Wound Healing L05 Flashcards
If the extracellular matrix is intact then ………… can proceed.
If however the architecture is disrupted then a repair process by ………. will occur.
1) regeneration
2) scarring
What is the extracellular matrix made up of
Components:
1) basement membrane
2) interstitial matrix
Functions of extracellular matrix
Mechanical support & anchorage for cell migration
Control cell growth through Integrin cellular Receptors
Maintain cell differentiation – Again Integrin Receptors
Scaffold for Tissue Renewal – IF the basement membrane is damaged then you will get scar formation.
Storage & Regulation of Cytokines for rapid deployment (ie Epidermal Growth Factor; EGF, fibroblast growth factor; FGF)
How does ECM transduct a signal
Integrins binds ECM components.
These integrins interact with the cellular cytoskeleton. This can produce intracellular signals.
Damage to ECM can induce a cellular response in wound repair. (Specifically bFGF)
Use of monocytes during the acute inflammatory response
Monocytes migrate into the tissue at the site of injury and mature into macrophages
First step of the Wound healing process
1) Heamostasis
Purpose – Form a clot, seal the wound. Prevent blood loss and prevent infection.
Whats the first stage of the proliferative phase
1) Angiogensis- Growth of new blood vessels from existing ones. Macrophages secrete a screte a growth factor that stimulates angiogenesis (VEGF) and induce vascular endothelial cells to proliferate. They can also secrete little collagenase to degrade the basement membrane around surviving vessels to allow capillary buds to form.
Explain what happens in the maturation phase
Myofibroblasts have contractile properties and pull the edges of the original wound together. Collagen is remodelled during contraction and more is deposited (collagen I) to maintain new architecture.
Process of scar maturation occurs after 3 weeks from acute inflammation and can take months/years to fully progress. It increases the strength of the collagen through cross linking. The capillary network matures and theres decreased proteoglycan content (this reduces water and oedema content)
What are some of the local factors involved in delayed healing
1) Infection
2) Mechanical factors such as movements that may compress blood vessels and separate the edges of the wound
3) Foreign bodies such as bone fragments or glass shards
What are some of the systemic factors involved in delayed healing
1) Nutrition (protein/ vitamin C deficiency)
2) Metabolic status (diabetes microangiopathy may cause delayed healing)
3) Circulatory status e.g Arteriosclerosis (inadequate blood supply) or varicose veins (retarded venous drainage)
What are the three categories of complications in wound healing
- Inadequate formation of granulation tissue or assembly of a scar
- Excessive formation of the components of the repair process – hypertrophic (burnt skin like scars) and keloid (little growth spurts like) scars
- Formation of contractures and loss of function (excessive wound contraction can cause permanent damage to mobility)
What is the basement membrane and interstitial matrix made up of
- Collagen
- Type I – bone, tendon, scars
- Type III – tissue scaffold/ interstitial matrix
- Type IV – basement membranes
- Elastin
- Glycoproteins,
- Proteoglycans
Second step of the wound healing process
2) Inflammatory /reactive phase
Purpose – A clot is induced to seal wound. Inflammatory cells stimulate local tissues to respond at the site of injury. Macrophages release cytokines such as VEGF, FGF, TGF and collagenase (catalyses the breakdown of collagen) so do mast cells, platelets, T lymphocytes and endothelial cells
Third step of the wound healing process
3) Proliferative phase
Purpose – Surrounding healthy cells begin to proliferate. Formation of granulation tissue. Large production of collagen at injury site.
Last step of the wound healing process
4) Maturation phase (aka remodelling)
Scar contraction, collagen cross-linking, shrinkage and loss of oedema
