Session 4-Healing:Regeneration And Repair

Question 1

Which processes are involved in wound healing? (3)

Answer 1

1) Haemostasis
2) Inflammation
3) Regeneration and repair

Question 2

What is regeneration?

Answer 2

Restitution with no, or minimal, evidence that there was a previous injury

Question 3

What is the difference between an abrasion and an ulcer?

Answer 3

Abrasion-lose top few layers of cells, only affecting mucosa

Ulcer-injury goes into submucosa, more severe form of abrasion

Question 4

Which cells replicate in regeneration?

Answer 4

New differentiated cells are mainly derived from stem cells

Question 5

What are stem cells?

Answer 5

Prolonged proliferative activity and show asymmetric replication

Question 6

Whereabouts in the epidermis are the stem cells?

Answer 6

Basal layer adjacent to basement membrane

Question 7

Whereabouts in the intestinal mucosa are the stem cells?

Answer 7

Bottom of crypts

Question 8

Whereabouts in the liver are the stem cells?

Answer 8

Between hepatocytes and bile ducts

Question 9

What are the three types of stem cells?

Answer 9

1) unipotent
2) multipotent
3) totipotent

Question 10

What are unipotent stem cells?

Answer 10

Most adult stem cells which only produce one type of differentiated cell eg. Epithelia

Question 11

What are multipotent stem cells?

Answer 11

Produce several types of differentiated cell eg haematopoeitic stem cells

Question 12

What are totipotent stem cells?

Answer 12

Embryonic stem cells which can produce any type of cell and therefore any tissues of the body

Question 13

What are blood cells derived from?

Answer 13

Multipotent stem cells in bone marrow

Question 14

Can all tissues regenerate?

Answer 14

No

Question 15

Give examples of labile tissues and describe what they contain

Answer 15

Surface epithelia, haematopoeitic tissues

Contain short-lived cells that are replaced from cells derived from stem cells

Question 16

Give examples of stable tissues

Answer 16

Liver parenchyma
Bone
Fibrous tissue
Endothelium

Question 17

True or false: stable tissues have a low level of replication but if necessary can undergo rapid proliferation

Answer 17

TRUE

Question 18

Give examples of permanent tissues

Answer 18

Neural tissue
Skeletal muscle
Cardiac muscle

Question 19

Which type of cells are continuously cycling in the cell cycle?

Answer 19

Labile cells

Question 20

In what circumstances can regeneration take place?

Answer 20

If damage occurs in labile or stable tissue

If tissue damage is not extensive

Question 21

What is fibrous repair?

Answer 21

Healing with formation of fibrous connective tissue (scar)

Question 22

When does fibrous repair occur?

Answer 22

With significant tissue loss and if permanent or complex tissue is injured

Question 23

Which type of injury is repaired by regeneration?

Answer 23

Necrosis of labile or stable tissues if collagen framework is intact

Question 24

Which injuries involve fibrous repair?

Answer 24

Necrosis of labile or stable tissues when collagen framework is destroyed or when there is ongoing chronic inflammation

OR

Necrosis of permanent tissues

Question 25

During which period of scarring are stitches removed from wounds?

Answer 25

Between 7 and 10 days (early scarring)

Question 26

When does granulation tissue form?

Answer 26

3 days

Question 27

What does granulation tissue consist of?

Answer 27

Developing capillaries Fibroblasts and myofibroblasts Chronic inflammatory cells

Question 28

What are the functions of granulation tissue?

Answer 28

Fills the gap Capillaries supply oxygen, nutrients and cells Contracts and closes the hole

Question 29

What are the stages of scar formation? (6)

Answer 29

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

Question 30

Which inflammatory cells are involved in fibrous repair?

Answer 30

1) Neutrophils and macrophages-phagocytosis | 2) Lymphocytes and macrophages-production of chemical mediators

Question 31

How are endothelial cells involved in fibrous repair?

Answer 31

They proliferate and result in angiogenesis

Question 32

How are fibroblasts and myofibroblasts involved in fibrous repair?

Answer 32

1) Produce extracellular matrix proteins eg collagen | 2) Responsible for wound contraction-contraction of fibrils within myofibroblasts

Question 33

Why do scars become white?

Answer 33

No regeneration of melanocytes

Question 34

Why do scars tend to stretch with time?

Answer 34

Fibroblasts/myofibroblasts cannot lay down elastin

Question 35

Why does hair not grow on a scar?

Answer 35

Hair follicles cannot regenerate

Question 36

Which type of collagen is the most common and where is it found?

