MoD - Wound Healing Flashcards
What does regeneration require?
The damage to the tissue to not be extensive and an intact CT scaffold.
What is regeneration?
The growth of cells and tissue to replace lost tissue structures
What is a labile tissue?
A continuously dividing tissue, one that proliferates through life e.g surface epithelia (GI, skin) and bone marrow
What is a stable tissue?
Normally has a low level of replication but can undergo rapid division in response to stimuli. E.e liver, kidney, WBC p, vascular cells (endothelial)
What is a permanent tissue?
Cells can’t undergo mitotic division e,g neurones, skeletal and cardiac muscle
What is a stem cell?
A precursor cell for many terminally differentiated cells.
When divided one daughter cell remains as a stem cell whilst the other differentiates to a mature non dividing cell.
Give an example of a pluripotent cell type?
Haemopoetic cells
When does fibrous repair occur?
If the collagen framework of a tissue is destroyed
If there is ongoing chronic inflammation
Or if there is necrosis of specialised parenchymal cells
Describe the process of fibrous repair?
Phagocytosis of necrotic tissue debris
Proliferation of endothelial cells (small capillaries grow)
Proliferation of fibroblasts and myofibroblasts
The granulation tissue becomes less vascular and matures into a fibrous scar
Scar matures and shrinks due to contraction of myofibroblasts
What is angiogenesis?
The formation of new blood vessels from the proliferation of endothelial cells
What is granulation tissue made of?
Fibroblasts (to synthesise collagen), myofibroblasts (wound contraction) endothelial cells (angiogenesis) immune cells (macrophages and neutrophils - for phagocytosis)
What do defects in collagen synthesis lead to?
Decreased healing ability
What is an autocrine control of fibrous repair?
Cell responds to its own signal
What is paracrine control of fibrous repair?
Cell signal acts on an adjacent cell
What are growth factors?
Polypeptides that act on specific cell surface receptors considered as ‘local hormones’ can stimulate proliferation or inhibition and cell locomotion.
What is epidermal growth factor?
This is produced by inflammatory cells, it is mitogenic for epithelial cells, hepatocytes and fibroblasts
It binds to epidermal growth factor receptors
What is vascular endothelial growth factor?
Induces BV development and growth of new vessels in tumours chronic inflammation and wound healing
What is platelet derived growth factor?
Stored in platelet a granules and released on activation. Also produced by smooth muscle macrophages and endothelial cells. Causes migration and proliferation of fibroblasts and monocytes.
What is tumour necrosis factor?
This induces fibroblast migration, proliferation and collagenase secretion (breaks down collagen)
What is contact inhibition?
This is when normal cells replicate until they have cells touching them. Cells adhere to each other by cadherins and adhere to the Extracellular matrix by integrins)
When does healing by primary intention occur?
This occurs in incision wounds, closed, clean with opposed edges.
There is only partial destruction of epithelia and CT cells.
What are the 6 simple stages of primary intention healing?
- Haemostasis (scab)
- Inflammation - neutrophils
- Macrophages appear- secrete cytokines - attracts cells
- Granulation tissue invades the space
- Fibroblasts produce collagen - scar
- Scar maturation
What are the differences in secondary intention healing?
This is seen in wounds with tissue loss and separated edges and in infection. Open wound is filled with granulation tissue. There is a larger clot and more necrotic debris
Inflammatory reaction is more intense
Wound contraction takes place - myofibroblasts
Substantial scar forms
Name some local factors affecting wound healing?
Size, location, type of wound Blood supply Denervation Local infection Foreign bodies Mechanical stress
Name some systemic factors affecting wound healing
Age Hypoxia Obesity Diabetes Malignancy Genetic disorders Drugs (steroids) Vitamin deficiency
What are some of the complications of fibrous repair?
Insufficient fibrosis - breakdown of wound
Excessive fibrosis - scarring, keloids
Disruption of complex tissue - cirrhosis
Excessive contraction - strictures
