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ESA 2 - Pathological Processes > Session 4: Healing - Regeneration & Repair > Flashcards

Session 4: Healing - Regeneration & Repair Flashcards

1
Q

What processes are involved in wound healing? (3)

A
  1. Haemostasis
  2. Inflammation
  3. Regeneration and/or repair
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2
Q

What is haemostasis?

A

Stopping of flow of blood

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3
Q

What is regeneration?

A

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

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4
Q

What is an abrasion?

A

Damage to top layer of cells (epidermis)

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5
Q

What is an ulcer?

A

Sever form of abrasion - damage to cells as deep as muscularis mucosae

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6
Q

Which cells replicate in regeneration?

A

Stem cells

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7
Q

What are stem cells?

A

Cells with prolonged proliferative activity and asymmetric replication - mature cell and self-renewal (2 daughter cells)

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8
Q

What are unipotent stem cells? Give an example.

A

Only produce one type of differentiated cell

  • most adult stem cells
  • eg. Epithelia
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9
Q

What are multipotent stem cells? Give an example.

A

Produce several types of differentiated cells

- eg haematopoietic stem cells

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10
Q

What are totipotent stem cells?

Where are they found?

A

Produce any type of cell and therefore any tissues of the body
- embryonic stem cells

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11
Q

What are labile tissues? Give examples.

A

Tissues with short-lived cells that are replaces by cells derived from stem cells
- eg. Surface epithelia, haematopoietic tissues

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12
Q

What are stable tissues? Give examples.

A

Normally low level of replication but if necessary can undergo rapid proliferation
- eg. Liver parenchyma, bone, fibrous tissue, endothelium

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13
Q

What are permanent tissues? Give examples.

A

Mature cells that cant undergo mitosis with few or no stem cells present
- eg. Neural tissues, skeletal muscle, cardiac muscle

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14
Q

When can regeneration occur?

A
  1. Damage to labile or table tissue

2. Not very extensive tissue damage - connective tissue scaffold/collagen still intact

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15
Q

What is fibrous repair?

A

Healing with formation of fibrous connective tissue that results in scarring

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16
Q

When does fibrous repair occur? (3)

A
  1. Necrosis of labile or stable tissues with destroyed collagen framework
  2. Necrosis of labile or stable tissues that leads to on-going chronic
  3. Necrosis of permanent or complex tissue
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17
Q

How does a scar form? (6)

A
  1. Haemostasis
  2. Acute inflammation
  3. Chronic inflammation
  4. Granulation tissue forms
  5. Early scar
  6. Mature scar
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18
Q

How does an early scar differ from a mature scar?

A

Mature scar has less cells and blood vessels, increased collagen

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19
Q

What does granulation tissue consist of? (3)

A
  1. Developing in capillaries
  2. Fibroblasts and myofibroblasts
  3. Chronic inflammatory cells
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20
Q

What are the functions of granulation tissue?

A
  • contract and close the gap
  • provide oxygen, nutrients and cells
  • fills the gap
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21
Q

Which cells are involved in fibrous repair? (3)

A
  1. Inflammatory cells - neutrophils, macrophages, lymphocytes
  2. Endothelial cells
  3. Fibroblasts and myofibroblasts
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22
Q

What is the role of inflammatory cells in fibrous repair? (2)

A
  • phagocytosis of debris: macrophages, neutrophils

- production of chemical mediators: macrophages, lymphocytes

23
Q

What is the role of endothelial cells in fibrous repair?

A

Angiogenesis (growing new blood vessels)

24
Q

What is the role of myo/fibroblasts in fibrous repair?

A
  • produce ECM proteins (collagen)

- wound contraction

25
Q

What happens to the different layers/structures of the skin with scarring? (*hint: think of epidermis, dermis complex structures)

A

Epidermis - regenerated
Dermis - repaired
Complex structures (eg hair follicles, sweat glands) - lost

26
Q

What is collagen?

A

Triple helices of polypeptide alpha chains

27
Q

What are fibrillar collagens?

A

Type I-III responsible for tissue strength

28
Q

What are amorphous collagens?

A

Type IV-VI eg in basement membrane

29
Q

What diseases are the result of defective collagen synthesis? (4)

A
  1. Scurvy
  2. Ehlers-Danlos syndrome
  3. Osteogenesis imperfecta
  4. Alpert syndrome
30
Q

What causes scurvy?

