Repair and Regeneration Flashcards
what’s the two different types of inflammation?
acute and chronic
what are the physiological changes to the cells after a repair?
scar formation
loss of function
cells cannot regrow
what are the physiological changes to the cell after a regeneration?
cells can regrow
restoration of the normal structure and function
what are the two most important factors in determining the outcome of injury?
the ability of the cells to replicate
the ability to rebuild complex architectural structures.
what are the stages of the cell cycle?
G1,
S,
G2,
M,
what are the characteristics of labile cell populations
High normal turnover
active stem cell population
excellent regenerative capacity
give an example of a labile cell population?
epithelia
what are the characteristics of stable cell populations?
low physiological turnover
turnover can massively increase if needed
good regenerative capacity
what is another name for stable cell populations
Quiescent
what is examples of quiescent cell populations?
liver, renal tubules
what are the characteristics of permanent cell populations?
No physiological turnover
long life cells
no regenerative capacity
give an example of a type of cells that have no regenerative capacity?
neurons
striated muscle cells
what type of replication do stem cells undergo?
asymmetric replication
where are stem cell pools present?
labile and stable cell populations
why is the survival of stem cells important and how can the survival be threatened?
CRUCIAL to regeneration
its vulnerable to radiation injury
what type of cell population are hepatocytes?
stable
how is regeneration of cells controlled?
contact inhibition
growth factors
cell-cell and cell-matrix interactions
explain the mechanism in which a minor skin abrasion that has is lost epidermis is regenerated?
cells at margins proliferate and spread out as a thin sheet across the dermis
once defect is covered, the stimulus for them to proliferate and mover is switched off via - contact inhibition.
Epidermis then grows from the base upwards
what is organisation 1?
this is the repair of specialised tissue by formation of fibrous scar.
what is produced in organisation 1?
granulation tissue produced on scaffold of fibrin
what is organisation 2?
this where the granulation tissue contracts and accumulates collagen, forming a scar
what is organisation a consequence of?
pneumonia a d infarction
what is the constituents of granulation tissue
capillary loops phagocytic cells - neutrophils -macrophages myofibroblasts
why is wound contraction important?
important for reducing volume of tissue for repair - reduce by 80%
what is healing by first intention?
this is a clean surgical wound which has been closed at the end of the procedure to maximise chance of healing
what are the stages for healing by first intention
- edges of the incision are joined by thin layer of fibrin. replaced by collagen covered by surface epidermis
- coagulated blood forms a scab
- epidermis grows over defect
why is a keratin filled cyst formed?
if the wound is still gaping after epidermis grows over defect, epidermal cells can grown down into defect. these usually stop growing but can remain and form the cyst.
what is a residual defect of healing by first intention?
inability to reconstruct the elastic network within the dermis
what is the difference between healing by second intention and first intention
fundamentally not a different process.
but the wound edges are not apposed.
more extensive scarring
what are some local factors that inhibit healing
infection haematoma blood supply foreign bodies mechanical stress
what are some systemic factors inhibit healing
age drugs i.e. steroids anaemia diabetes malnutrition catabolic states vitamin c deficiency trace metal deficiency
why does steroids inhibit healing?
it has immunosuppressive actions and therefore interfere with formation of granulation tissue
why does vitamin D deficiency inhibit healing?
vit. C is involved in collagen synthesis. collagen main protein in the ECM.
what is Keloid?
this is a dermal injury that sometimes followed by excessive fibroblast proliferation and collagen production. this is a genetically determined process
what are the steps of fracture healing?
- a haematoma is formed and organised.
- removal of necrotic fragments
- osteoblasts lay down disorganised woven bone
- remodelling according to mechanical stress
- replacement by more orderly lamellar bone
where are EGF from?
platelets
macrophages
saliva
plasma
what is the function of EGF?
mitogenic for keratinocytes and fibroblasts
stimulates granulation tissue formation
where are TGF-B
platelets T Lymphocytes macrophages endothelial cells keratinocytes smooth muscle cells fibroblasts
what is the function of the TGF-B?
chemotactic for PMNs, macrophages, lymphocytes, fibroblasts and smooth muscle cells
stimulate TIMP synthesis angiogenesis and fibroplasia
inhibits production MMPs and keratinocyte proliferation
where is PDGF from?
platelets, macrophages, endothelial cells, keratinocytes and smooth muscle cells
what is the function of the PDGF?
chemotactic for PMNs, macrophages, fibroblasts and smooth muscle cells
activates PMNs, macrophages and fibroblasts
mitogenic for fibroblasts, endothelial cells and smooth muscle cells
stimulates production of MMPs, fibronectin and HA stimulates angiogenesis
where is KGF from?
fibroblasts
what is the function of KGF?
Stimulates keratinocytes migration, proliferation and differentation
where is TNF from
macrophages, mast cells, T lymphocytes
what is the function of TNF?
activates macrophages, regulates other cytokines
where is the VEGF
many types of cells
what is the function of VEGF?
increases vascular permeability
mitogenic for endothelial cells
