Regeneration & Repair Flashcards
Define unipotent, totipotent and multipotent respectively
Only produces one type of differentiated cell
Can produce any type of cell
Produces several types of differentiated cells
Define regeneration
Replacement of dead or damaged cells by functional, differentiated cells.
What are labile cells?
‘Normal’ cells - the normal state is active cell division. Usually proliferate rapidly.
What are stable cells?
Normal state is the resting state. Speed of regeneration is variable.
What are permanent cells?
They cannot divide and cannot regenerate.
How do growth factors control regulation?
They promote proliferation in stem cell populations. Extracellular signals are transduced into cells. Promote expression of genes controlling the cell cycle. Hormones e.g. oestrogen.
What are the key components of fibrous repair?
Cell migration, angiogenesis and extracellular matrix production and remodelling.
What is angiogenesis and why is it needed?
Development of a blood supply and it’s vital for healing because it provides access to the wound.
What cell types are involved in fibrous repair?
Inflammatory cells, endothelial cells and fibroblasts/myofibroblasts
Describe the process of angiogenesis
Endothelial proteolysis of basement membrane, migration of endothelial cells via chemotaxis, endothelial proliferation, endothelial maturation and tubular remodelling, recruitment of periendothelial cells
What is the function of the extracellular matrix?
Supports and anchors cells Separates tissue compartments Sequesters growth factors Communication Facilitates cell migration
Describe the synthesis of fibrillar collagen
Polypeptide alpha chains synthesised in ER, enzymatic modification (vitamin C hydroxylation), alpha chains align and cross - procollagen triple helix, soluble procollagen secreted, cleavage, tropocollagen polymerises (fibrils), slow remodelling
What does the matrix group do?
Organise and orientate cells and support cell migration
What do proteoglycans do?
Matrix organisation, cell support, regulate availability of growth factors
What does elastin do?
Provide elasticity
What are the three main stages in fibrous repair?
Inflammatory cell infiltrate, clot replaced by granulation tissue and maturation
What happens during the inflammatory cell infiltrate stage of fibrous repair?
Blood clots, acute inflammation peripherally, chronic inflammation.
What happens when clots are replaced by granulation tissue?
Clot replaced by granulation tissue, angiogenesis (capillaries & lymphatics infiltrate), extracellular matrix is produced, vessels sprout, vascular network is formed. Collagen synthesis.
What happens during maturation in fibrous repair?
Cell population falls, collagen production increases. Myofibroblasts contract and decrease the volume of the defect. Vessels differentiate and are reduced. Fibrous scar is formed.
How is fibrous repair controlled?
Inflammatory cells recruited by chemotaxic gradients
Angiogenesis - platelets, ECM and others produce angiogenic cytokines in response to hypoxia
Fibrosis - macrophages etc
When does healing by primary intention occur?
Incised wound, apposed edges. There is minimal clot and granulation tissue. Regeneration of epidermis. Dermis undergoes fibrous repair.
When does healing by secondary intention occur?
Infarct, ulceration or large wounds. Unapposed wound edges, large clot dries (ESCHAR formation). Epidermis regenerates from base up. Produces more granulation tissue.
What factors influence wound healing?
Local factors and general factors
Give some examples of local factors affecting wound healing?
Apposition, lack of movement, blood supply, infection, foreign material, radiation damage
Give some examples of general factors
Drugs, hormones, dietary deficiencies, general health (CVS status)
What are possible complications of chronic inflammation?
Insufficient fibrosis leading to wound dehiscence, herniation, ulceration.
Excessive fibrosis - cosmetic scarring, keloids, cirrhosis and lung fibrosis
Excessive contraction - obstruction of tubes (strictures), limited movement
What is a pressure sore?
Who is it most common in?
A pressure sore is an area that has continual pressure applied to it, usually due to immobilisation. Patients who lie in bed for extended periods of time can put pressure on their backs and so can get pressure sores. Older patients and immobilised patients are most at risk.
How fast do nerves grow?
1 mm a day
What is the name of the process that affects anything distal to the damaged nerve?
Walarian degeneration - anything distal to severed nerve dies off - macrophages infiltrate and thus you lose the myelin sheath. Outer tube of myelin nerve stays there
