*UNFINISHED* MOD Session 4

Question 1

Define regeneration?

Answer 1

Replacement of dead or damaged cells by functional, differentiated cells

Question 2

What are the daughter cells of a stem cell?

Answer 2

1) Stem cell

2) Specialised cell

Question 3

Define unipotent, pluripotent and totipotent?

Answer 3

1) Can only produce one type of differentiated cell e.g. epithelia
2) Can produce several types of differentiated cell e.g. haematopoietic
3) Can produce any type of cell i.e. embryonic stem cells

Question 4

What are labile cells?

Answer 4

E.g. epithelia or haematopoietic cells
Normal state is active cell division : G1-M-G2
Usually rapid proliferation

Question 5

What are stable cells?

Answer 5

E.g. hepatocytes, osteoblasts, fibroblasts
Resting state G0
Speed of regeneration variable

Question 6

What are permanent cells?

Answer 6

E.g. neurones, cardiac myocytes
Unable to divide - G0
Unable to regenerate

Question 7

How and which growth factors are involved in controlling regeneration?

Answer 7

1) Promote proliferation in the stem cell production
2) Extracellular signals transduced into the cell
3) Promote expression of genes controlling cell cycle
4) Proteins e.g. EGF, PDGF, FGF…
5) Hormones e.g. oestrogen, testosterone, GH

Question 8

How do contact between basement membranes & adjacent cells?

Answer 8

1) Signalling through adhesion molecules
2) Inhibits proliferation in intact tissue
3) ‘Contact inhibition’
4) Loss of contact promotes proliferation

Question 9

What is fibrous repair?

Answer 9

Replacement of functional tissue by scar tissue

Question 10

What is the main type of cell that undergoes fibrous repair when it is necrotic?

Answer 10

Permanent cells (labile and stable undergo either resolution if collagen framework is intact or undergo FR + Sc if collagen is destroyed)

Question 11

What are the three main components of fibrous repair?

Answer 11

1) Cell migration
2) Blood vessels - angiogenesis
3) ECM + remodelling

Initiate fibrous repair by combining to form granulation tissue

Question 12

Describe the three main cell types in fibrous repair?

Answer 12

1) Inflammatory cells
- Phagocytosis of debris - neutrophils, mac

2) Endothelial cells
- Angiogenesis

3) Fibroblasts/Myofibroblasts
- ECM proteins e.g. colagen
- Wound contraction

Question 13

Describe the process of angiogenesis in fibrous repair?

Answer 13

1) Endothelial proteolysis of b.m.
2) Migration of endothelial cell via chemotaxis
3) Endothelial proliferation via VEGF
4) Endothelial maturation and tubular remodelling
5) Recruitment of periendothelial cells

Question 14

Describe the role of the ECM in fibrous repair?

Answer 14

1) Supports and anchors cells
2) Separates tissue compartments e.g. b.m
3) Sequesters GFs
4) Allows communication between cells
5) Facilitates cell migration

Question 15

Describe the 1st process of fibrous repair?

Answer 15

1) Inflammatory cell infiltrate
- blood clot forms
- A.I. around edges
- C.I. : macrophages and lymphocytes migrate into the clot

Question 16

Describe the 2nd process of fibrous repair?

Answer 16

2) Clot replaced by granulation tissue
- angiogenesis - capillaries and lymphatics sprout and infiltrate
- myo/fibroblasts migrate and differentiate
- ECM is produced by myo/fibroblasts

(over time vascularity decreases and [ECM] increases)

Question 17

Describe the 3rd process of fibrous repair?

Answer 17

3) Maturation
- comparatively long-lasting
- cell population falls
- collagen increases, matures and remodels
- myofibroblasts contract and reduce volume of defect
- vessels differentiate and are reduced
- left with fibrous scar

Question 18

What is healing by primary intention?

Answer 18

1) Incised wound
2) Apposed edges
3) Minimal clot and granulation tissue
4) Epidermis regenrates
5) Dermis undergoes fibrous repair
6) Sutures out at ~10 days: approx. 10% normal strength.
7) Transition from granulation tissue to scar tissue
8) Maturation of scar continues up to 2 years
9) Minimal contraction & scarring, good strength
10) Risk of trapping infection - abcess

Question 19

What is healing by secondary intention?

Answer 19

1) Infarct, ulcer, abcess or any large wound
2) Quantitative differences:
- unapposed wound edges
- large clot dries to form a ‘scab’ or ESCHAR
- epidermis regenrates from the base up
- repair process produces much more GRANULATION TISSUE

Question 20

Give differences between secondary intention and primary intention healing?

Answer 20

1) Produces more contraction to reduce volume of defect
2) Produces a larger scar; not necessearily weaker
3) Takes longer

Question 21

What local factors influence wound healing?

Answer 21

1) Type, size, location of wound
2) Apposition, lack of movement&raquo_space;> skin wounds, bone fractures, severed nerves
3) Blood supply : Arterial, Venous
4) Infection: Suppuration, gangrene, systemic
5) Foreign material: dirt, glass, sutures, necrotic tissue
6) Radiation damage

Question 22

What general factors influence wound healing?

Answer 22

1) Age
2) Drugs and hormones
3) General dietary deficiencies e.g. protein
4) Specific dietary deficiencies
- Vit C for collagen OH
- essential AAs
5) General state of health
- chronic diseases e.g. diabetes, RA etc.
6) General CV health

Question 23

What are 3 complications of repair?

Answer 23

1) Insufficient fibrosis
- wound dehiscence; hernia; ulceration
- obesity, elderly, malnutrition, steroids etc

2) Excessive fibrosis
- cosmetic scarring; keloid; cirrhosis; lung fibrosis

3) Excessive contraction
- obst. of tubes & channels (strictures)
- limitation of joint (contractures)