Cutaneous Wound Healing Flashcards
(22 cards)
Name some areas of constant regeneration
Liver, Kidney, Haematopoietic, Skin, GIT
What is needed for regeneration?
- Stem cells intact
2. CT framework intact
Describe stages in healing
- Inflammatory response - removal of dead + damaged tissue
- Prolif + migration of neutrophils, macrophages, skin cells, fibroblasts
- Angiogenesis - capillary sprouting + recruiting EPC’s
- Collagen deposition
- Tissue remodelling, wound contraction + strengthening
What is the role of macrophages in wound healing?
- remove wound debris by. phagocytosis
- produce collagenase + elastase
- produce NO + ROS = antimicrobial
- cause chemotaxis + prolif of fibroblasts + keratinocytes by release GF
- release VEGF for angiogenesis
- aid in deposition + remodelling of ECM
What factors influence wound healing?
- tissue enviro + extent of tissue damage
- intensity + duration of stimulus
- foreign bodies + inadequate blood supply
- diabetes, steroids (inhibit)
What is angiogenesis/neovascularisation?
- branching + extension of adjacent blood vessels
- recruitment of endothelial progenitor cells from bone marrow -> form new BV’s
Describe wound healing by second intention
- For wounds with separated edges
- Healing by granulation
- Slower, broader scar
- Wound contraction
- Risk of infection
- Regular cleaning required
Describe healing by first intention
- For wounds with opposed edges
- Wound edges Brough together
- Epithelialisation
- Minimal scarring
How is second intention wound healing different from first?
- more extensive inflammatory reaction
- more granulation tissue
- wound contraction + substantial scar formation - some of the fibroblasts develop ability to contract = myofibroblasts
What systemic factors influence wound healing?
- nutrition
- metabolic status
- circulatory status
- hormones
What are the complications in cutaneous wound healing?
- deficient scar formation
- excessive formation repair components
- excessive contraction
- calcification, pigmentation, pain
- incisional hernia
What triggers the extrinsic and intrinsic clotting pathways and what happens next?
Extrinsic = triggered by tissue damage
Intrinsic = triggered by exposed collagen
End product = prothrombinase (Xa) = breaks down prothrombin -> thrombin = converts fribinogen -> fibrin
What does the binding of thrombin to protease activated receptors cause?
- P selection mobilisation
- Chemokine production
- Endothelial adhesion molecule expression
- COX2 induction
- PG.PAF.NO production
All = involves in wound healing + inflammation
When are neutrophils replaced by macrophages?
48-96 hours
Describe the timeline for recovery of tensile strength
- 10% by end of week 1
- 20-80% 3 month plateau
- Initial excess collagen synthesis
What is the effect of old age on wound healing?
- reduced inflam response
- delayed angiogenesis
- reduced collagen synthesis, degradation
- slower epithelialisation
What is the effect of diabetes on wound healing?
- ulcers/neuropathy = unable to sense + relieve cutaneous pressure
- ischaemia secondary to vascular disease
- prone to infection - impaired granulocyte function + chemotaxis
- prolonged inflammation
- impaired neovascularisation
- decreased collagen synthesis
- increased levels of proteinases - inactivate haemostat system
- defective macrophage function
Describe fatal wound healing
- re-epithelialize rapidly
- heal without scarring - TGFB1
- skin rich in metalloproteinases
What is a hypertrophic scar?
- rapid growth
- regress
- Myofibroblasts
- Collagen fibres parallel to skin surface
- Vertically orientated blood vessels
What is a keloid scar?
- constant growth
- no spontaneous regression
- extent beyond margins of tissue damage
- genetic predisposition
- thick, haphazardly orientated collagen bundles
How are wound infections classified?
- Contamination - organisms in wound
- Colonisation - replicating organisms in wound without inflam. response
- Local infection/critical colonisation - organism + tissue response
- Spreading invasive infection - organisms + inflammation + spread
What is a biofilm?
- fibrin, thrombin, albumin, collagen, bacteria
- risk factor for infection
- no blood supply so cannot be treated with antibiotics
