Wound Healing Flashcards
What are the four stages of wound healing?
– Haemostasis
– Inflammation
– Proliferation
– Remodelling
What is haemostasis?
(1) Vasoconstriction of a broken vessel reduces bleeding.
(2) A platelet plug forms as platelets adhere to exposed collagen fibres of
the vessel wall. The platelet plug temporarily seals the break.
(3) A blood clot forms as platelets become enmeshed in fibrin threads.
This forms a longer-lasting seal and gives the vessel a chance to repair itself.
What is inflammation phase of wound healing?
1) bacteria and other pathogens enter wound
2) platelets from blood release blood clotting proteins at wound site
3) mast cells secrete factors that mediate vasodilation and vascular constriction.
Delivery of blood, plasma and cells to injured areas increases
4) neutrophils secrete factors that kill and degrade pathogens
5) neutrophils ad macrophages removes pathogens by phagocytosis
6) macrophages secrete hormones (cytokines) that attract immune system cells to the site and activat cells involves in tissue repair
7) inflammatory response continues until the foreign material is eliminated and the wound is repaired
What is the proliferation phase of wound healing?
1) new ECM production
2) cell proliferation
3) angiogenesis
4) macrophages remove apoptotic neutrophils
growth factors involved (VEGF, EGF, FGF and TGF-beta
What is the remodelling phase of wound healing?
1) remodelling off newly deposited ECM
2) MMPs and TIMPs
3) scar tissue forms
4) if inflammation persists formation of fibrosis/hypertrophic scars
What is the foreign body response?
Response to non-degradable synthetic
biomaterials and metallic components.
What is the process of the foreign body response?
– Blood material interaction – Deposition of protein film – Provisional matrix formation – Acute inflammation – Chronic inflammation – Granulation tissue formation – Foreign body reaction/fibrosis – Capsule development
When does foreign body response occur?
Anything implanted into the body will elicit
some response from the host.
• Dependent on material, cells, anatomical
location, topography, growth factors, bioactive
molecules etc.
• Overlap between beneficial wound healing
processes and FBR, therefore hard to prevent.
What is the effect of prolonged macrophage response?
negative effects on tissue engineered grafts. can also be positive and can promote remodelling and integration of implanted constructs.
In macrophage response, what effects must be balanced?
Macrophages cause chronic inflammation and foreign body response Macrophages promote remodelling of implant construct
What are the different types of macrophages?
M1
M2
What is the M1 macrophage?
pro-inflammatory
destroys pathogen
remove debris from wound site
(leads to scarring and FBR)
What is the M2 macrophage?
anti-inflammatory
haemostatic
promotes wound healing
(beneficial for TE
What is immunosuppression?
to stop rejection of allogenic (or xenogenic) graft or cells immunosuppressant can be used
- patients must use immunosuppressant drugs for life
What are the risks associated with non specific immunosuppressant drugs?
infection
malignancy
