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Wound Healing and Repair
Susan and Allison
Define the following cell types, give examples:
O Labile
O Stable
O Permanent
Continuously dividing- Epithelia e.g. Skin, GI, cervix,
urinary tract
Infrequent divisions but rapid if needed:- Liver, kidney, fibroblasts, smooth
muscle cells, endothelial cells, chondrocytes, osteocytes
Never divide in adult life- Cardiac muscle cells, nerve cells, skeletal muscle cells
What are the 3 main outcomes following tissue injury?
O RegenerationO Scarring
O What do we mean by each of the terms?
Restitution of the normal structure and function
Loss of function but structural stability restored
Difference between scar and fibrosis is exposure to stimuli (short term vs long term)
RegenerationO Definition: Restoration of normal
structure and functionO Can be restored as long as there is
minimal damage to tissue architecture and parenchyma cells can proliferate from residual stem cells
O 2 possible outcomes of regeneration...
RegenerationO 2 possible outcomes of regeneration:
1. ResolutionO Restoration of normal structure and functionO Need intact parenchyma or ability to produce
parenchymal cellsO Labile cells
2. Compensatory growthO Compensatory growth of cells to restore normal tissue
functionO Need intact architecture or ability to produce
parenchymal cellsO Stable cells
Fibrous repairO Definition: Healing by deposition of
connective tissue (scar)O Occurs when the parenchyma AND stroma
are damaged in labile or stable tissuesO Associated with loss of function of tissues
O What is the main problem with scar tissue?O It does not have the same tensile strength
that normal tissue has
What 3 main processes are involved fibrosis repair?
1. Inflammation O Macrophages clear out dead tissue
2. Granulation tissue O Angiogenesis,O Fibroblasts proliferate/migrate
3. Scar formation O Connective tissue remodelingO Recovery of tensile strength
Free chapter online : http://www.us.elsevierhealth.com/media/us/samplechapters/9781437707922/Chapter%2003.pdf
What are the 7 steps in cutaneous wound healing?
1. Formation of a blood clot2. Formation of granulation tissue3. Cell proliferation and collagen deposition4. Scar formation5. Wound contraction6. Connective tissue remodeling7. Recovery of tensile strength
What important factors are involved?
1. Formation of a blood clot (day 1)2. Formation of granulation tissue (day 3-5)
O Angiogenesis
3. Cell proliferation and collagen deposition (day 3-10)
4. Scar formation5. Wound contraction6. Connective tissue remodeling (day 15+)7. Recovery of tensile strength (3 months)
VEGF
TGF-β
PDGF and MMPs
What are the features of granulation tissue?
O Hallmarks:O AngiogenesisO Fibroblast proliferation
O Other features:O Inflammatory cellsO Oedema
Types of healing
O Primary intention:O Wound is artificially closed e.g.
stitches, graft
O Secondary intention:O Wound is not closed (spontaneous
healing)
Initial contractionEschar formsEpidermis regenerates at base
Granulation tissue bed
More contractionMore scarring
Takes longer than primary
What are the differences between primary and secondary intention healing? [6]
Loca
l Fa
ctors
• Infection prolongs inflammatory stage
• Mechanical factors
• Foreign bodies impairs fibrous repair
• Size of wound• Location of
wound• Type of wound
Syst
em
ic
Fact
ors• Metabolic Status
• Nutritional Status
• Hormones• Circulatory
status
What local factors influence wound repair? [6] What systemic
factors influence wound repair? [4]
What 3 main things can go wrong with repair?
1. Inadequate formation O Rupture O Ulceration
2. Excessive formationO Keloid – scar spreads outside the
boundary of the linesO Hypertrophic – excessive scar within
boundaries of woundO Proud flesh (granulation tissue)
3. Formation of contractureO Secondary intention healing may result in
excessive contracture