Fundamentals Flashcards
What are the phases and timings of wound healing?
Inflammatory (days 1-6)
Fibroproliferative (Day 4 - week 3)
Maturation/remodelling (week 3 - 1 year)
What phase of wound healing 2 weeks post injury?
Fibroproliferative
Outline the stages of the inflammatory phase of wound healing
Vasoconstriction, coagulation, vasodilation and increased vascular permeability, chemotaxis, cell migration
Outline the stages of cellular migration during the inflammatory phase of wound healing
Margination, diapedesis, fibrin deposition
What is the predominate cell type within a wound during the first 48h
Neutrophils (24-48h)
What is the predominate cell type within a wound during 48-96 hours?
Macrophages (48-96 hours; 2 days - 2 weeks)
Which cell type is most critical for wound healing?
Macrophages
What are the hallmark features of a chronic wound?
Failure of a wound to progress from the inflammatory to the fibroproliferative phase, resulting in prolonged and unresolved inflammation
What is the role of debridement in the setting of chronic wounds?
Remove inflammatory mediators and senescent cells to turn a chronic wound into an acute wound to reset the wound healing process
Outline the stages of the fibroproliferative phase of wound healing
Matrix formation, angiogenesis, epithelisation
What is the dominant cell type within a wound one week following an injury?
Fibroblasts
When are fibroblasts present in a wound post-injury?
Day 2-3
Outline tor production of glycosaminoglycan
Hyaluronic acid > chondroitin-4-sulfate, dermatan sulfate, heparin sulfate > collagen
What is the difference between angiogenesis and vasculogenesis?
Angiogenesis = formation of new blood vessels from existing ones
Vasculogenesis = formation of new blood vessels de novo
Outline the remodelling phase of wound healing
Week 3 to 1 year
Equilibrium in collagen synthesis and breakdown
Type I collagen replaces type III collagen
Decrease in GAGs, water content, vascularity and cellular population
What is the tensile strength of a wound at 1 week?
3%
What is the tensile strength of a wound at 3 weeks?
30%
What is the tensile strength of a wound at 3 months?
80%
What is the normal ratio of type I to III collagen?
4:1
Type I collagen
90%
Skin, bone and tendon
Type II collagen
Cornea
Hyaline cartilage
Type III collagen
Vessel and bowel walls
Uterus
Skin
Type IV collagen
Basement membrane
Where are multipotent epithelial progenitor cells found?
Bulge stem cells in hair follicle
Outline the stages of epithelisation
Mobilisation (loss of contact inhibiton), migration (contact inhibition re-established), mitosis, differentiation
What cell type is implicated in Dupuytren’s?
Myofibroblasts
Mutation in which gene is found in Ehlers-Danlos?
COL5A1
COL5A2
COL1A1
Mutation in which gene is found in progeria?
LMNA
Outline features of progeria
limited growth, full body alopecia, beaked nose, atherosclerosis
Mutation of which gene found in Werner
WRN
Pseudoxanthoma elasticum
Cutis laxa
How does vitamin A deficency effect wound healing?
Supplementation reverses delayed wound healing from steroids
How is vitamin C involved in wound healing?
Vital for hydroxylation of amino acids essential for collagen synthesis
What factors affect wound healing?
Systemic: co-morbidities, drugs (steroids), smoking, vitamin deficiencies and nutrition
Local: Oxygen delivery, infection, biofilm, radiation,
What is a hypertrophic scar?
Elevated scar within borders of original scar. Composed of type III collagen orientated parallel to epidermal surface with abundant myofibroblasts. develop 1-2 months post injury.
What is a keloid scar?
Elevated scar outside borders of original scar. Disorganised type I and III collagen bundles. Form weeks-years post injury.
When is peak tensile strength of a wound?
41-60 days post injury (80% of original strength)
How can methylene blue be used to aid surgical debridement of chronic wounds?
Applied on induction, wound wiped clean. Stains eschar, granulation and necrotic tissue thus identifying tissue to be debrided
Outline the strength and resorption times of absorbable sutures (VR, monocryl, PDS)
What are antimicrobial sutures coated in?
Triclosan
Blocks bacterial fatty acid synthesis
