healing and repair Flashcards
what three cell types does healing depend on
-labile cells
-stable cells
-permanent cells
what are labile cells
constantly in a state of replication
active stem cells continually in cell cycle
skin epithelial cells
intestinal epithelial cells
bone marrow cells
give three examples of labile cells
skin epithelial cells
bone marrow cells
intestinal epithelial cells
what are stable cells
low level of replication under normal circumstances
stem cells mostly in G0 phase
ability of rapid replication with the correct stimulus
epithelial cells of kidney and liver
fibroblasts
smooth muscle
give three examples of stable cells
fibroblasts
epithelial cells of kidney and liver
smooth muscle
what are permanent cells
incapable of mitosis or organised replication
no functional stem cell population
neurones
skeletal myocytes
cardiac myocytes
what are the two processes of healing
regeneration and repair
what cells are involved in regeneration
labile and stable cells
explain how regeneration works
labile and stable cells
needs a supporting framework
residual framework (pure regeneration)
granulation tissue. fibroblast framework as part of repair
from viable stem cells at edge of wound
explain how repair works
replacement of injured cells, fibrosis, necrosis in permanent cells
damaged area of tissue becomes a scar
occurs when supporting framework of labile or stable tissue cells is destroyed
permanent cell populations
pure repair
no regeneration of original tissue
heart-scar formation
brain-reactive gliosis
list the four stages of wound healing
-haemostasis
-inflammatory
-proliferative
-remodelling
explain how the first stage of wound healing of the skin occurs
damaged vessels constrict
platelets stick together to seal the leak
coagulation to reinforce the platelet plug with thrombus
how does the inflammatory phase of wound healing occur
injured blood vessels leak transudate
damaged cells pathogens and bacteria are removed
neutrophils clear invading microbes by phagocytosis, produce proteases and oxygen reactive species
lymphocytes exact role is unclear but could be involved in fibroblast activity
cd8 t cells cytotoxic t cells involved in down regulating and healing response as the wound closes
t cell depletion results in weaker wound
macrophages are involved throughout the healing process
early- release cytokines for recruitment
resolution- clear cell debris
regeneration- stimulates keratinocytes, fibroblasts and angiogenesis. transition into proliferative phase of healing
how are fibroblasts involved in wound healing
FGF1 FGF2 are potent angiogenic factors
produce granulation tissues
main signals are PDGF and EGF
collagen type iii reticular fibres
glycosaminoglycans
fibronectin
elastin fibres
type iii to type 1 collagen
tissue fibroblasts become myofibroblasts
how does the proliferative phase of wound healing occur
rebuilding of wound with collagen and extracellular matrix
fibroblast migration and angiogenesis (VEGF, FGF)-granulation tissue
release of growth factors PDGF TGF beta and re-epithelialisation of wound
differentitaion of fibroblasts to myofibroblasts
how does the remodelling phase work
collagen fibres are realigned along tension lines
replacement of type iii collagen by type i
cross linking of collagen fibres
closure of wound
what three things may control healing
-growth factors
-hormones
-cell to cell and cell and matrix interactions
how can growth factors control healing
epidermal growth factor, vascular endothelial growth factor, fibroblast growth factor, platelet derived growth factor
how can hormones control healing
growth hormone,
acth
oestrogen
how can cell to cell and cell to matrix interactions control healing
density dependent regulation of cell growth
cadherin, integrin signalling
what are the four types of healing
primary intention
secondary intention
delayed primary closure
healing of bone fracture
