Regeneration and repair Flashcards
what processes are involved in wound healing?
- haemostasis (repair of blood vessels)
- acute inflammation
- regeneration and/or repair
what are the basic principles of regeneration?
- regrowth of cells
- only possible with minor injuries
- regeneration is a physiological process that constantly occurs
where do new cells come from?
- stem cells can differentiated into other types of cells
- stem cells also self renew
what are the 3 types of stem cells?
- totipotent - can form any cell
- multipotent - can form several different cells
- unipotent - only produce one cell
where are stem cells found?
- in epidermis: found in basal layer
- in intestinal mucosa: found at bottom of crypts
- in liver: found between hepatocytes
what are the different types of tissue in relation to their ability to repair and regenerate?
- labile tissue - constantly replicate cells e.g. endothelial of skin
- stable tissue - low level of replication but can undergo periods of high replication in response to damage e.g. smooth muscle
- permanent tissue - never normally replicates e.g. brain, skeletal muscle
what is the relationship between the different tissue types and the cell cycle?
- labile tissues - constantly cycle
- stable tissue - leave cell cycle (in G0) but can re-enter
- permanent tissue - leave cell cycle and cant re-enter
what does regeneration rely on?
regeneration relies on their being an intact tissue architecture
(if damage is substantial then the tissue must undergo repair)
what is repair/fibrosis?
replacement of funcitoning tissue with a scar
how do we know if regeneration or repair will occur?
Tissue type:
* if damage is to permanent tissue then it will always undergo repair/fibrosis
* if damage is to labile or stable tissue then there are 2 possible outcomes:
1. if collagen architecture is intact then regeneration occurs
2. if collagen framework or chronic inflammation occurs then repair occurs
what are the different stages of repair?
- haemostasis - seconds to minutes
- inflammation - digestion of blood clot - mins to days
- proliferation - capillaries, fibroblasts, myofibroblasts - forms granulation tissue - days to weeks
- remodelling - maturation of scar - reduced cell population + increased collagen - weeks to years
what is the function of granulation tissue formation in the proliferation stage of scar formation?
- fills gap
- capillaries supply oxygen and nutrients
- contracts to close wound
what are the different cells involved in fibrous repair?
- neutrophils and macrophages - phagocytosis, release of mediators and acute inflammation
- lymphocytes - eliminate pathogens + co-ordinate other cells
- endothelial cells - proliferation stage of repair
- fibroblasts - secrete collagen + elastin to form extracellular matrix
- myofibroblasts - has intracellular actin so can contract allowing for wound contraction
how do fibroblasts appear under the microscope?
spindle shaped nucleus + cytoplasmic extensions
what are myofibroblasts?
cell somewhere between a fibroblast and smooth muscle cell
appears very similar to a fibroblast under microscope