healing and repair

Question 1

what three cell types does healing depend on

Answer 1

-labile cells
-stable cells
-permanent cells

Question 2

what are labile cells

Answer 2

constantly in a state of replication
active stem cells continually in cell cycle
skin epithelial cells
intestinal epithelial cells
bone marrow cells

Question 3

give three examples of labile cells

Answer 3

skin epithelial cells
bone marrow cells
intestinal epithelial cells

Question 4

what are stable cells

Answer 4

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

Question 5

give three examples of stable cells

Answer 5

fibroblasts
epithelial cells of kidney and liver
smooth muscle

Question 6

what are permanent cells

Answer 6

incapable of mitosis or organised replication
no functional stem cell population
neurones
skeletal myocytes
cardiac myocytes

Question 7

what are the two processes of healing

Answer 7

regeneration and repair

Question 8

what cells are involved in regeneration

Answer 8

labile and stable cells

Question 9

explain how regeneration works

Answer 9

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

Question 10

explain how repair works

Answer 10

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

Question 11

permanent cell populations

Answer 11

pure repair
no regeneration of original tissue
heart-scar formation
brain-reactive gliosis

Question 12

list the four stages of wound healing

Answer 12

-haemostasis
-inflammatory
-proliferative
-remodelling

Question 13

explain how the first stage of wound healing of the skin occurs

Answer 13

damaged vessels constrict
platelets stick together to seal the leak
coagulation to reinforce the platelet plug with thrombus

Question 14

how does the inflammatory phase of wound healing occur

Answer 14

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

Question 15

how are fibroblasts involved in wound healing

Answer 15

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

Question 16

how does the proliferative phase of wound healing occur

Answer 16

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

Question 17

how does the remodelling phase work

Answer 17

collagen fibres are realigned along tension lines
replacement of type iii collagen by type i
cross linking of collagen fibres
closure of wound

Question 18

what three things may control healing

Answer 18

-growth factors
-hormones
-cell to cell and cell and matrix interactions

Question 19

how can growth factors control healing

Answer 19

epidermal growth factor, vascular endothelial growth factor, fibroblast growth factor, platelet derived growth factor

Question 20

how can hormones control healing

Answer 20

growth hormone,
acth
oestrogen

Question 21

how can cell to cell and cell to matrix interactions control healing

Answer 21

density dependent regulation of cell growth
cadherin, integrin signalling

Question 22

what are the four types of healing

Answer 22

primary intention
secondary intention
delayed primary closure
healing of bone fracture