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Pathological Processes > 4. Healing And Repair > Flashcards

4. Healing And Repair Flashcards

1
Q

What 3 processes are involved in wound healing?

A
  1. Haemostasis
  2. Inflammation
  3. Regeneration/resolution and repair of destroyed structures
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2
Q

What is regeneration?

A

The growth of cells and tissues to replace lost structures with minimal evidence of previous injury.

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3
Q

What type of injury can easily heal by regeneration?

A

Abrasions - superficial and only damage cells from epidermis and dermis

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4
Q

What must be intact for regeneration to take place?

A

Stem cells remain undamaged

Connective tissue scaffold

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5
Q

Which cells replicate to regenerate lost structures, why only these?

A

Stem cells

Terminally differentiated cells can no longer divide

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6
Q

What type of replication do stem cells demonstrate?

A

Assymetric - when they divide, one cell stays as a stem cell and the other differentiates

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7
Q

Where can stem cells be found in skin?

A

Epidermis - basal layer adjacent to the basement membrane

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8
Q

Where can stem cells be found in the GI tract?

A

Bottom of the gastric crypts

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9
Q

What are the 3 different types of stem cells?

A

Unipotent
Multipotent
Totipotent

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10
Q

What are unipotent stem cells?

A

Can only differentiated into one type of cell. E.g epithelia
Most stem cells are unipotent

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11
Q

What is an example of a multipotent stem call?

A

Haematopoietic stem cells - can produce several types of differentiated cell

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12
Q

What is an example of a totipotent stem cell?

A

Embryonic stem cells - can produce any type of cell

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13
Q

Most adult stem cells are ___potent.

A

Unipotent

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14
Q

What are labile tissues?

A

Continuously dividing tissues - in the cell cycle

Short-lived cells

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15
Q

What are examples of labile tissues?

A

Surface epithelia
Haematopoietic tissues
Cells of bone marrow
Columnar epithelia of GI tract

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16
Q

What are stable tissues?

A

Tissues that normally have low level of replication but can undergo rapid proliferation in response to stimuli.

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17
Q

Give examples of stable tissue.

A

Liver parenchymal cells, bone, endothelium of blood vessels.

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18
Q

What are permanent tissues?

A

Cells that are non-dividing. Cannot undergo mitosis as have no/few stem cells.

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19
Q

Give examples of permanent tissues.

A

Skeletal muscle
Cardiac muscle
Neural tissue

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20
Q

What stage of the cell cycle are labile, stable and permanent tissues in?

A

Labile - continuously cycling
Stable - G0, resting but can re-enter
Permanent - left the cell cycle, cannot re-enter

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21
Q

In what circumstances can regeneration take place?

A

If a labile or stable tissue

If not extensive - connective tissue scaffold remains

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22
Q

How will damage to permanent tissues heal?

A

Fibrous repair and scarring

23
Q

What is fibrous repair?

A

Healing with formation of fibrous connective tissue - scar

Healing by secondary intention

24
Q

When does fibrous repair occur?

A

Significant tissue loss - secondary intention
Permanent tissue injured
Ongoing chronic inflammation

25
Q

What processes are involved in fibrous repair?

A
  1. Phagocytosis of necrotic tissue debris
  2. Proliferation of endothelial cells which results in angiogenesis
  3. Proliferation of fibroblasts and myofibrolasts - collagen synthesis and wound contraction
  4. Scar matures and shrinks due to contraction
26
Q

What cells are involved in fibrous repair?

A

Inflammatory cells - phagocytes - engulf debris
Endothelial cells - angiogenesis
Fibroblasts and myofibroblasts - collagen, wound contraction

27
Q

Why are new scars red?

A

Lots of blood vessels still present

28
Q

How do old scars differ to new scars?

A

White - melanocytes do not regenerate
Hairless - hair cells and sweat glands not regenerated
Stretch - fibroblasts lay down collagen but not elastin

29
Q

What are symptoms of scurvy?