A

Vitamin C deficiency

31
Q

How does vitamin C deficiency affect collagen?

A

Inadequate hydroxylation of procollagen alpha chains leads to reduced cross-linking and defective helix formation
- collagen lacks strength

32
Q

Why does vitamin C deficiency cause scurvy?

A

Defect in collagen particularly affects collagens supporting blood vessels - unable to heal wounds, tendency to bleed

33
Q

What happens in Ehlers-Danlos syndrome?

A
  • Skin is hyperextensible
  • hypermobile joints
  • Defective conversion of procollagen to tropocollagen
  • collagen fibres lack adequate tensile strength although elastic fibres are normal
34
Q

What is osteogenesis imperfecta?

A

Brittle bone disease - too little bone tissue

35
Q

What is Alport syndrome?

A

Type IV collagen abnormal

36
Q

How are regeneration and repair triggered and controlled?

A

Cell to cell signalling

  1. Hormones
  2. Local mediators - growth factors
  3. Direct cell-cell or cell-stroma contact
37
Q

What are growth factors?

A

Local hormone polypeptides that stimulate transcription of genes that regulate entry of cell into cell cycle

38
Q

What is contact inhibition?

A

A regulatory mechanism that functions to keep cells growing into a layer one cell thick (a monolayer)

39
Q

What is the significance of contact inhibition in malignant cells?

A

Contact inhibition is altered and there is disrupted cell-cell adhesion - cells start piling on top of each other

40
Q

How do cells adhere to each other and to ECM?

A

Proteins on cell membranes called adhesion molecules

41
Q

Which adhesion molecules bind cells to each other?

A

Cadherins

42
Q

Which adhesion molecules bind cells to the ECM?

A

Integrins

43
Q

When does healing by primary intention occur?

A

occurs in incisional, closed, non-infected and sutured wounds (clean wounds with opposed edges)

44
Q

Describe the wounds that undergo healing by primary intention.

A

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

45
Q

How does healing by primary intention occur?

A
  • epidermis regenerates: growing new cells creep over denuded cells
  • dermis undergoes fibrous repair
46
Q

What is healing by secondary intention and when does it occur?
Give examples.

A
  • open wound filled by abundant granulation tissue
  • excisional wound
  • wounds with tissue loss and separated edges
  • infected wounds
  • eg. Infarct, ulcer, abscess
47
Q

What occurs in healing by secondary intention?

A
  • same processes as in primary intention but more so
  • considerable wound contraction to close the wound
  • substantial scar formation
48
Q

How does bone heal?

A
  1. Haematoma
  2. Granulation tissue forms
  3. Soft calls
  4. Bony callus
  5. Remodelling
49
Q

What local factors can influence wound healing? (10)

A
  1. Type, size, location of wound
  2. Mechanical stress
  3. Blood supply
  4. Denervation
  5. Local infection/ protection from infection
  6. Foreign bodies
  7. Haematoma
  8. Necrotic tissue
  9. Mechanical stress
  10. Surgical techniques
50
Q

What general factors influence wound healing? (8)

A
  1. Age
  2. Anaemia, hypoxia, hypovolaemia
  3. Obesity
  4. Diabetes
  5. Genetic disorders
  6. Drugs
  7. Vitamin deficiency
  8. Malnutrition
51
Q

What are the complications of fibrous repair? (6)

A
  1. Insufficient fibrosis
  2. Formation of adhesions - fibrotic tissues formed around organ
  3. Loss of function - non-contracting area of myocardium
  4. Disruption of complex tissues relationships within an organ
  5. Overproduction of fibrous scar tissue - keloid scar
  6. Excessive scar contraction - joint contracture (fixed flexures)
52
Q

Comment on the cardiac muscle’s capacity to regenerate.

A

Very limited, if any, regenerative capacity

- MI is followed by scar formation

53
Q

Comment on liver’s capacity to regenerate.

A

Remarkable capacity to regenerate

54
Q

What happens when a nerve is severed?

A

Axons degenerate

  • proximal stumps of degenerated axons sprout and elongate
  • Schwann cells from distal degenerated axons guide them back to tissue

ESA 2 - Pathological Processes (4 decks)

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