Wound healing and repair Flashcards
1
Q
What does healing depend on?
A
- Retention of tissue scaffold
- Cells ability to regenerate
- Hypoxia, blood supply
2
Q
What is the role of macrophages in healing?
A
- secretion of cytokines and GFs
- Causes angiogenesis, multiplication of endothelial cells and division of stromal cells
- Recruits immune cells
3
Q
What is the role of endothelial cells in healing?
A
- ECs damaged → facilitation of platelet adherence to exposed ECM
- Platelets activated → more platelets
- Ecs→ trigger fibrin polymerisation - entraps RBCs
4
Q
What is the role of mast cells in wound healing?
A
Proteolytic enzyme release - can help in remodelling ECM
5
Q
What is the role of fibroblasts in wound healing?
A
- produce collagen and ECM proteins
- Cytokine and MMPs produced regulate composition of the extracellular environment
- Proliferate with tissue injury/hypoxia
- Transform to myofibroblasts
6
Q
What are the 4 stages of wound healing?
A
- Haemostasis
- Inflammation
- Proliferation
- Remodelling
7
Q
What occurs in haemostasis?
A
- Begins immediately
- Initial vasoconstriction
- Platelets adhere to the damaged endothelium which plugs the wound
- Fibrin mesh formed
- Blood vessels subsequently dilate which begins the inflammatory phase
8
Q
What occurs in the inflammatory phase?
A
- Removal of debris & bacteria
- Neutrophils reach their peak population at the site and decrease after 3 days
- Macrophages increase after debris removal
9
Q
What occurs in the proliferative phase of inflammation?
A
- Initiates filling & covering of the wound site
- The defect begins to be formed by immature connective tissue
- Granulation tissue forms over the defect
- On the body surface, re-epithelialisation occurs as epithelial cells migrate from the wound bed & margins to cover the surface
10
Q
What factors induce angiogenesis
A
- Hypoxia
- Cytokines
- Growth factors
- All induce VEGF which stimulates angiogenesis
11
Q
What are the stages of angiogenesis?
A
- Degradation of ECM
- Leads to migration of endothelial cells via chemostaxis
- Multiplication of endothelial cells
- Lumen formation
12
Q
What occurs in granulation formation?
A
- VEGF increases permeability → exudation of plasma proteins (fibrinogen)
- GFs (TGF-ß) and cytokines recruit and stimulate fibroblasts → deposits collagen
- Granulation tissue replaced by fibroblasts, collagen and other ECM components
13
Q
What stimulates and inhbuts MMPs?
A
- stimulated by some GFs and cytokines that stimuate collagen production, phagocytosis & physical stress
- inhbited by Steroids, TGF-Beta and tissue inhibitors (TIMPS)
14
Q
What occurs in the remodelling phase?
A
- Collagen fibres progressively reorganise, remodel & mature
- Wound bed progressively increases in tensile strength & flexibility
- Fibroblasts mature into myofibroblasts
- The wound margin contracts
15
Q
What are primary union of tissues?
A
When the wound edges are in close contact and can be closed by stitches or staples
