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ESA2 > MOD S5 - Healing & Repair > Flashcards

MOD S5 - Healing & Repair Flashcards

0
Q

What are the stages of fibrous repair?

A

Initial inflammation
Granulation tissue
Maturation

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1
Q

What is fibrous repair?

A

-Fibrous repair is the replacement of functional tissue by scar tissue

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2
Q

What is granulation tissue?

A

A combination of capillary loops and myofibroblasts

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4
Q

Describe the initial inflammation stage of fibrous repair

A

Inflammatory cell infiltrate
Blood clot forms
Acute inflammation around edges
Chronic inflammation - macrophages and lymphocytes migrate into clot

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5
Q

Describe what occurs after the initial inflammation stage in fibrous repair

A

-Clot replaced by granulation tissue
-Key components - these initiate fibrous repair by combining to form granulation tissue formation:
>Cell migration
>Blood vessels - angiogenesis
>Extracellular matrix production/remodelling

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9
Q

Describe the maturation stage of fibrous repair

A 
Comparatively long lasting
Cell population falls
Collagen increases, matures and remodels
Myofibroblasts contract, reducing volume of defect
Vessels differentiate and are reduced
Fibrous scar is end result
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10
Q

Describe control of fibrous repair

A

Poorly understood
Inflammatory cells recruited by chemotaxis
Angiogenesis occurs due to angiogenesis cytokines
Fibrosis occurs due to macrophages releasing pro-fibrotic cytokines causing fibroblast proliferation

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11
Q

Describe cell migration in fibrous repair

A 
-Inflammatory cells
>Phagocytosis of debris - macrophages and neutrophils
>Chemical mediators - macrophages and lymphocytes
-Endothelial cells
>Angiogenesis
-Fibroblasts/myofibroblasts
>ECM proteins eg collagen
>Wound contraction
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12
Q

Describe angiogenesis in fibrous repair

A
  • Proangiogenic growth factors eg VEGF induce endothelial proliferation
  • Pre-existing blood vessels sprout new vessels
  • Endothelial proteolysis of basement membrane
  • Migration of endothelial cell by chemotaxis
  • Endothelial maturation and tubular remodelling
  • Recruitment of periendothelial cells
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13
Q

Describe the function of the extracellular matrix

A 
Supports and anchors cells
Separates tissue compartments
Sequesters growth factors
Allows communication between cells
Facilitates cell migration
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14
Q

Describe regeneration

A

The replacement of dead or damaged cells by functional, differentiated cells which originate from stem cells

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15
Q

Briefly describe stem cells

A

Undifferentiated cells which can proliferate to produce either more stem cells in order to maintain the stem cell pool OR produce cells which can differentiate into a specialised cell type

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16
Q

What is the difference between uni potent, toti potent and pluripotent?

A

Uni potent cells can only differentiate into one type of cell eg epithelial cells
Pluripotent cells can differentiate into several types of cell eg haemopoietic cells
Toti potent cells can differentiate into any type of cell eg embryonic cells

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17
Q

Do all cells have the same propensity for regeneration

A

No
Labile cells regenerate fastest
Stable cells regeneration is variable
Permanent cells cannot regenerate

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18
Q

Describe and give an example of labile cells

A

Normal state is active cell division
Usually rapid proliferation
Eg epithelial or heamatopoietic cells

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19
Q

Describe and give an example of stable cells

A

Normal state is G0 so not active division
Variable speed of proliferation
Eg hepatocytes, osteoblasts, fibroblasts

20
Q

Describe and give an example of permanent cells

A

Unable to divide
Unable to regenerate
Eg neurones, cardiac monocytes

21
Q

What factors control regeneration?

A

Growth factors

Contact between basement membranes and adjacent cells

22
Q

How do growth factors control regeneration?

A

Promote proliferation of stem cell population
Promote expression of genes controlling cell cycle
Hormones (oestrogen, testosterone, growth hormone)
Autocrine, paracrine and endocrine

23
Q

How does contact between basement membranes and adjacent cells control regeneration?

A

Signalling through adhesion molecules
Inhibits proliferation in intact tissue by contact inhibition
Loss of contact promotes proliferation
Exploited in cancer

24
Q

Describe healing by primary intention

A

Incised wound
Apposed edges
Minimal clot/granulation tissue
Epidermis regenerates
Dermis undergoes fibrous repair
Sutures out at 5-10 days. ~10% of normal strength
Maturation of scar continues up to two years
Minimal contracture and scarring, good strength
Risk of trapping infection/abcess

25
Q

Describe healing by secondary intention

A

Infarct, ulcer, abscess or any large wound
Quantitative differences:
Unapposed wound edges
Large clot dries to form clot
Epidermis regenerates from the base upwards
Repair process produced a large amount of granulation tissue
Takes a long time to heal completely

26
Q

Compare healing by primary and secondary intention

A

1ary is a small, clean wound whereas 2ndary is larger
2ndary produces much more granulation tissue
2ndary has more contraction to reduce the volume of the defect
2ndary leaves a larger (but not necessarily weaker) scar
2ndary takes longer to heal than 1ary

27
Q

Discuss local factors affecting the efficacy of healing and repair

A

Type, size & location of wound
Apposition, lack of movement (skin/bone/nerve damage)
Blood supply (arterial & venous)
Infection (systemic, gangrenous)
Foreign material (dirt, glass, sutures, necrotic tissue)
Radiation damage

28
Q

Discuss general factors affecting the efficacy of healing and repair

A

Age
Drugs (eg steroids) and hormones
General dietary deficiencies eg protein
Specific dietary deficiencies eg vitamin c, amino acid
General state of health (chronic diseases eg diabetes)
General cardiovascular status

29
Q

What may be a complication/failing of healing in cardiac muscle?

A

Fibrosis occurs

Aka functional muscle cells are replaces by non-contracting non-conducting scar tissue

30
Q

What is a special aspect of healing in bone

A

Callus formed

Read up on this - see TOB

31
Q

What is a special aspect of healing in the liver?

A

In chronic damage, cirrhosis occurs
In cirrhosis, hepatocytes retain some ability to regenerate but liver architecture is gone
This leads to nodules of regenerating hepatocytes surrounded by fibrotic scarring
Note: in acute damage regeneration occurs

32
Q

What is a special aspect of healing in peripheral nerves?

A

Wallerian degeneration

Proximal degeneration, distal proliferation (~1mm/day)

33
Q

What is a special aspect of healing in the CNS?

A

No regenerative capacity

Glial cells can regenerate (Gliosis)

34
Q

What is a special aspect of healing in skeletal muscle

A

Limited regeneration capacity due to satellite cells

35
Q

What is a special aspect of healing in smooth muscle cells?

A

Smooth muscle is a permanent tissue so will be replaced with scar tissue
NB vascular smooth muscle has some limited regeneration ability

ESA2 (39 decks)

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