7. Repair and Regeneration

Question 1

what is a scar?

Answer 1

an area of fibrous tissue, a manifestation of healing by repair

Question 2

what is a stem cell niche?

Answer 2

a microenvironment within the specific anatomical location of stem cells, which interacts with stem cells o regulate cell fate

Question 3

what does the mechanism of healing depend upon?

Answer 3

whether or not cells can regrow

Question 4

how do cells heal if they can be replaced?

Answer 4

regeneration and restitution of specialised function

Question 5

how do cells heal if they cannot be replaced?

Answer 5

fibrosis and scarring - loss of specialised function

Question 6

what are the different types of cell populations

Answer 6

labile
stable/quiescent
permanent

Question 7

what are the characteristics of a labile population?

Answer 7

high normal turnover
active stem cell population
excellent regenerative capacity
eg. epithelia

Question 8

what are the characteristics of a stable population?

Answer 8

low physiological turnover but can be massively increased if needed
good regenerative capacity
eg. liver, renal tubules

Question 9

what are the characteristics of a permanent population?

Answer 9

no physiological turnover
long life cells
no regenerative capacity
very specialised structure and function
eg. neurons, muscle cells

Question 10

what does regeneration depend on?

Answer 10

the structure that needs to be built, since it is not only the epithelium that gets damaged. epithelium cannot regenerate the rest of the functional tissue

Question 11

what are the characteristics of stem cells?

Answer 11

prolonged self renewal
asymmetric replication
reservoirs present in many adult tissues
survival is crucial to regenration

Question 12

what are the mechanisms in place for the control of regeneration?

Answer 12

1. proliferation of stem cell components
2. covering of defect
3. contact inhibition
4. complicit control by growth factors, cell-cell and cell-matrix interactions

Question 13

what is repair?

Answer 13

when the normal structure is not replaced, healing bu non-specialised fibrous tissue

Question 14

what does the granulation tissue contain?

Answer 14

new capillary loops
phagocytic cells
myofibroblasts which synthesise collagen and ECM. acquire myofibrils and contractile ability, leading to wound contraction

Question 15

what happens as the granulation tissue matures?

Answer 15

vascularity and cellularity decrease, collagen, ECM and wound strength increase

Question 16

what local factors inhibit healing?

Answer 16

infection
haematoma
blood supply
foreign bodies
mechanical stress

Question 17

what is a haematoma?

Answer 17

a solid swelling of clotted blood within tissues

Question 18

what systemic factors inhibit healing?

Answer 18

age
drugs
anaemia
diabetes
malnutrition
catabolic states 
Vit. C deficiency
trace metal deficiency

Question 19

what is the criteria for healing by first intention?

Answer 19

wound edges need to be apposed to one another
good haemostats
clean and uninfected wound

Question 20

what is the process of healing by first intention?

Answer 20

1. formation of initial fibrinous clot, which heals by a process of organisation
2. formation of a fibrous scar by granulation occurring and maturing
3. fibrous union, contraction. scar aimed to be as small and neat as possible

Question 21

when doe wounds heal by second intention?

Answer 21

when wound edges are not apposed due to:

1. extensive loss of tissue
2. apposition not physically possible
3. large haematoma
4. infection
5. foreign body oresent

Question 22

what is the consequence of healing by second intention?

Answer 22

more floris granulation tissue reaction and more extensive scarring
fundamentally similar reaction

Question 23

when does non-union of fractures occur?

Answer 23

1. misalignment
2. movement
3. infection
4. interposed soft tissue
5. pre-existing bone pathology

Question 24

how do wounds in the brain heal?

Answer 24

supporting tissue in the brain is glial cells rather than collagen and fibroblasts, therefore damaged tissue is removed, leaving a cyst, and healing takes place by gliosis rather than scarring

Question 25

how is healing controlled?

Answer 25

complex networks of cytokines

Question 26

what is the function of epidermal growth factor (EGF)?

Answer 26

stimulates granulation tissue formation

Question 27

what is the function of transforming growth factor beta (TGF-B)?

Answer 27

stimulates TIMP synthesis, angiogenesis and fibroplasia, inhibits production of MMPs and keratinocyte proliferation

Question 28

what is the function of platelet derived growth factor (PDGF)?

Answer 28

activates PMNs, macrophages and fibroblasts. mitogenic for fibroblasts, endothelial cells and smooth muscle cells. stimulates angiogenesis

Question 29

what is the function of keratin growth factor (KGF)?

Answer 29

stimulates keratinocyte migration, proliferation and differentiation

Question 30

what is the function of tumour necrosis factor (TNF)?

Answer 30

activates macrophages, regulates other cytokines

Question 31

what is the function of vascular endothelial cell growth factor (VEGF)?

Answer 31

increases vascular permeability, mitogenic for endothelial cells

Question 32

what is the function of transforming growth factor alpha (TGF-A)?

Answer 32

similar to EGF, stimulates replication of hepatocytes and most epithelial cells