3:Day 3: Neutrophils replaced by Neutrophils replaced by

macrophages and macrophages and granulation tissue granulation tissue INVADES WOUND SPACEINVADES WOUND SPACE

Collagen fibres formation.Collagen fibres formation. CONTINUED EPITHELIAL CONTINUED EPITHELIAL

THICKENINGTHICKENING

Day 5:Day 5: Neovasularization.Neovasularization. Bridging of incision by Bridging of incision by

collagen fibrescollagen fibres MAXIMAL ANGIOGENESIS MAXIMAL ANGIOGENESIS

AND GRANULATION AND GRANULATION TISSUETISSUE

EPITHELIUM RESTOREDEPITHELIUM RESTORED

Second week:Second week: Continue collagen Continue collagen

deposition and fibroblast deposition and fibroblast proliferation.proliferation.

““BLANCHING”BLANCHING” DECREASED VESSELS, DECREASED VESSELS,

EDEMAEDEMA RESOLUTION OF RESOLUTION OF

INFLAMMTORY INFLAMMTORY INFILTRATEINFILTRATE

After one month:After one month: Scar tissue without Scar tissue without

inflammatory cells.inflammatory cells. CELLULAR CONNECTIVE CELLULAR CONNECTIVE

TISSUETISSUE PROGRESSIVE INCREASE OF PROGRESSIVE INCREASE OF

TENSILE STRENGH OVER TENSILE STRENGH OVER NEXT SEVERAL MONTHSNEXT SEVERAL MONTHS

Remodeling phaseRemodeling phase

3 week to 2 year3 week to 2 year New collagen forms which increase New collagen forms which increase

tensile strength to woundtensile strength to wound Balance of matrix degradation and Balance of matrix degradation and

collagen synthesiscollagen synthesis Scar tissue is only 80% as srtong as Scar tissue is only 80% as srtong as

original tissue.original tissue.

HYPERTROPHIC SCARHYPERTROPHIC SCAR

linear, red, RAISED,PRURITIC linear, red, RAISED,PRURITIC LESIONS,LESIONS,

confined to the original injury siteconfined to the original injury site

Common affect under constant Common affect under constant pressure and stretching area. pressure and stretching area.

Usually arise within one month of Usually arise within one month of injuryinjury

CAUSES OF HYPERTROPHIC CAUSES OF HYPERTROPHIC SCARSCAR

FOREIGN BODY IN THE WOUNDFOREIGN BODY IN THE WOUND SCRATCHINGSCRATCHING HEMATOMAHEMATOMA SECONDARY INTENTIONSECONDARY INTENTION EXCESSIVE TENSIONEXCESSIVE TENSION INADEQUATE WOUND CLOSUREINADEQUATE WOUND CLOSURE

KELOIDSKELOIDS

Form, irregularly shapeForm, irregularly shape Thin epi. Caused by surgical procedure, Thin epi. Caused by surgical procedure,

burn, trauma, inflamm.burn, trauma, inflamm. Spread beyond the limit of original Spread beyond the limit of original

injuryinjury Appear within week or yr. Appear within week or yr. LOCALLY INVASIVE BENIGN NEOPLASTIC LOCALLY INVASIVE BENIGN NEOPLASTIC

TISSUETISSUE Persist over time.RARELY REGRESSPersist over time.RARELY REGRESS

Early lesion: red, tender, rubbery, Early lesion: red, tender, rubbery, may be telangiectaticmay be telangiectatic

Old lesion: brown, pruritic, pain, Old lesion: brown, pruritic, pain, hyperesthesiahyperesthesia

Varying in size and numberVarying in size and number Most commo0n in neck, chest, ear, Most commo0n in neck, chest, ear,

extremitiesextremities Rarely on face, palm, soleRarely on face, palm, sole

Complications of wound healingComplications of wound healing

- - Deficient scar formation-which can lead to Deficient scar formation-which can lead to rupture of the wound due to inadequate rupture of the wound due to inadequate formation –result in dehiscence and formation –result in dehiscence and ulcerationulceration

- Excessive scar formation of the repair Excessive scar formation of the repair components- components- KeloidKeloid & hypertrophic scar & hypertrophic scar

W.B. Saunders Company items and W.B. Saunders Company items and derived items Copyright (c) 1999 derived items Copyright (c) 1999

by W.B. Saunders Companyby W.B. Saunders Company

SUMMARY WOUND HEALING