14 Wound Healing Flashcards

1
Q

what are the phases of wound healing?

A

inflammation, proliferation, remodeling

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2
Q

how long dose inflammation last?

A

1-10d

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3
Q

what happens during inflammation?

A

pmns, macrophages, epithelialization

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4
Q

how fast does epithelialization work?

A

1-2mm/d

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5
Q

how long does proliferation last?

A

5d-3weeks

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6
Q

what happens during proliferation?

A

fibroblasts, collagen deposition, neovascularization, granulation tissue formation, type III collagen replaced w type I

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7
Q

how long does remodeling last?

A

3w to 1 yr

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8
Q

what happens to vascularity during remodeling?

A

decreased vascularity

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9
Q

what happens during remodeling?

A

collagen cross-linking occurs

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10
Q

does the amount of collagen increase or stay the same during remodeling?

A

net amount doesn’t change but significant production and degradation occur

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11
Q

how fast do peripheral nerves regenerate?

A

1mm/d

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12
Q

what is the order of cell arrival in a wound?

A

platelets, PMNs, macrophages, lymphocytes, fibroblasts

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13
Q

illustrate timeline of phases of wound healing with dominant cell types and major physiologic events

A

http://cl.ly/image/1R0L3o3L3a0Y

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14
Q

what do macrophages do?

A

essential for wound healing: release growth factors, cytokines, etc.

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15
Q

what does fibronectin do?

A

chemotactic for macrophages; anchors fibroblasts

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16
Q

what do fibroblasts do?

A

replace fibronectin-fibrin with collagen

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17
Q

list the prominent cell type by day.

A

day 0-2: PMNs
days 3-4: macrophages
days 5 and on: fibroblasts

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18
Q

what is a platelet plug consisted of?

A

platelets and fibrin

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19
Q

what does a provisional matrix consist of?

A

platelets, fibrin, fibronectin

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20
Q

what is 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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21
Q

what is the most important factor in healing open wounds (secondary intention)

A

epithelial integrity

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22
Q

what happens to epithelial cells on the skin near open wounds?

A

epithelial cells migrate from hair follicles (#1 site), wound edges, and sweat glands

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23
Q

what is epithelial integrity dependent on?

A

granulation tissue in wound

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24
Q

what happens to unepithelialized wounds?

A

leak serum, protein, promote bacteria

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25
Q

what is the most important factor in healing closed incisions (primary intention)?

A

tensile strength

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26
Q

what does tensile strength depend on?

A

collagen deposition and cross-linking of collagen

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27
Q

what is the strength layer of bowel?

A

submucosa

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28
Q

when is the weakest time point for small bowel anastomosis?

A

3-5d

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29
Q

how do myofibroblasts communicate?

A

gap junctions

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30
Q

what are myofibroblasts called in the smooth muscle cell?

A

fibroblast

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31
Q

what do myofibroblasts do?

A

involved in wound contraction and healing by secondary intention

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32
Q

what has better wound contraction: perineum or leg?

A

perineum

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33
Q

what is the most common type of collagen?

A

I

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34
Q

what is the primary collagen in a healed wound?

A

I

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35
Q

what type of tissue is type I collagen?

A

skin, bone, tendons

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36
Q

what type of tissue is type II collagen

A

cartilage

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37
Q

what collagen type is increased in a healing wound?

A

III

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38
Q

what type of collagen is in blood vessels and skin?

A

III

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39
Q

what type of collagen makes up basement membranes?

A

IV

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40
Q

what type of collagen is widespread?

A

V

41
Q

what type of collagen is particularly found in the cornea?

A

V

42
Q

what is what is required for hydroxylation?

A

alpha-ketoglutarate, vitamin C, oxygen, and iron.

43
Q

what is the enzyme that mediates hydroxylation?

A

prolyl hydroxylase

44
Q

why is hydroxylation needed in wound healing?

A

cross-links proline residues in collagen

45
Q

which amino acid crosslinks in collagen? how often is it in the protein?

A

proline. every 3rd amino acid.

46
Q

what does proline cross linking do?

A

improves wound tensile strength

47
Q

what is scruvy?

A

vitamin C deficiency

48
Q

can tensile strength equal to pre-wound?

A

no. only 80%

49
Q

which types of collagen are predominant at which periods of wound healing?

A

days 1-2: type III

days 3-4: type I collagen

50
Q

when is type III replaced by type I collagen?

A

by 3 weeks of wound healing

51
Q

when does a wound reach max tensile strength?

A

8 weeks

52
Q

when is maximum collagen accumulation reached? what happens after that?

A

2-3 weeks. afterwards, continued cross-linking improves strength

53
Q

what does d-penicillamine do?

A

inhibits collagen cross-linking

54
Q

what are the essentials for wound healing?