Answer 36

Type I | In hard and soft tissue (bones, tendons, ligaments, skin, sclera, cornea, blood vessels)

Question 37

What does type IV collagen make up?

Answer 37

Basement membrane

Question 38

Where are the polypeptide alpha chains of collagen synthesised?

Answer 38

In the ER of fibroblasts and myofibroblasts

Question 39

Which vitamin is needed for hydroxylation in collagen formation?

Answer 39

C

Question 40

What produces the tensile strength of collagen?

Answer 40

Cross-linking between molecules

Question 41

What causes scurvy?

Answer 41

Vitamin C deficiency

Question 42

Which collagen does scurvy affect most?

Answer 42

Collagens supporting blood vessels

Question 43

Why can scurvy lead to tooth loss?

Answer 43

Collagen in periodontal ligament has short half life and normal collagen is replaced by defective collagen

Question 44

What is Ehlers-Danlos syndrome a defect in?

Answer 44

Conversion of procollagen to tropocollagen

Question 45

Why can skin recoil in Ehlers-Danlos syndrome?

Answer 45

Elastic fibres are normal, just missing the tethering effect of normal collagen fibres

Question 46

Describe the joints of a patient with Ehlers-Danlos syndrome

Answer 46

Hypermobile | Predisposition to joint dislocation

Question 47

Why do patients with osteogenesis imperfecta have blue sclerae?

Answer 47

Too little collagen within them and they are translucent

Question 48

True or false: Alport syndrome is an X-linked disease

Answer 48

TRUE

Question 49

What abnormality results in Alport syndrome?

Answer 49

Type IV collagen abnormality

Question 50

How does Alport syndrome present in children/adolescents?

Answer 50

Haematuria progressing to renal failure Neural deafness Eye disorders

Question 51

Why are growth factors important?

Answer 51

Wound healing

Question 52

What are growth factors coded by?

Answer 52

Proto-oncogenes

Question 53

What do growth factors do in the cell cycle?

Answer 53

Bind to specific receptors, stimulate transcription of genes that regulate entry of cell into cell cycle and cell's passage through it

Question 54

Apart from cell proliferation, what other effects can growth factors have?

Answer 54

``` Inhibition of division Locomotion Contractility Differentiation Viability Activation Angiogenesis ```

Question 55

Which cells produce growth factors?

Answer 55

Platelets Macrophages Endothelial cells

Question 56

What is contact inhibition?

Answer 56

1) signalling through adhesion molecules | 2) inhibits proliferation in intact tissue, promotes proliferation in damaged tissues

Question 57

What do cadherins do?

Answer 57

Bind cells to each other

Question 58

What do integrins do?

Answer 58

Bind cells to extracellular matrix

Question 59

Describe the type of wound in primary intention

Answer 59

Incised, closed and non-infected and sutured wounds (typical surgical wound)

Question 60

What is healing by primary intention?

Answer 60

Disruption of basement membrane continuity but death of only small number of epithelial and connective tissue cells

Question 61

True or false: there is minimal clot and granulation tissue in primary intention

Answer 61

TRUE

Question 62

What occurs in healing by primary intention?

Answer 62

1) epidermis regenerates 2) dermis undergoes fibrous repair 3) minimal contraction and scarring

Question 63

Describe the type of wound in secondary intention

Answer 63

Excisional wound, wounds with tissue loss and separated edges, infected wounds eg infarct, ulcer, abscess

Question 64

What happens to the wound in secondary intention?

Answer 64

Open wound filled by abundant granulation tissue - grows in from wound margins

Question 65

True or false: circular scars heal better than rectangular ones

Answer 65

FALSE - other way round

Question 66

True or false: healing by primary intention takes longer than healing be secondary intention

Answer 66

FALSE - secondary takes longer

Question 67

Which local factors can influence wound healing? (5)

Answer 67

1) type, size and location of wound 2) mechanical stress 3) blood supply 4) local infection 5) foreign bodies

Question 68

Which general factors influence wound healing?

Answer 68

1) age 2) anaemia, hypoxia and hypovolaemia 3) obesity 4) diabetes 5) genetic disorders 6) drugs 7) vitamin deficiency 8) malnutrition

Question 69

What are the complications of fibrous repair? (6)

Answer 69

1) insufficient fibrosis 2) formation of adhesions 3) loss of function due to replacement of specialised functional parenchymal cells by scar tissue 4) disruption of complex tissue relationships within an organ 5) overproduction of fibrous scar tissue 6) excessive scar contraction

Question 70

What is a keloid scar?

Answer 70

Lots of collagen within the dermis so excessive fibrous scar tissue is produced