teori - wound healing

8/12/2019 TEORI - Wound Healing

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Wound Healing

Ferry Senjaya


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DefinitionWound healing is the response to acute or chronic injury, a

process by which a damaged tissue is restored, as closely

as possible, to its normal state


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Phases of Wound Healing1. Inflammatory

2. Proliferative

3. Remodelling


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Inflammatory Phase (1) Begin at the time of injury ; lasts 2-3 days

Begin with vasoconstriction

Platelet plug forms & clotting cascade activated

fibrin deposition

Platelets release PDGF & TGF-, attracting

inflammatory cells


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Inflammatory Phase (2)After hemostasis achieved, vasodilation occurs &

vascular permeability increases, aiding infiltration of

inflammatory cells into the wound

Neutrophils peak at 24 hours debridement Monocytes macrophages (peak within 2-3 days)

Macrophages produce PDGF & TGF-, attracting

fibroblast collagen production


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Proliferative Phase Begin around day 3, as fibroblast arrive ; lasts through

week 3

Fibroblast : attracted & activated by PDGF & TGF-

Collagen synthesis (mainly type III), angiogenesis, &epithelialization occur

Total collagen content increases for 3 weeks, until

collagen production & breaksown become equal remodelling phase begins


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Remodelling Phase Increased collagen production & breakdown continue for

6 months to 1 year

Type I collagen replaces type III until it reaches 4:1 ratio

of type I to type III Wound strength increases as collagen reorganizes along

lines of tension & is cross-linked

Vascularity decreases Fibroblast & myofibroblasts cause wound contraction


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Phases of Wound Healing


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Mechanical Properties Wounds have little strength during the first 2-3 weeks

(inflammatory & proliferative phase)

By the third week, the wound begin to gain strength

rapidly as remodelling occurs Wound have 50% of their final strength at 6 weeks, &

most of their final strength a few weeks later

Strength may continue to slowly increase until 6 to 12months fron the time of injury

Max strength is about 75% of normal tissue


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Healing in Specific Tissues : Skin In addition to production of connective tissue & wound

contraction, epithelialization occurs

A single layer of cells advances from the wound edges (&

adnexal structures in partial thickness wounds), thenstratifies

If epithelialization is prolonged as in healing by

secondary intention or in the deep partial-thickness

wound or burn, the inflammatory phase lasts longer,

resulting in increased collagen production & contraction


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Healing in Specific Tissues : Bone (1) The fracture site undergoes inflammatory phase

Osteoinduction : precursor cells in the endosteum,

periosteum, & surrounding tissue become osteoblasts

Osteoconduction : osteoblasts enter the fracture site

A callus then forms, containing fibroblasts, osteoblasts,

& other cells

Chondroblasts produce ground substance, fibroblasts

produce collagen, osteoblasts produce hydroxyapatite


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Healing in Specific Tissues : Bone (2) Both apposition of bone & endochondral ossification

occur

At first the callus consists of poorly organized woven

bone, which is remodeled by osteoclasts & osteoblasts intolamellar bone

The more rigidly fixed & well reduced the fracture is, theless prominent the callus formation & endochondral

ossification are ; healing mainly occur by apposition Once remodeling is finished, the healed bone structure is

the same as normal bone, with no remaining scar


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Healing in Specific Tissues : Tendon (1) Tendon heals by combination of 2 mechanisms : intrinsic

& extrinsic healing

Intrinsic healing :

The inflammatory phase is minimal Epitenon cells move to the site of injury, producing

collagen, acting like fibroblasts

Intrinsic healing is increased by tendon motion


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Healing in Specific Tissues : Tendon (2) Extrinsic healing :

Inflammatory, proliferative, & remodelling phases occur

After hemostasis, inflammatory cells infiltrate the wound

Fibroblasts are attracted & produce collage, which iseventually remodelled

Adhesions forms between the site of injury & surrounding

tissues, & acts as pathway for cell migration &

revascularization

Adhesions, & therefore extrinsic healing, are increased by

immobilization


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Healing in Specific Tissues : NerveAxons distal to the injury are phagocytized by

macrophages & Schwann cells (Wallerian degeneration)

The proximal axons each produce one or more myelinated

regenerating fibers with growth cones at the distal end ofeach fiber (regenerating units)

The regenerating units grows distally, directed by

chemical factors


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Healing in Specific Tissues : Liver The liver is the only adult organ that undergoes

regeneration

All hepatic cells, are involved in recreating normal

heopatic histology without scar formation Scarring (cirrhosis) occurs with chronic or severe damage


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Types of Wound Healing Primary union / healing by first intention

Secondary union / healing by second intention


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Wound Closure1. Primary closure

2. Delayed primary closure

3. Secondary closure


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Primary Closure Wound closed surgically soon after creation


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Delayed Primary Closure Wound remains open for afew day before surgical closure

Decrease the risk of infection in contaminated wounds


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Secondary Closure Wound closes over time by contraction

Appropriate for infected or contaminated wounds

Allows drainage of fluid

Allows debridement with dressing changes

Prolonged inflamatory phase, leading to increased

scarring & wound contracture


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teori - wound healing

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