PP: Regeneration And Repair Flashcards
Define the term regeneration.
Restitution with no, or minimal, evidence that there was a previous injury.
Define the term resolution.
Resolution refers to the complete restoration of the tissue structure and function.
What is meant by labile tissues?
Short lived cells that are replaced from cells derived from stem cells.
Give some examples of labile tissues.
- Surface epithilia
- Haematopoietic tissues
What is meant by stable tissues?
Cells with normally low levels of replication but if necessary they can undergo rapid proliferation.
Both stem cells and mature cells proliferate.
Give some examples of stable tissues.
- Liver parenchyma
- Bone
- Endothelium
What is meant by permanent tissues?
Mature cells cannot undergo mitosis and no or only few stem cells are present.
Give some examples of permanent tissues.
- Neural tissue
- Skeletal muscle
- Cardiac muscle
What is the role of stem cells?
To replace lost or damaged cells in tissues.
What is asymmetric replication?
When stem cells divide, one cell remains as a stem cell, the other becomes a mature cell.
Define unipotent stem cell.
Cells which can only produce one type of differentiated cell e.g. Epithelia
Define multipotent stem cell
Has the ability to produce several types of differentiated cells e.g. Heamatopoietic stem cells
Define totipotent stem cells.
Embryonic stem cells which have the ability to produce any type of cell and therefore any tissues of the body.
In what circumstance can regeneration occur?
- If the damage occurs in labile or stable tissue
- If the tissue damage is not extensive
What is fibrous repair?
Healing with formation of fibrous connective tissue (scar)
When does fibrous repair occur?
- Significant tissue damage
- permanent/ complex tissue is damaged
Describe the cascade of fibrous repair.
- Blood clots
- Neutrophils infiltrate and digest the clot
- Macrophages and lymphocytes are recruited
- Vessels sprout and myofibrils recruited
- Collagen synthesised and matures
- Remodelling occurs
What cells are involved in fibrous repair?
- Inflammatory cells
- Endothelial cells
- Fibroblasts
- Myofibroblasts
What is the role of inflammatory cells in fibrous repair?
- Phagocytosis of debris by neutrophils and macrophages
- Production of chemical mediators by lymphocytes and macrophages
What is the role of endothelial cells in fibrous repair?
Proliferation resulting in angiogenesis (growing of blood vessels)
What is the role of fibroblasts in fibrous repair?
Produce extracellular matrix proteins e.g. Collagen
What is the role of myofibroblasts in fibrous repair?
Responsible for wound contraction
What are the components of granulation tissue?
- Developing capillaries
- Fibroblasts and myofibroblasts
- Chronic inflammatory cells
What is the function of granulation tissue?
- Fills the gap
- Capillaries supply oxygen, nutrients and cells
- Contracts and closes the hole
Name some diseases that are as a result of defective collagen synthesis.
- Scurvy
- Euler-Danlos syndrome
- Osteogenesis imperfecta
- Alport syndrome
What is scurvy?
A vitamin C deficiency which results in shit hydroxylation of procollagen alpha chains leading to reduced cross-linking and defective helix formation.
What is Euler-Danlos syndrome?
A heterogenous group of 11 inherited disorders which results in defective conversion of procollagen to tropocollagen.
It presents with poor wound healing and hyper-extensible skin.
What is osteogenesis imperfecta?
Extreme skeletal fragility due to lack of type 1 collagen.
What is Alport syndrome?
Usually X-linked disease which makes IV collagen abnormal (which affects the basement membrane)
How are regeneration and repair controlled?
Cell signalling via:
- Hormones
- Local mediators
- Direct cell-cell or cell-stroma contact
Explain the importance of concept of contact inhibition.
Cadherins bind cells to one another and integrins bind cells to to the extracellular matrix.
This inhibits proliferation in intact tissue and promotes proliferation in damaged tissues.
What is healing by primary intention?
The healing that takes place in non infected wounds where the number of death of epithelial and connective tissue cells is only small.
What occurs during primary healing?
- Epidermis regenerates
- Dermis undergoes fibrous repair
- Minimal contraction and scarring
- Good strength
What is healing by secondary intention?
- Considerable wound contraction
- Substantial scar formation which results in a new epidermis often thinner than usual
- Takes longer than healing by primary intention
What occurs during secondary intention?
- Initially occurs as a scan which contracts as it drys and shrinks
- After 1 week, myofibroblasts appear and contract (drawn into the centre)
Name some things that can influence wound healing.
- Type, size, location of wound
- Mechanical stress
- Blood supply
- Local infection
- Foreign bodies (likely to get an infection)
What general things can influence wound healing?
- Age
- Anaemia
- Obesity
- Diabetes
- Genetic disorders
- Drugs
- Vit deficiency
- Malnutrition
Name 3 complications of fibrosis and explain them.
- Insufficient fibrosis (e.g. In obesity there is wound dehiscence)
- Formation of adhesions (These can compromise organs or block tissues)
- Loss of function (due to replacement of specialised cells by scar tissue)
