Lect 8 - Repair & Regeneration Flashcards
if cells cant regrow, what type of healing happens?
repair
is cells can regrow, what type of healing happens?
regeneration
if the damaging agent persists, what does this lead to
chronic infalmmation
what does tissue injury cause
acute inflammation
what is repair?
Damaged cells cannot be
replaced by like
Fibrosis and scarring
= healing by repair
what is regeneration?
Damaged cells replaced
by like
Tissue returns to normal
= healing by regeneration
in what type of healing do you lose specialist function of a tissue?
Fibrosis and scarring
= healing by repair
describe the nature of labile cell populations
High normal turnover
Active stem cell population
Excellent regenerative capacity
eg Epithelia
describe the nature of stable (quiescent) cell populations
Low physiological turnover
Turnover can massively increase if needed
Good regenerative capacity
eg liver, renal tubules
describe the nature of permanent cell populations
No physiological turnover
Long life cells
No regenerative capacity (nb recent stem cell research)
eg neurons, muscle cells
which types of cell populations engage in the cell cycle?
labile cells always in cycle. permanent cells never in cycle, Quiescent cells sometimes in cycle depending on conditions.
what Architectural considerations are there in healing?
Rebuilding of complex architectures limited - eg Glomeruli, lung
Survival of connective tissue framework essential eg cirrhosis
what causes loss of function in the cirrhotic liver?
There is collapse of the reticulin (connective tissue) framework of the liver so that regeneration of liver cells cannot repopulate the normal architecture. This leads to the formation of regenerative nodules divided by fibrous septa.
what injuries can destroy stem cells and therefore stop healing?
full thickness burns
radiation
(some others)
what controls regeneration?
Proliferation of stem cell / amplifying cell compartments
Covering of defect
Contact inhibition
Complex control by growth factors, cell-cell and cell-matrix interactions
what are the stages of maturation of granulation tissue?
Vascularity
Collagen, ECM - wound strength
Cellularity
What local factors inhibit healing?
Infection Haematoma Blood supply Foreign bodies Mechanical stress
what systemic factors inhibit healing?
Age Drugs (eg steroids) Anaemia Diabetes Malnutrition Catabolic states Vitamin C deficiency Trace metal deficiency
what factors increase the chances of healing by first intention?
Clean, uninfected surgical wound
Good haemostasis
Edges apposed eg with sutures or staples
what factors increase the chances of healing by second intention?
Extensive loss of tissue Apposition not physically possible Large haematoma Infection Foreign body
what are the similarities and differences of healing via first and second intention?
Not a fundamentally different process
2nd More florid granulation tissue reaction
2nd More extensive scarring
what happens when a fracture heals?
Haematoma is organised
Removal of necrotic fragments
Osteoblasts lay down woven bone (=callus)
Remodelling according to mechanical stress
Replacement by lamellar bone
note the new bone forms a lump around where the fracture was
what may cause non union of fractures?
Misalignment Movement Infection Interposed soft tissue Pre-existing bone pathology
how does the brain heal?
Neurons are terminally differentiated
Supporting tissue is glial cells rather than collagen and fibroblasts etc
Hence damaged tissue is removed, often leaving cyst
THERE IS GLIOSIS RATHER THAN SCARRING.
what is granulation tissue formation interestingly close to?
tumour formation. study of this may lead to new treatments.
