Regeneration And Repair Flashcards
What are 3 different types of stem cells?
Unipotent only produce one type of differentiated cell eg epithelial
Multi potent can produce several types of differentiated cell eg haemopoietic
Totipotent can produce any type of cell eg embryonic stem cells
What is fibrous repair?
The replacement of functional tissue by scar tissue
What are the key components of fibrous repair?
Cell migration
Angiogenesis
Extracellular matrix
How is cell migration involved in fibrous repair?
Inflammatory cells migrate, neutrophils & macrophages phagocytise debris, lymphocytes & macrophages act as chemical mediators.
Endothelial cells migrate for angiogenesis
Fibroblasts migrate and secrete ECM proteins, myofibroblasts for wound contraction.
How does angiogenesis occur in fibrous repair?
Induced by proangiogenic growth factors eg VEGF.
Endothelial cells migrate by chemotaxis and proliferate. They mature and undergo tubular remodelling, recruit periendothelial cells.
What is the role of the extracellular matrix in fibrous repair?
It supports and anchors cells, separates tissue compartments, sequesters growth factors, allows communication between cells, facilitates cell migration.
How is fibrous repair controlled?
Inflammatory cells are recruited by chemotaxis.
Angiogenesis is due to angiogenesis cytokines in hypoxia and release of VEGF.
Fibrosis is due to macrophages releasing pro-fibrotic cytokines leading to fibroblast proliferation.
Outline the process of fibrous repair
- Infiltration of inflammatory cells: blood clot forms, neutrophils, macrophages & lymphocytes migrate into clot.
- Clot is replaces by granulation tissue. Capillaries & lymphatics form through angiogenesis. Fibroblasts migrate and differentiate, secrete ECM.
- Maturation. Cell population falls, collagen increases and matures & remodels. Myofibroblasts contract, decreases volume if defect. Vessels differentiate and are reduced, left with fibrous scar.
How is regeneration controlled?
Growth factors promote stem cell proliferation.
CONTACT INHIBITION: Contact between basement membrane and adjacent cells allows signalling through adhesion molecules to inhibit proliferation in intact tissue, loss of contact promotes proliferation.
When does healing by primary intention occur?
With an incised wound with opposed edges. Minimal blood clot and granulation tissue.
What happens in healing by primary intention?
Epidermis regenerates, dermis undergoes fibrous repair.
Sutures out at 5-10 days but maturation of scar tissue continues for up to 2 years.
Results in minimal contraction and scarring.
Risk of infection and abscess.
When does healing by secondary intention occur?
In larger wounds, with unopposed edges
How does healing by secondary intention occur?
The clot dries to form a scab, as the epidermis regenerates from the base up.
The repair process produces lots of granulation tissue, more contraction (to reduce the volume of the defect).
What local factors influence the efficacy of healing?
The type, size and location of the wound Lack of movement Blood supply Infection Foreign material Radiation damage
What general factors influence the efficacy of healing?
Age
Drugs (steroids)
General dietary deficiencies eg protein
Specific dietary deficiencies eg Vit C, essential amino acids
General state of health
Chronic diseases eg diabetes, rheumatoid arthritis
General cardiovascular status
What are some possible complications of repair and when are they likely to occur?
Insufficient fibrosis: leading to wound dehiscence, hernias, ulceration. Common in obesity, elderly people, malnutrition, steroids.
Excessive fibrosis: leading to cosmetic scarring, keloid scars, cirrhosis, lung fibrosis, hypertrophic scars.
Excessive contraction: leading to strictures and contractures
What is a stricture?
An obstruction of tubes/channels
What is a contracture?
A permanent shortening in muscle or joint tissue, limiting movement.
Define regeneration
The replacement of dead/damaged cells by functional differentiated cells derived from stem cells.
