Regeneration and Repair

Question 1

What processes are involved with wound healing?

Answer 1

Haemostasis - vessels are open
Inflammation - tissue injury
Rgeneration/repair - injured/destroyed structures

Question 2

What is regeneration?

Answer 2

Restitution with no or minimal evidence that there was previous injury
- healing by primary intention

Question 3

What are stem cells?

Answer 3

Undifferentiated cells with proliferative activity

Able to replace damaged/lost cells

Question 4

Where are stem cells?

Answer 4

Epidermis - basal layer next to basement membrane

Intestinal mucosa - bottom of crypts

Liver - between hepatocytes and bile ducts

Question 5

What are the types of stem cells?

Answer 5

Unipotent

• most adult stem clls
• one type of differentiated cell

Multipotent
- produce several types of differentiated cell

Totipotent

• embryonic stem cells
• produce any type of cell

Question 6

What types of tissue are there?

Answer 6

Labile
Stable
Permanent

Question 7

What are labile tissues?

Answer 7

Short lived cells
Replaced by stem cells

e.g. epithelia

Question 8

What are stable tissues?

Answer 8

Low level of replication
Can undergo rapid proliferation to repair damage

e.g. liver, bone

Question 9

What are permanent tissues?

Answer 9

Nature cells cannot undergo mitosis
Few stem cells

e.g. cardiac muscle, neural tissue

Question 10

What is fibrous repair?

Answer 10

Healing with formation of fibrous connective tissue - scar

- healing by secondary intention

Question 11

When does fibrous repair occur?

Answer 11

Significant tissue loss

Permanent tissue injured

Question 12

How does a scar form?

Answer 12

1. haemostasis
2. acute inflammation
3. chronic inflammation
4. granulation tissue forms
5. early scar
6. scar maturation

Question 13

What is granulation tissue?

Answer 13

Tissue with a granular appearance and texture

Question 14

What does granulation tissue consist of?

Answer 14

Developing capillaries
Fibroblasts
Myofibroblasts
Chronic inflammatory cells

Question 15

What are the functions of granulation tissue?

Answer 15

Fills the gap

Capillaries supply oxygen , nutrients and cells

Contracts and closes the hole

Question 16

What are the stages of fibrous repair?

Answer 16

1. blood clots
2. neutrophils infiltrate and digest clot
3. macrophages and lymphocytes are recruited
4. vessels sprout, myo/fibroblasts make glycoproteins
5. vascular network, collagen synthesised, macrophages reduced
6. maturity, cells much reduced, collagen matures, contracts and remodels

Question 17

What cells are involved in fibrous repair?

Answer 17

Inflammatory cells

• neutrophils
• macrophages
• lymphocytes

Endothelial cells

Fibroblasts
Myofibroblasts

Question 18

What is collagen?

Answer 18

Provides extracellular framework

Type 1 - found in hard and soft tissues
Type 4 - makes up basement membranes

Question 19

How is collagen synthesised?

Answer 19

α synthesised in ER of fibroblasts and myofibroblasts
Enzymatic modification including vitamin C dependent hydroxylation
α chains cross link to form procollagen triple helix
Procollagen secreted and cleaved to tropocollagen
Tropocollagen polymerises to form microfibrils and fibrils of collagen

Question 20

What condition are a result of defective collagen synthesis?

Answer 20

Acquired
-scurvy

Inherited

• Ehlers-Danlos syndrome
• osteogenesis imperfecta
• Alport syndrome

Question 21

What is scurvy?

Answer 21

Vitamin C deficiency

Inadequate vitamin C dependent hydroxylation of procollagen α chains
Reduced cross-linking

Unable to heal wounds
Old scars breakdown and open up as fresh wounds

Question 22

What is Ehlers-Danlos syndrome?

Answer 22

Defective conversion of procollagen to tropocollagen

Fibres lack tensile strength
Poor wound healing

Hypermobile joints
Hyperextensible skin

Question 23

What is osteogenesis imperfecta?

Answer 23

Brittle bone disease

Too little bone tissue - skeletal fragility

Blue sclera - little collagen in them

Question 24

What is Alport syndrome?

Answer 24

X-linked disease

Type 4 collagen abnormal

Question 25

How is regeneration and repair controlled?

Answer 25

Cell signalling

• hormones
• local mediators (growth factors)
• direct cell-cell contact

Question 26

What are growth factors?

Answer 26

Bind to specific receptors

Stimulate transcription of genes that regulate entry of cell into cell cycle

Question 27

What is healing by primary intention?

Answer 27

Incised, closed wounds
Disruption of basement membrane but only small cell death
Minimal clot and granulation tissue

Question 28

What occurs in healing by primary intention?

Answer 28

Epidermis regnerates
Dermis undergoes fibrous repair
Minimal contraction and scarring

Question 29

What is healing by secondary intention?

Answer 29

Excisional wound
Wound with tissue loss
Infected wounds
Wounds with granulation tissue

Question 30

What occurs in healing by secondary intention?

Answer 30

Epidermis regnerates
Dermis undergoes fibrous repair
Consideral wound contraction
Scar formation

Question 31

How does bone heal?

Answer 31

Haematoma - fills gap and surrounds injury
Granulation tissue forms - cytokine activate osteoprogenitor cells
Soft callus - fibrous tissue and cartilage in which woven bone forms
Hard callus
Lamellar bone - replaces woven bone

Question 32

Local factors affecting wound healing

Answer 32

Type, size, location of wound 
Mechanical stress
Blood supply 
Local infection 
Foreign bodies

Question 33

General factors affecting wound healing

Answer 33

Age
Obesity 
Diabetes
Genetic disorders
Malnutrition

Question 34

Complications of fibrous repair

Answer 34

Insufficient fibrosis

• wound dehiscence
• hernia

Formation of adhesions

Loss of function

Overproduction of scar tissue
- keloid scar