8. Repair and Regeneration

Question 1

Regenration occurs when?

Answer 1

After acute inflammation, if the cells can regrow

Question 2

Repair occurs when?

Answer 2

After acute inflammation, if the cells cannot regrow

Question 3

After regeneration, are the tissues normal or scarred?

Answer 3

Damaged cells replaced by like

Tissue returns to normal

Question 4

After repair, are the tissues normal or scarred?

Answer 4

Damaged cells cannot be replaced by like

Fibrosis and scarring

Question 5

After regeneration, do the tissues still have specialised function?

Answer 5

Yes, tissue restores specialised function

Question 6

After repair, do the tissues still have specialised function?

Answer 6

No, loss of specialised function

Question 7

Name 3 types of kinetic cell populations

Answer 7

• liable
• stable
• permanent

Question 8

What are the main characteristics of labile cell populations?

Answer 8

• high normal turnover
• active stem cell population
• excellent regenerative capacity

Question 9

Give an example of a labile cell population

Answer 9

Epithelia

Question 10

What does ‘high turnover rate’ mean in terms of tissues?

Answer 10

Constantly producing and shredding off old cells. Do this to maintain integrity

Question 11

In which zone of the tissue do active stem cells sit?

Answer 11

In the basal zone

Question 12

What does ‘regenerative capacity’ mean?

Answer 12

Capacity to heal by regeneration

Question 13

What are the main characteristics of stable (quiescent) cell populations?

Answer 13

• low physiological turnover
• turnover can massively increase if needed
• good regenerative capacity

Question 14

Give examples of stable (quiescent) cell populations

Answer 14

• liver

- renal tubules

Question 15

What are the main characteristics of permanent cell populations?

Answer 15

• no physiological turnover
• long life cells
• no regenerative capacity

Question 16

Give examples of permanent cell populations

Answer 16

• neurons

- muscle cells

Question 17

Cell types which are very specialised eg. neurones tend to be which type of cell population? (kinetics)

Answer 17

Permanent cell populations

Question 18

Which cell populations are at the end of the differentiation capacity and have lost the ability to divide?

Answer 18

Permanent cell populations

Question 19

Which type of cell population is good at switching on turnover when the need arises?

Answer 19

Stable (quiescent)

Question 20

Which type of cell population constantly goes round the cell cycle?

Answer 20

Labile

Question 21

Stable cell populations can come and go out of the cell cycle. At which stage do the go back in?

Answer 21

G1

Question 22

Why does a cirrhotic liver consist of regenerative nodules divided by fibrous septa?

Answer 22

There is a collapse of the reticulin (connective tissue) framework of the liver so that the regeneration of liver cells cannot repopulate the normal architecture

Question 23

What noxious agents may cause long term persistent long term damage to the liver (cirrhosis)?

Answer 23

• alcohol
• some hepatitis viruses
• autoimmune damage

Question 24

What are the stages from stem cells to terminal differentiation?

Answer 24

• stem cell compartment
• amplifying cell compartment
• differentiating compartment
• terminal differentiation

Question 25

Name some features of stem cells

Answer 25

- prolonged self-renewal - asymmetric replication - reservoirs present in many adult tissues - when a stem cell divides, it produces another stem cell as well as a cell that goes up in the diagram

Question 26

What is crucial for regeneration to be able to take place?

Answer 26

Survival of stem cells

Question 27

What can damage stem cells?

Answer 27

- full thickness burn | - radiation

Question 28

What controls regeneration?

Answer 28

- proliferation of stem cell/amplifying cell compartments - covering of defect - contact inhibition - complex control by growth factors, cell-cell and cell-matrix interactions

Question 29

Why might a cell population be incapable of cell renewal?

Answer 29

- may be a permanent cell population | - may be loss of stem cells

Question 30

What may a white area on heart muscle tissue be?

Answer 30

Fibrous scar tissue (as heart cells are a permanent cell population) - a result of healing of a myocardial infarct by repair

Question 31

What are the 3 main components of granulation tissue?

