Wound healing Flashcards
what are the three tissue responses to injury?
-regeneration
-repair
-chronic inflammation
what is wound healing dependent on?
-capacity of tissue to regenerate
-type of wound and the degree of damage
what are the 6 types of wound?
-abrasion
-avulsion
-incision
-laceration
-puncture
-amputation
what are the three types of cells in terms of their renewal
-liable: constant cell renewal
-stable: slow renewal
-permenant: post mitotic
what are the two major components that undergo repair?
cells and the extracellular matrix
what does the extracellular matrix consist of?
-collagen
-basement membrane
-glycoproteins
-proteoglycans
-elastin
what are the steps of healing?
- haemostasis
2.inflammation - demolition
- proliferation
- maturation
what are the steps of haemostasis?
- reaction to injury
- truggeres platelet aggregation and activation of coagulation cascade
- haemostatic plug/ clot
what is the aims of inflammation?
-trigger phagocytosis
-to trigger plasma proteins and cause clotting factors, complement components and kininogens
-isolate, des
what are the steps leading up to inflammation?
- vasodilation and increased vascular permeability of the blood vessels
- plasma proteins of fibrinogen and fibronectin are released
- phagocytes are released
what are the symptoms of inflammation?
-rubor/ redness
-calor/ heat
-tumor/ swelling
-dolor/ pain
what cells are triggered in inflammation?
-neutrophils
-macrophages
-lymphocytes
-plasma proteins
what chemicals are triggered in haemostasis?
-platelets
-fibrin
-fibronectin
-transglutaminases
what cells are triggered in demolition
-mainly macrophages
-collagenases
what processes are triggered in proliferation?
-granulation
-anglogenisis
-extracellular matrix synthesis
-wound contraction
-epithelial proliferation
what processes are triggered in maturation?
-collagen cross linking
-remodelling
-capillary resorption
what are the steps of inflammation?
- vasodilation and vascular permeability
- plasma proteins of fibrinogen and fibronectin
- phagocytes are recruited
what does proliferation do?
replaces the wound by cells and scar tissue
what happens in the formation of granulation tissue?
-angiogenesis to form richly vascularised tissue
-deposition of non-collagenous ECM
-collagen synthesis
-scar tissue deposition
what are the growth factors in proliferation?
-EGF
-FGF
-PDGF
-TGFB
-NGF
what hormones are involved in proliferation?
insulin, glucagon and thyroid hormones
how long does cell regeneration in epithelial wound healing take?
3-7 days
what are the steps of granulation?
-endothelial cells spout
-new capillary bed is formed
-cell recruitment where inflammatory cells are triggered
-myofibroblasts released
-wound contraction occurs
-inward migration of myofibroblasts
what happens in wound maturation?
-maximum collagen accumulation that takes 2-3 months
-continuous remodelling so continual ECM syntehsis and degredation organisation
-organisation
-collagen cross linking causes increase in tensile strength
what causes a keloid scar?
excessive collagen deposition at wound site
what are the local wound healing factors?
-type, size and location
-vascular supply
-oxygen supply
-infection
-necrosis
-foreign material
-movement
what are the systemic wound healing factors?
-cardiovascular status
-nutritional status, vitamin A is essential for epithelial regeneration
-diseases such as diabetes or cancer
-drugs
Give 5 procedures where the eye would have to undergo wound healing
after:
-laser surgery such as PKP or LASIK
-cataract surgery
-glaucoma filtration surgery
-proliferative vitreoretinopathy
-laser photocoagulation
when would the cornea specifically have to undergo wound healing?
-infection
-trauma
-keratoplasty
-refractive surgery
What does the nature and extent of the wound healing response depend on?
chemical or mechanical cause.
-chemical triggers a superficial response
-mechanical triggers a penetrating response
What are the 5 refractive and transplant surgeries?
-photorefractive keratectomy (PRK)
-Laser-assisted in situ keratomileusis (LASIK)
-Laser-assisted sub-epithelial keratectomy (LASEK)
-Penetrating keratoplasty (PKP)
-Anterior lamellar keratoplasty (ALK)
what is PKP?
a full thickness transplant that replaces diseased cornea and is especially useful in cases of endothelial dysfunction
What is ALK?
a partial thickness graft of the epithelium and stroma and is for stromal pathologies without epithelial dysfunction
what is the process of epithelial wound healing? how long does the process take?
- rounding off of wound edge, epithelial differentiation disappears
- stem cells and TACs proliferate
- loss of cell attachments: hemidesmosomes
- migration as a sheet along a temporary matrix
- re-epithelial differentiation/ stratification
what is the process of stromal wound healing? What are the symptoms during the healing phase? how long is the healing phase?
- keratocyte apoptosis at wound site
- activation and proliferation of fibroblasts
- migration to wound site
- differentiation to myofibroblasts
- ECM remodelling as there is new synthesis of GAGs and collagen and degradation
symptoms:
-fibrosis and haze
-vision loss
takes 1-3 years
Give the steps to endothelial wound healing
1.cells migrate across Descemet’s membrane to compensate regions of loss
2. cells enlarge to fill in gaps in polymegathism and pleomorphism
when does endothelial healing need to occur?
if damaged human corneal endothelial cells are unable to regenerate
What are the regulators of corneal wound healing?
-tear fluid
-growth factors
-adhesion molecules
-proteolytic enzymes
what cell is responsible for wound contraction and why is wound contraction important?
myofibroblast, reduces wound size so faster healing
Which cells undergo cell division to generate cells for the process of epithelial regeneration in the cornea and skin?
-cornea: limbal epithelial stem cells; TACs on the basal corneal epithelium
-skin: epithelial stem cells in the basal layer; TACs in the basal layer
what are the steps of angiogenesis?
1.nearby capillary endothelial cell duplicates
2. this forms a tube of cells
3. this joins up with another tube of cells
4. this forms a new capillary bed at the wound site
what are the 3 categories that describe a cells proliferative potential?
-liable
-stabile
-permanent
