Wound healing Flashcards
(25 cards)
Regeneration
growth of cells and tissues to restore lost structure
requires intact tissue scaffold
The steps of repair of fibrosis involves granulation tissue
- digestion of debris by macrophages: starts within 24-48 hr
- proliferation of fibroblasts and ingrowth of new micro-vessels starting around 48 hrs. {Vessels are essential to provide nutrients for fibroblasts to synthesise collagen}
- Fibroblasts migrate into margins of wound
- Fibrosis (fibrous tissue production by fibroblasts - main component is collagen)
healing define
tissue response to a wound (skin), inflammatory processes in internal organs, cell necrosis in organs incapable of regeneration
superifical wound of epidermis
healing by regeneration only
deep wound with damage in the dermis
collagen scar
Four stages of healing
- Haemostasis
- inflammation
- proliferation
- granulation tissue (soft callus)
- scar - fibrosis (hard callus) - remodelling
- contraction
- scar maturation/ wound strength
labile cells
normally proliferate to replace cells that are continually being lost
e.g. gut epithelium
stable cells
do not normally proliferate but capable of doing so when needed e.g. fibroblasts
permanent cells:
rarely proliferate
e.g. CNS neurons
difference between first and second intention
first:
- margins can attach
- margins are sutured
- no infection
second
- margins not ready to attach
- infection
- margins are devitalised: bruised or necrotic
difference between first and second intention
first:
- margins can attach
- margins are sutured
- no infection
second
- margins not ready to attach
- infection
- margins are devitalised: bruised or necrotic
Healing by first intention
- Haemostasis: within seconds to minutes • Inflammation: within minutes to hours
- Scab formation
- Migration of fixed cells: within 24 hours • Regeneration: 3 days
- Early scarring: 7-10 days
- Scar maturation: 1 month-2 years
Healing by second intention
- haemostasis
- platelet plug
chemo-attraction:
- polymorphonuclear neutrophils
- monocytes
- lymphocytes
inflammation
- neutrophils (kill and secrete cytokines to cause inflammation)
- monocytes: (attracted to wound cytokines, extravasate and turn into macrophages and secrete more cytokines)
- lymphocytes (modulate extent of inflammation)
proliferation
Angiogenesis
fibroplasia
epitheliualisation
angiogenesis
necessary to support a wound env. that can repair the injury
Stimulated by:
- macrophage-derived growth factors
- hypoxia, fibronectin and hyaluronic acid
supplies oxygen and nutrients for fibroblast proliferation and production of wound matrix
fibroplasia
Fibroblasts migrate into wound on the fibrin scaffold left behind from haemostatic process
• Macrophage-derived growth factors stimulate proliferation of fibroblasts (collagen synthesised at an accelerated rate)
Epithelialisation
- cells in basal layer at wound edge flatten
- cells along margin divide to reform mature, mutlilayered epithelium
how can the epithelialisation be compromised
- bacteria
- protein exudate from leaky capillaries
- necrotic debris
- delayed epithelialisation: prolonged and profound inflammatory process
Remodelling
- modulation of proteins:
fibrin and collagen - Transformation of fibroblast cells: myofibroblasts
Collagen synthesis and degradation is controlled by what
metalloproteinases (produced by macrophages, epidermal cells, endothelial cells and fibroblasts)
Remodelling (!)
contracture of the wound:
- contraction of fibrin
- myofirboblasts
- fibroblasts and collagen lattice
Re-epithelialisation
Organisation
Summary
inflammatory phase
Fibrin&Plateletscab • Whitebloodcells
migrate from capillaries in response to cytokine signals
• Deadtissue&debris cleared
• Morecytokines released
summary
proliferative phase
Fibroblasts& endothelial cells enter wound site • Begin to proliferate • Endothelial cells suform new blood vessels • Fibroblasts lay down collagen fibres
