Transcript Wound Healing

Wound Healing
Junior Basic Science
1/25/2011
3 Phases of Wound Healing
• 1. Inflammation- day 1-10
• 2. Proliferation-5 days-3 weeks
• 3. Remodeling-3 weeks-1 year
Inflammation Phase: Injury
• Bleeding and vasoconstriction(5-10min),
followed by vasodilation
• Plt plug formation and clotting
• Fibrin binds the plt plug and forms the
provisional matrix (platelets+fibrin+fibronectin)
• Platelet degranulation (alpha and dense granules)
-> PDGF and TGF-B
• Chemotaxis for inflammation
Inflammation
• PMNs-almost immediately, clear debris
• Macrophages-Day 2-3 (essential)
– Fibroblast proliferation, endothelial cell proliferation
(angiogenesis), and extracellular matrix production, and they
recruit and activate additional macrophages.
• Lymphocytes
Proliferation Phase (5-21 days)
• Fibroblasts-enter provisional matrix and initiate collagen
synthesis
– Prominent cell type during this phase
• Macrophages->angiogenesis and neovascularization
• Collagen and proteoglycans or ground substance
replaces the provisional fibronectin–fibrin matrix
Remodeling Phase (3wks-1 year)
• Max collagen accumulation at 2-3 weeks. Only
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remodeling/crosslinking after 3 weeks.
Type III collagen predominates early (days 1-3),
but is replaced by type I
6 weeks-80% of final strength and 60% of
original strength
8 weeks-max tensile strength (70-80%)
Collagen
• Need alpha-ketoglutarate, vit C, O2, and iron for
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hydroxylation of proline, and crosslinking of
proline residues
Proline is every 3rd amino acid. Lysine is
abundant from hydroxylysine crosslinking
Type I, most common and most abundant in
healed wound
D-penicillamine inhibits collagen crosslinking
Surgical Wound Healing
• Primary Intention-Tensile strength is important
in healing closed incisions
– Depends on collagen deposition and cross-linking
• Secondary Intention-Epithelial integrity is
important in healing open wounds
– Dependent on granulation tissue (capillaries,
fibroblasts and collagen)
– Migration from wound edges, sweat glands and hair
follicles
Essential for wound healing
• Moist environment- optimizes epithelial migration
• Oxygen delivery- Essential
• Avoid edema- edema causes decreased O2 in
wounds
• Remove necrotic tissue- leads to infection
Factors affecting wound healing
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Nutrition-Albumin <3
Infection
Foreign body
Drugs
Diabetes
Ischemia
Aging
Radiation
Neuropathy
Scars
• Contain proteoglycans, hyaluronic acid, and
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water.
Keloids- AD, dark skinned. Collagen goes beyond
original scar
Hypertrophic scar- Collagen stays within scar
Treatment: Steroids, silicone, pressure
garments, XRT.
Infants heal with little/no scarring-multifactorial,
decreased inflammatory response, increase
hyaluronic acid?
Chronic Wounds
• Pressure Sores- pressure over bony area, occurs
when tissue pressure exceeds the capillary filling
pressure of 25 mm Hg
– Tx: Pressure off loading, debridement, myocutaneous
flap
• Leg ulcers- 90% due to venous insuff.
– Tx: Unna boot, elastic wrap
• Diabetic foot ulcers- 2nd MTP joint (Charcot’s
joint). Neuropathy leads to increased pressure->
Ischemia
– Tx: Depends on extent of ulcer
Question
• The most prominent cell type in the 1st 24
hours of a wound is :
– PMN’s
– Macrophages
– Lymphocytes
– Fibroblasts
Answer
• PMN’s
– Most abundant in 1st 24 hrs, help clear debri
Question
• The most prominent cell type day 2-4?
– PMN’s
– Macrophages
– Lymphocytes
– Platelets
Answer
• Macrophages
– Fibroblast proliferation, endothelial cell proliferation
(angiogenesis), and extracellular matrix production,
and they recruit and activate additional macrophages.
Question
• What is the most prominent cell type at 1
week?
– PMN’s
– Macrophages
– Lymphocytes
– Fibroblasts
Answer
• Fibroblasts
-Enter provisional matrix and initiate
collagen synthesis. Days 5-21.
Question
• The most predominant type of collagen in
the body?
–I
– II
– III
– IV
Answer
Type I most common, seen in skin, bone,
tendons, and healed wounds
–I
– II Cartilage
– III
– IV Basement membrane
Question
• Most abundant collagen in healing wound
during 1st 24hrs?
–I
– II
– III
– IV
Answer
• Type III- Most abundant the first 48hrs,
and is then replaced by type I.
Question
• What is the most important cell involved in
wound healing?
– PMN’s
– Macrophages
– Lymphocytes
– Fibroblasts
Answer
• Macrophages
– Essential, synthesizes cytokines and growth
factors necessary for wound healing.
Question
• Maximal tensile strength of a wound
occurs at:
–3
–6
–8
–3
weeks
weeks
weeks
months
Answer
• 8 weeks- Has 80-90% of original strength
Question
• What vitamin can you give to prevent the
negative affects on wound healing?
–A
–D
–O
–K
Answer
• Vitamin A
– 25,000 UI daily
Question
• Peripheral nerves regenerate at:
– 0.01mm/year
– 0.1mm/day
– 1mm/day
– 5mm/day
Answer
• 1mm per day
Question
• The most important factor in the healing
wounds by secondary intention is:
– Tensile strength
– Epithelial integrity
– Platelet activating factor
– cocaine
Answer
• Epithelial integrity- epithelial cells migrate
from hair follicles, wound edges and sweat
glands.
Question
• The most important factor in the healing
wound by primary intention is:
– Double cheeseburger from McDonalds
– Tensile strength
– Epithelial integrity
– Platelet activating factor
Answer
• Tensile strength, not double cheeseburger
– This is created by collagen cross linking
Question
• The dressing change regimen that will
produce maximal debridement is:
– Wet-to-dry dressing changes with saline.
– Dressing changes with Xeroflo.
– Dressing changes with silver sulfadiazine.
– Dressing changes with an occlusive dressing.
Answer
• Maximal debridement is accomplished
when the dressing is changed utilizing
wet-to-dry dressings. Enzymatic agents,
such as collagenase, may augment the
debriding effect of wet to dry dressing
changes.
Question
• Hypoxia in a wound stimulates:
– collagen synthesis
– contraction
– ovulation
– angiogenesis
– epithelialization
Answer
• Angiogenesis
Question
• Cofactors necessary for successful
hydroxylation of proline include all the
following except:
– Vitamin C.
– Magnesium.
– Ferrous ion.
– α-Ketoglutarate.
– Oxygen.
Answer
• Magnesium
Question
• Local factors which invite wound infection
include all of the following except:
– Foreign material.
– Radiation injury.
– Poor circulation.
– Disruption of fascia.
– Hematoma.
Answer
• Disruption of fascia
– Depth of injury into the fascia has not been
identified as a wound characteristic that
predisposes to infection
Question
• Significant collagen synthesis first begins
in a wound at:
– 2 to 4 weeks.
– 7 to 10 days.
– 0 to 12 hours.
– 12 to 24 hours.
– 3 to 5 days.
Answer
• Significant collagen synthesis begins in a
wound at 3 to 5 days.