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USMLE Pathology > Wound Healing > Flashcards

Wound Healing Flashcards

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USMLE® Step 1 flashcards
1
Q

What is regeneration?

A

Damaged tissue replaced with native tissue

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2
Q

What are the 3 ways tissues can be divided in terms of their regenerative capacity?

A
  • Labile tissues - continuously cycle to regenerate tissue
  • Stable tissues - quiescent but can reenter cell cycle
  • Permanent tissues - lack regenerative potential
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3
Q

What are examples of labile tissues (continuously cycle to regenerate tissue)?

A
  • Small and large bowel (stem cells in mucosal crypts)
  • Skin (stem cells in basal layer)
  • Bone marrow (hematopoietic stem cells)
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4
Q

What are bone marrow stem cells cluster of differentiation +ve?

A

CD34+

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5
Q

What is an example of a stable tissue that can reenter cell cycle?

A

Liver
- each hepatocyte can renter cell cycle

PCT of kidney

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6
Q

What are examples of permanent tissues? (lack regenerative potential)

A
  • Myocardium
  • Skeletal muscle
  • Neurons
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7
Q

What is repair as opposed to regeneration?

A

Repair replaces damaged tissue with fibrous scar
- Occurs when regenerative stem cells are lost (e.g. scar deep enough to damage basal layer) or when tissue lacks regenerative capacity (permanent tissues)

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8
Q

What is the initial phase of repair of a scar?

A

Formation of granulation tissue

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9
Q

What are the 3 components of granulation tisssue?

A
  • Fibroblasts (deposit T3 collagen)
  • Capillaries (provide nutrients)
  • Myofibroblasts (contract wound)
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10
Q

What is type 3 collagen replaced with in a scar?

A

Type 1

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11
Q

What enzyme removes type 3 collagen?

What does it require as a cofactor?

A

Collagenase

- Requires zinc as a cofactor

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12
Q

Where can T3 collagen be found?

A
  • Blood vessels
  • Granulation tissue
  • Embryonic tissue
    V. pliable
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13
Q

Where is T4 collagen seen?

A

BM

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14
Q

What type of collagen is initially deposited in a scar and what is it then replaced with?

A

Type 3 collagen, replaced with type 1

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15
Q

What is TGF-alpha a growth factor for?

A

Epithelium and fibroblast

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16
Q

What is TGF-B a growth factor for?

A

Fibroblast growth factor; inhibits inflammation

17
Q

What is PDGF a growth factor for?

A
  • Endothelium
  • SM
  • Fibroblast growth factor
18
Q

What is FGF a growth factor for?

A
  • Angiogenesis

- Skeletal development

19
Q

What is VEGF a growth factor for?

A

Angiogenesis

20
Q

What are the 2 mechanisms through which cutaneous healing can occur?
Describe them

A

Primary or secondary intention

Primary
- Wound edges brought together; minimal scar formation

Secondary
- Edges are not approximated; granulation tissue fills in the defect

21
Q

What are causes of delayed wound healing outside of infection?

A
  • Vit C (hydroxylation)
  • Copper (lysyl oxidase - involved in cross linking
  • Zinc deficiency
  • Foreign body
  • Ischemia
  • Diabetes
  • Malnutrition
22
Q

What amino acids make up collagen?

A
  • Glycine
  • Proline
  • Lysine
23
Q

What does Vit C do to collagen?

A

Hydroxylates proline or lysine

- Allows cross linking between collagen molecules

24
Q

What does zinc do in scar formation?

A

Cofactor for collagenase which removes type 3 replaces with type 1

25
Q

How can copper deficiency affect wound healing?

A

Require for formation of :

- Lysyl oxidase - involved in cross linking collagen molecules

26
Q

What is dehiscence ?

When does it commonly occur?

A

Rupture of wound - most commonly seen after abdo surgery

27
Q

What is a hypertrophic scar?

A

Excess production of scar tissue localized to wound

28
Q

What is a keloid and what is it due to?

A
  • Excess production of scar tissue that is out of proportion to the wound
  • Characterised by excess type 3 collagen
29
Q

What group is more likely to get keloid?

A

African Americans

30
Q

Where does keloid typically affect?

A

Earlobes, face and upper extremities

USMLE Pathology (15 decks)

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