Lect 8 - Repair & Regeneration

Question 1

if cells cant regrow, what type of healing happens?

Answer 1

repair

Question 2

is cells can regrow, what type of healing happens?

Answer 2

regeneration

Question 3

if the damaging agent persists, what does this lead to

Answer 3

chronic infalmmation

Question 4

what does tissue injury cause

Answer 4

acute inflammation

Question 5

what is repair?

Answer 5

Damaged cells cannot be
replaced by like
Fibrosis and scarring
= healing by repair

Question 6

what is regeneration?

Answer 6

Damaged cells replaced
by like
Tissue returns to normal
= healing by regeneration

Question 7

in what type of healing do you lose specialist function of a tissue?

Answer 7

Fibrosis and scarring

= healing by repair

Question 8

describe the nature of labile cell populations

Answer 8

High normal turnover
Active stem cell population
Excellent regenerative capacity
eg Epithelia

Question 9

describe the nature of stable (quiescent) cell populations

Answer 9

Low physiological turnover
Turnover can massively increase if needed
Good regenerative capacity
eg liver, renal tubules

Question 10

describe the nature of permanent cell populations

Answer 10

No physiological turnover
Long life cells
No regenerative capacity (nb recent stem cell research)
eg neurons, muscle cells

Question 11

which types of cell populations engage in the cell cycle?

Answer 11

labile cells always in cycle. permanent cells never in cycle, Quiescent cells sometimes in cycle depending on conditions.

Question 12

what Architectural considerations are there in healing?

Answer 12

Rebuilding of complex architectures limited - eg Glomeruli, lung

Survival of connective tissue framework essential eg cirrhosis

Question 13

what causes loss of function in the cirrhotic liver?

Answer 13

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.

Question 14

what injuries can destroy stem cells and therefore stop healing?

Answer 14

full thickness burns
radiation
(some others)

Question 15

what controls regeneration?

Answer 15

Proliferation of stem cell / amplifying cell compartments

Covering of defect

Contact inhibition

Complex control by growth factors, cell-cell and cell-matrix interactions

Question 16

what are the stages of maturation of granulation tissue?

Answer 16

Vascularity

Collagen, ECM - wound strength

Cellularity

Question 17

What local factors inhibit healing?

Answer 17

Infection
Haematoma
Blood supply
Foreign bodies
Mechanical stress

Question 18

what systemic factors inhibit healing?

Answer 18

Age
Drugs (eg steroids)
Anaemia
Diabetes
Malnutrition
Catabolic states
Vitamin C deficiency
Trace metal deficiency

Question 19

what factors increase the chances of healing by first intention?

Answer 19

Clean, uninfected surgical wound
Good haemostasis
Edges apposed eg with sutures or staples

Question 20

what factors increase the chances of healing by second intention?

Answer 20

Extensive loss of tissue
Apposition not physically possible
Large haematoma
Infection
Foreign body

Question 21

what are the similarities and differences of healing via first and second intention?

Answer 21

Not a fundamentally different process
2nd More florid granulation tissue reaction
2nd More extensive scarring

Question 22

what happens when a fracture heals?

Answer 22

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

Question 23

what may cause non union of fractures?

Answer 23

Misalignment
Movement
Infection
Interposed soft tissue
Pre-existing bone pathology

Question 24

how does the brain heal?

Answer 24

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.

Question 25

what is granulation tissue formation interestingly close to?

Answer 25

tumour formation. study of this may lead to new treatments.