A

Unable to heal wounds - tendency to bleed
Tooth loss
Old scars break down and open as fresh wounds

30
Q

What are symptoms of Ehlers-Danlos syndrome?

A

Hyperextensible, fragile skin
Joints hypermobile and prone to dislocation
Would healing poor

31
Q

What are signs of osteogenesis imperfecta?

A

Skeletal fragility
Blue sclera - too little collagen
Hearing impairment and dental abnormalities

32
Q

What defect is present in Alport syndrome?

A

Abnormal Type IV collagen.

Dysfunction of glomerular basement membrane, cochlea of ear and lens of eye

33
Q

What are the signs of alport syndrome?

A

Usually male - X linked
Present with haematuria and progress to chronic renal failure
Neural deafness and eye disorders

34
Q

Which mediators are most important in controlling growth and repair?

A

Growth factors

35
Q

Which genes code for growth factors?

A

Proto-oncogenes

36
Q

What is contact inhibition, how does it differ in regeneration and neoplasia?

A

Isolated cells will replicate until they have cells touching them, when they will stop.
Occurs in wound healing but is altered in malignant cells.

37
Q

What adhesion molecules bind cells to each other?

A

Cadherins

38
Q

Which adhesion molecules bind cells to the EC matrix?

A

Integrins

39
Q

Which wounds will heal by primary intention?

A

incisional, closed, non-infected and sutured wounds.

Epidermis regenerates

40
Q

Outline the process of healing by primary intention.

A
  1. Haemostasis
  2. Inflammation
  3. Migration of cells
  4. Regeneration
  5. Early scarring
  6. Scar maturation
41
Q

What type of wounds will heal by secondary intention?

A

Excisional wounds
Wounds with tissue loss and separated edges
Infected wounds
E.g ulcer, abscess

42
Q

How does healing by secondary intention differ to process of primary intention?

A

More granulation tissue
Larger clot and more debris creates a larger inflammatory reaction.
More wound contraction needed to close space.
Increased scar formation
New epidermis is thinner
Takes longer!

43
Q

Outline how bone heals after a fracture.

A 
Haematoma 
Granulation tissue
Soft callus 
Hard Callus 
Lamellar bone
44
Q

What local factors influence wound healing?

A
  1. Type, size and location of wound
  2. Blood supply
  3. Local infection
  4. Foreign bodies
  5. Protection
45
Q

What systemic factors can influence wound healing?

A
  1. Age
  2. Anaemia, hypoxia and hypovolamia
  3. Obesity - increased tension
  4. Diabetes
  5. Malignancy
  6. Genetic disorders
  7. Malnutrition
  8. Drugs
46
Q

Which type of drug will delay wound healing?

A

Steroids - inhibit collagen synthesis

47
Q

What are the complications associated with fibrous repair?

A

Insufficient fibrosis - hernia, ulceration
Excessive fibrosis - keloid scar
Excessive contraction - obstruction of tubes, joint contractures
Loss of function - MI in myocardium

48
Q

Why doesn’t cartilage heal well?

A

Lacks blood supply, lymphatic drainage or innervation.

49
Q

How do peripheral nerves heal?

A

Axon of severed nerve undergoes wallerian degeneration.
Use vacated schwann cells to guide them back to the tissue that the nerve innervated.
Axon grows approx 1-3mm/day

50
Q

How does central nervous tissue regenerate?

A

Permanent tissue, so when tissue damage occurs in CNS the neural tissue is replaced by proliferation of glial cells.

51
Q

What is a traumatic neuroma?

A

Benign proliferation of a nerve following damage. Forms a nodule during regeneration, very painful.

52
Q

Which people are at higher risk of keloid scar formation?

A

Afro-caribbean

53
Q

What type of tissue can grow to form ‘proud flesh’?

A

Granulation tissue

Pathological Processes (12 decks)

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