Vascular response
- Initial vasoconstriction as a direct response to trauma
- Exposed subendothelial tissue activates coagulation and complement cascades
- Platelet adhesion and aggregation causes clot formation
- Degranulation of platelets releases growth factors and chemotactic factors
- Inflammatory response due to histamine and 5HT release produces:
- Vasodilatation
- Increased capillary permeability
- Margination of neutrophils
Cellular response
- Migration of neutrophils, macrophages and lymphocytes
- Macrophages produce growth factors leading to migration of fibroblast and epithelial cells.
- This causes cellular proliferation with three components:
- Epithelialisation
- Contraction
- Fibroplasia
- Epithelial barrier important to prevent infection and maintain fluid balance
- Achieved by both migration and proliferation of epithelial cells
- Migration require presence of granulation tissue
- When epithelial cover complete contact inhibition prevents further epithelial growth
- Contraction can account for up to 80% reduction in wound size
- Contraction due to myofibroblasts in granulation tissue
- Usually more marked in animals than in man
- Fibroplasia due to procollagen production by fibroblasts
- Intra and intermolecular bonds form the Collagen fibres with triple helical quaternary structure
- Extracellular matrix contains Fibronectin and Glycosaminoaglycans
- Regulates collagen synthesis and cellular differentiation
- Accompanied by simultaneous angiogenesis
- Proliferation is followed by remodeling
- Maximum collagen production occurs at 20 days
- Maximum wound strength at 3 to 6 months
- Initial collagen production disorganised
- Remodelling lines it up with stresses in skin
- Reduced vascularity and cellularity
Important growth factors
- Platelet Derived Growth Factors (PDGF)
- Insulin Like Growth Factor (IGF-1)
- Epidermal Growth Factor (EGF)
- Transforming Growth Factor (TGFß)
Factors influencing wound healing
- Systemic factors
-
Age and Sex
- Nutrition
- Vitamin and trace element deficiencies - vitamin C,
vitamin A, zinc
- Drugs – steroids, chemotherapy, immunosuppression
- Systemic disease – diabetes, jaundice, malignancy
- Hypoxia
- Local Factors
- Blood Supply
- Infection
- Foreign Bodies
- Surgical Technique
Bibliography
Appleton G V N. Leaper D J.
The Infected Wound. Hospital Update 1992; 189 -198.
Herroeder S, Durieux M E, Hollman M W. Inflammatory responses after surgery. Hosp
Med 2002; 63: 99-103
Wilmhurst A D. Wound healing and the plastic surgeon.
In: Johnson C D Taylor I eds. Recent Advances in Surgery
19. Edinburgh. Churchill
Livingston. 1996: 169 -182.
Witte M B, Barbul A. General
principles of wound healing. Surg Clin N Am 1997; 77: 509
– 528. |