4 Regeneration and Repair Flashcards
What is a stem cell?
Cells with potentially limitless proliferation
What is regeneration?
The replacement of dead or damaged cells by functional, differentiated cells.
Define ‘unipotent’
Can only produce one type of differentiated cell
Define ‘multipotent’
Can produce several types of differentiated cell
Define ‘totipotent’
Can produce any type of cell
What is a ‘labile cell’?
The normal state is in active cell division resulting in rapid proliferation of cells
What is a stable cell?
Often in the resting state (G0) so the speed of regeneration is viable
What is a permanent cell?
A cell always in G0 so cannot divide or regenerate
How do growth factors help to control regeneration?
Promote expression of genes controlling the cell cycle
Express growth proteins and hormones
How does cell-cell contact control cell division?
Signalling adhesion molecules inhibit proliferation in cells which are touching. Loss of contact will promote proliferation until the cells touch again.
What is fibrous repair?
The replacement of functional tissue by scar tissue
When does fibrous repair occur?
After necrosis of permanent cells
After the collagen framework is destroyed
What are the key components of fibrous repair? (4)
Cell migration
Angiogenesis
Extracellular matrix production
Remodelling
What cell types are involved in fibrous repair?
Inflammatory cells- neutrophils, macrophages, lymphocytes
Endothelial cells
Fibroblasts
Why is angiogenesis important?
It provides access to the wound for inflammatory cells, fibroblasts, oxygen and other nutrients.
What induces angiogenesis?
Proangiogenic growth factors
Example: VEGF
What are the 5 stages of angiogenesis?
- ) Endothelial proteolysis
- ) Migration of endothelial cells
- ) Endothelial proliferation
- ) Endothelial maturation
- ) Recruitment of periendothelial cells
What is the function of extracellular matrix?
Supports and anchors cells
Sequesters growth factors
Allows cell migration
What is the mechanism of fibrous repair?
Inflammatory cells infiltrate a damaged area and a blood clot forms
The clot is replaced by granulation tissue
Angiogenesis occurs and extracellular matrix is produced
Myofibroblasts contract to reduce the wound volume
A fibrous scar is left behind
When does healing by primary intention occur?
An incised wounds with apposed edges
What happens in healing by primary intention?
The epidermis regenerates and the dermis undergoes fibrous repair. The granulation tissue then becomes scar tissue which matures.
When does healing by secondary intention occur?
At an infarct, ulcer, abscess or any large wound. The edges are unapposed and a large clot dries to form a scab.
How does skin heal by secondary intention?
The epidermis regenerates from the base up so lots of granulation tissue is produced. More contraction is needed to reduce the volume of the defect and a larger scar is produced.
How does a bone fracture heal?
Haematoma forms at the fracture site providing a framework for macrophages, fibroblasts and osteoblasts.
Capillaries develop
A callus forms and bone is laid down
Bone then remodels itself
Name 3 local factors affecting wound healing
Infection
Blood supply
Type, Size, Location
Foreign material
Name 3 general factors affecting wound healing
Age Drugs Dietary deficiencies General health Chronic illnesses