Answer 31

- new capillary loops (due to proliferation of endothelial cells from surrounding vessels) - phagocytic cells (neutrophils, macrophages) from acute inflammatory reaction, role is to remove dead tissue - myofibroblasts (lay down matrix components, collagen etc.) normal components of fibrous connective tissue

Question 32

What is the process of new blood vessels forming in granulation tissue?

Answer 32

- endothelial cell proliferation - buds - canalisation - new vessels

Question 33

How does a wound contract?

Answer 33

Fibroblasts acquire myofibrils and become myofibroblasts and therefore gain contractile ability - this allows wound contraction = reduces area

Question 34

Myofibroblasts causes wounds to contract. What problems may arise from this?

Answer 34

- contractures after burns | - oesophageal peptic strictures (narrowing)

Question 35

What happens as granulation tissue matures?

Answer 35

- vascularity decreases - cellularity decreases - collagen and ECM wound strength increases

Question 36

Maturation of the granulation tissue is necessary in complete repair. About how long does this normally take?

Answer 36

3 months

Question 37

Which drug generates catabolic state and impairs healing?

Answer 37

Steroids such as prednisolone Breaks down proteins and therefore interferes with the healing process

Question 38

How does malnourishment impair healing?

Answer 38

Lack of proteins which are required for healing by repair

Question 39

How does anaemia impair healing?

Answer 39

Affects oxygen supply

Question 40

What are two types of healing?

Answer 40

- healing by first (primary) intention | - healing by second (secondary) intention

Question 41

In what circumstances would healing by first/primary intention occur?

Answer 41

- clean, uninfected surgical wound - good homeostasis - edges apposed eg. with sutures or staples

Question 42

What would the end result of healing by first intention be?

Answer 42

A neat scar

Question 43

Under what circumstances would healing by second intention occur?

Answer 43

- wound edges not apposed - extensive loss of tissue - apposition not physically possible - large haematoma - infection - foreign body

Question 44

What is different in healing by secondary intention compared to healing by first intention?

Answer 44

- more florid granulation tissue reaction | - more extensive scarring

Question 45

How strong is a wound when sutures are taken out?

Answer 45

10% wound strength | day 7

Question 46

What are the general stages in fracture healing?

Answer 46

- normal bone fractures - haematoma at fracture site - callus at fracture site - lamellar bone replaces woven - remodelled to make normal bone

Question 47

What do osteoblasts do?

Answer 47

Lay down woven bone (=callus)

Question 48

What is a callus?

Answer 48

The bony healing tissue which forms around the ends of broken bone

Question 49

A fractured bone remodels according to what?

Answer 49

Mechanical stress

Question 50

The callus formed in a fracture is replaced by what?

Answer 50

Lamellar bone

Question 51

What causes non-union of fractures?

Answer 51

- misalignment - movement - infection - interposed soft tissue - pre-existing bone pathology = pathological fracture

Question 52

A pathological fracture is when there is non-union of fractures due to pre-existing bone pathology. Give an example of this

Answer 52

Tumour metastasis causing weakening of bone

Question 53

To what degree are neurones differentiated?

Answer 53

Neurons are terminally differentiated

Question 54

What is the supporting tissue int the brain?

Answer 54

Glial cells | rather than collagen and fibroblasts etc

Question 55

What are glial cells

Answer 55

They are cells that provide support and protection for neurons (the supporting tissue in the brain)

Question 56

How does healing occur in the brain?

Answer 56

Damaged tissue is removed, leaving a cyst The cyst will be surrounded by reactive gliosis (gliosis rather than scarring)

Question 57

What is gliosis?

Answer 57

Alternative to scarring, happens during healing in the brain It is a change in glial cells in response to damage to the CNS Involved the proliferation of glial cells (astrocytes etc)

Question 58

In general, how is healing controlled?

Answer 58

Tightly controlled by complex networks of cytokines etc.