Wound healing Flashcards
What are the four main stages of wound healing?
Haemostasis, inflammatory, proliferative, remodelling
Function of macrophage in wound healing
Proliferates during inflammatory stage
Function of fibroblasts in wound healing
Provides supportive ‘scaffolding’
Function of neutrophils in wound healing
Clear away bacteria
Function of platelets in wound healing
Clot
Function of endothelial cells in wound healing
Revascularise an area with new blood cells
Function of fibrin in wound healing
Binds to form clot
How long does haemostasis take to occur?
Within seconds to hours after accident
Process of haemostasis
Forms fibrin clot so blood doesn’t leak from wound
Vessels rupture, causing platelet aggregation, vasoconstriction and activating the coagulation cascade
Process of inflammation
- Cytokines activate vasodilation and attract/activate immune cells to area
- Neutrophils phagocytose bacteria and debris, not important unless wound contaminated
- Macrophages are a source of stimulatory signals and are important for wound healing, phagocytose debris
How quickly does inflammation occur?
Hours to days
Examples of wound complications
Infection
Adhesion
Keloid (excessive car formation)
Would dehiscence (deficient healing)
Ways to heal wound
Sutures/steri-strips Hyperbaric oxygen chamber Manuka honey Maggots Wound vac
Systematic factors impairing wound healing
Malnutrition Obesity Disease Immunodeficiency Smoking Stress Steroids Old age
Local factors impairing wound healing
Pressure Dehydration Trauma Oedema Infection Necrosis
How quickly does remodelling occur?
Between 3 weeks and a year
Process of wound remodelling
- Changes collagen composition over time (type iii to type i)
- Collagen better aligned
- New blood vessels no longer required so removed by apoptosis
- Fibrous scar formed by collagen cross linking increases fibre size
Is scar tissue as strong as normal tissue?
No - about 80% as strong
What is fibroplasia?
Fibroblasts migrate into wound and are activated by macrophages to replicate, with the dominant cells at the wound edge. They synthesise and deposit collagen and proteoglycans (to hold granulation tissue together)
What is epithelialisation?
Epidermal covering reconstituted from wound margin and hair follicle remnants. The keratinocytes migrate across the wound and the neodermis differentiates and stratifies
How does contraction occur to pull a wound together?
Fibroblasts differentiate to myofibroblasts that produce contractile proteins to pull the wound edges together
Process of proliferation
- Takes days to weeks
- Angiogenesis
- Oxygen required for fibroblasts to make collagen to establish granulation tissue
- Supply of oxygen transported by blood vessels
- New vascularisation is required
- Macrophages and keratinocytes provide angiogenic stimuli
- Start as endothelial cells budding from existing vessels
- Sprout towards wound following oxygen gradient
- Immature vessels differentiate into capillaries/arterioles/venules
- Fibroplasia
- Matrix deposition depends on oxygen and substrate availability and growth factors
- Epithelialisation
- The new epidermal layer is weak as the dermal layer below isn’t yet regenerated
- Contraction: fibroblasts differentiate to myofibroblasts that produce contractile proteins to pull the wound edges together
What is a primary wound?
Can be surgical openings
Smooth borders, edges close in vicinity
What is a secondary wound?
Large tissue loss, e.g. dog bites
Primary closure not possible