A

moist environment, oxygen delivery, avoid edema, remove necrotic tissue

55
Q

how is oxygen delivery to wound maximized?

A

optimize fluids, no smoking, pain control, arterial revascularization, supplemental O2

56
Q

what should transcutaneous oxygen measurement be to maximize wound healing?

A

TCOM > 25mmhg

57
Q

what are impediments to wound healing?

A

bacteria, devitalized tissue, foreign bodies, cytotoxic drugs, diabetes, low albumin, steroids, wound ischemia

58
Q

how is bacteria an impediment to wound healing?

A

decreases oxygen content, collagen lysis, prolonged inflammation

59
Q

how are devitalized tissue and foreign bodies impediments to wound healing?

A

retards granulation tissue formation

60
Q

which cytotoxic drugs are impediments to wound healing and when do they impair wound healing?

A

5FU, methotrexate, cyclosporine, FK-506, etc. impair wound healing in 1st 14 days after injury

61
Q

how does diabetes contribute to poor wound healing?

A

impedes early phase inflammation response (hyperglycemia causes poor leukocyte chemotaxis)

62
Q

how low does albumin need to go before it becomes a risk factor for poor wound healing?

A

<3.0

63
Q

how much bacteria is required before it impedes wound healing?

A

> 10^5/cm^2

64
Q

how do steroids impede wound healing?

A

inhibit macrophages, PMNs, collagen synthesis by fibroblasts. decreases wound tensile strength as well

65
Q

what counteracts effects of steroids on wound healing?

A

vitamin A 25,000 IU qd

66
Q

what causes wound ischemia?

A

hypoxia. caused by fibrosis, pressure (sacral decub, pressure sores), poor arterial inflow (atherosclerosis), poor venous outflow (venous stasis), smoking, radiation, edema, vasculitis

67
Q

what diseases are associated with poor wound healing?

A
osteogenesis imperfecta
ehlers-danlos syndrome
marfan's' syndrome
epidermolysis bullosa
scurvy
pyoderma gangrenosum
68
Q

how is osteogenesis imperfecta associated with abnormal wound healing?

A

type I collagen defect.

69
Q

how is ehlers-danlos syndrome associated with abnormal wound healing?

A

10 types identified, all collagen disorders

70
Q

how is marfan’s syndrome associated with abnormal wound healing?

A

fibrillin defect (connective tissue protein)

71
Q

how is epidermolysis bullosa associated with abnormal wound healing?

A

excessive fibroblasts

72
Q

what is the treatment for epidermolysis bullosa?

A

phenytoin

73
Q

how where do diabetic foot ulcers occur?

A

usually at charcot’s joint secondary to neuropathy, also toes

74
Q

what is charcot’s joint?

A

2nd MTP join

75
Q

what causes leg ulcers?

A

90% due to venous insufficiency

76
Q

what is the treatment for leg ulcers?

A

unna boot (elastic wrap)

77
Q

what do scars contain?

A

lots of proteoglycans, hyaluronic acid, water

78
Q

when do you do scar revisions?

A

wait for one year to allow maturation; may improve with age

79
Q

do infants scar?

A

heal with little or no scarring

80
Q

does cartilage contain blood vessels? how do they get nutrients and O2?

A

no. get nutrients and o2 by diffusion

81
Q

does denervation have any effect on wound healing?

A

no

82
Q

does chemo have any effect on wound healing?

A

not after 14 days

83
Q

who gets keloids?

A

it’s autosomal dominant; dark skinned people

84
Q

what are keloids?

A

collagen goes beyond original scar

85
Q

what is treatment for keloid?

A

intra-lesion steroid injection; silicone, pressure garments, XRT

86
Q

who gets hypertrophic scar tissue?

A

dark skinned

87
Q

where does hypertrophic scar tissue form?

A

flexor surfaces of upper torso

88
Q

how is hypertrophic scar tissue different from keloid?

A

in hypertrophic scar tissue, collagen stays within confines of original scar

89
Q

how do people get hypertrophic scar tissue?

A

often occurs in burns or wounds that take a long time to heal

90
Q

what is the treatment for hypertrophic scar tissue?

A

steroid injection, silicone, pressure garments

91
Q

what are the different platelet granules?

A

alpha and dense granules

92
Q

what are the alpha granules?

A

platelet factor 4, beta-thrombomodulin, PDGF, TGF-beta

93
Q

what does platelet factor 4 do?

A

aggregation

94
Q

what does beta-thrombomodulin do?

A

binds thrombin

95
Q

what does PDGF do?

A

chemoattractant

96
Q

what does TGF-beta do?

A

transforming growth factor beta modulates activity of platelet factor 4, beta-thrombomodulin, and PDGF

97
Q

what do dense granules contain?

A

adenosine, serotonin, calcium

98
Q

what are the paltelet aggregation factors?

A

TXA2, thrombin, platelet factor 4