Chapter 14: Wound Healing Flashcards

1
Q

Wound healing: days 1-10

A

Inflammation: PMNs, macrophages

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2
Q

Rate of epithelialization during wound healing

A

1-2 mm/day

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3
Q

Wound healing: 5 days - 3 weeks

A

Proliferation: fibroblasts, collagen deposition, neovascularizaiton, granulation tissue formation; type 3 collagen replaced with type 1

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4
Q

Wound healing: 3 weeks - 1 year

A

Decreased vascularity

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5
Q

What happens during the remodeling phase of wound healing?

A

Net amount of collagen does not change with remodeling, although significant production and degradation occur. Collagen cross-linking occurs.

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6
Q

Rate of regeneration of peripheral nerves

A

1 mm/day

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7
Q

Order of cell arrival in wound

A

Platelets, PMNs, Macrophages, Lymphocytes, (recent research shows arrival before fibroblasts), fibroblasts

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8
Q

Essential for wound healing (release of growth factors, cytokines, etc)

A

Macrophages

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9
Q

Chemotactic for macrophages; anchors fibroblasts

A

Fibronectin

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10
Q

Replace fibronectin-fibrin with collagen

A

Fibroblasts

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11
Q

Predominant cell type by day:

  • Days 0-2
  • Days 3-4
  • Days 5 and on
A
  • Days 0-2: PMNs
  • Days 3-4: Macrophages
  • Days 5 and on: fibroblasts
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12
Q

What comprises platelet plug?

A

Platelets and fibrin

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13
Q

What comprises the provisional matrix?

A

Platelets, fibrin, fibronectin

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14
Q

Definition: accelerated wound healing

A

Reopening a wound results in quicker healing the 2nd time (as healing cells are already present there)

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15
Q

Most important factor in healing open wounds (secondary intention)

A

Epithelial integrity

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16
Q

What does secondary intention wound healing depend on?

A
  • Epithelial integrity.

- Migration from hair follicles (#1 site), wound edges, sweat glands. Dependent on granulation tissue in wound.

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17
Q

Unepithelialized wounds leak…

A

Serum and protein, promote bacteria.

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18
Q

Most important factor in healing closed incisions (primary intention)

A

Tensile strength

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19
Q

What does tensile strength / primary intention depend on?

A

Depends on collagen deposition and cross-linking of collagen

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20
Q

Strength layer of bowel

A

Submucosa

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21
Q

Weakest time point for small bowel anastomosis

A

3 - 5 days

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22
Q
  • Smooth muscle cell-fibroblast; communicate by gap junctions
  • Involved in wound contraction and healing by secondary intention
  • Perineum has better wound contraction than leg
A

Myofibroblasts

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23
Q

Collagen: MC type of collagen; skin, bone, tendons. Primary collagen in a healed wound.

A

Type 1

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24
Q

Collagen: Cartilage

A

Type 2

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25
Collagen: increased in healing wound, also in blood vessels and skin
Type 3
26
Collagen: Basement membrane
Type 4
27
Collagen: widespread, particularly found in the cornea
Type 5
28
Required for hydroxylation (prolyl hydroxylase) and subsequent cross-linking of proline residues in collagen
Alpha-ketoglutarate, vitamin C, oxygen, and iron
29
Collagen: every third amino acid
Proline
30
What does proline cross-linking do?
Improves wound tensile strength
31
Vitamin C deficiency
Scurvy
32
% tensile strength to pre-wound strength
80%
33
Predominant collagen type synthesized for days 1-2
Type 3 collagen
34
Predominant collagen type synthesized by days 3-4
Type 1 collagen
35
When is type 3 collagen replaced with type 1 collagen?
By 3 weeks
36
When does the wound reach maximum tensile strength?
At 8 weeks.
37
When is maximum collagen accumulation?
2-3 weeks. After that the amount of collagen stays the same, but continued cross-linking improves strength.
38
Inhibits collagen cross-linking
d-Penicillamine
39
Essentials for wound healing
- Moist environment (avoid desiccation) - Oxygen delivery - Avoid edema - Remove necrotic tissue
40
How do you optimize oxygen delivery for wound healing?
Optimize fluids, no smoking, pain control, arterial revascularlization, supplemental oxygen.
41
What do you want transcutaneous oxygen to measure for wound healing?
Want transcutaneous oxygen measurement (TCOM) > 25 mm Hg
42
Impediments to wound healing
Bacteria > 10^5, devitalized tissue and foreign bodies, cytotoxic drugs, diabetes, albumin
43
How does bacteria 10^5 impede wound healing?
Decreased oxygen content, collagen lysis, prolonged inflammation
44
How does devitalized tissue and foreign bodies impede wound healing?
Retards granulation tissue formation and wound healing.
45
How do cytotoxic drugs impede wound healing?
5FU, methotrexate, cyclosporine, FK-506, etc can impair wound healing in first 14 days after injury
46
How can diabetes impede wound healing?
Can contribute to poor wound healing by impeding the early-phase inflammation response (hyperglycemia causes poor leukocyte chemotaxis)
47
How do steroids impede wound healing?
Inhibit macrophages, PMNs, and collagen synthesis by fibroblasts; decreases wound tensile strength as well
48
Counteracts effects of steroids on wound healing
Vitamin A (25,000 IU qd)
49
What can cause wound ischemia (hypoxia)?
Fibrosis, pressure (sacral decubitus ulcer, pressure sores), poor arterial inflow (atherosclerosis), poor venous outflow (venous stasis), smoking, radiation, edema, vasculitis
50
Diseases associated with abnormal wound healing
Osteogenesis imperfecta, Ehlers-Danlos syndrome, Marfan's, Epidermyolsis bullosa, Scurvy, Pyoderma Gangrenosum
51
Common location of diabetic foot ulcer
Charcot's joint (2nd MTP joint) secondary to neuropathy
52
90% due to venous insufficiency. | - Tx: Unna boot
Leg ulcers
53
What do scars contain?
A lot of proteoglycans, hyaluronic acid and water.
54
When can you revise a scar?
Wait for 1 year to allow maturation; may improve with age. | - Infants heal with little to no scarring.
55
Contains no blood vessels (get nutrients and oxygen by diffusion)
Cartilage
56
Has no effect on wound healing
Denervation
57
Has no effect on wound healing after 14 days
Chemotherapy
58
Autosomal dominant, dark skinned - Collaged goes beyond original scar - Tx: intra-lesion steroid injection; silicone, pressure garments, XRT
Keloids
59
Dark skinned; flexor surfaces of upper torso - Collagen stays within confines of original scar - Often occurs in burns or wounds that take a long time to heal - Tx: steroid injection, silicone, pressure garments
Hypertrophic scar tissue
60
What are contained in alpha granules of platelets?
- Platelet factor 4: aggregation - Beta-thrombomodulin: binds thrombin - Platelet-derived growth factor (PDGF): chemoattractant - Transforming growth factor beta (TGF-beta): modulates above responses
61
What do dense granules of platelets contained?
Contain adenosine, serotonin, and calcium
62
Platelet aggregation factors
TXA2, thrombin, platelet factor 4