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Wound Healing > Wound Healing > Flashcards

Wound Healing Flashcards

1
Q

Wound healing phases

A

inflammation, proliferation, remodeling

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2
Q

Inflammation

A

*days 1-10; PMNs, macrophages; epithelialization 1-2 mm / day

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3
Q

Proliferation

A

*5 days - 3 weeks; fibroblasts, neovascularization, production of collagen, granulation tissue

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4
Q

Remodeling

A
  • 3 weeks to 1 year; type III collagen replaced with type I; decreased vascularity
  • net amount of collagen does not change, although significant production and degradation occur
  • collagen cross-linking occurs
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5
Q

Peripheral nerves

A

regenerate at 1 mm / day

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6
Q

Order of cell arrival in wound

A 
platelets
PMNs
macrophages
fibroblasts
lymphocytes
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7
Q

Macrophages

A

*essential for wound healing (release of growth factors, cytokines)

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8
Q

Fibroblasts

A

replace fibronectin-fibrin with collagen

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9
Q

Fibronectin

A

chemotactic for macrophages; anchors fibroblasts

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10
Q

thrombin and fibrin

A

also act as growth factors for endothelial cells and fibroblasts

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11
Q

Predominant cell type by day

A

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

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12
Q

Platelet plug

A

platelets and fibrin

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13
Q

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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14
Q

Platelet alpha granules

A
  • platelet factor 4 - aggregation
  • beta-thrombomodulin - binds thrombin
  • PDGF - chemoattractant
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15
Q

Platelet dense granules

A

adenosine, serotonin, calcium

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16
Q

Platelet aggregation factors

A

TXA2, thrombin, platelet factor 4

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17
Q

Other factors released from platelets

A
  • platelet activating factor
  • transforming growth factor-alpha
  • fibroblast growth factor
  • beta lysin (antimicrobial)
  • PGE2 and PGI2 (vasodilators)
  • PGF2 (vasoconstriction)
18
Q

Epithelial integrity

A
  • most important factor in healing open wounds (secondary intention)
  • migration from wound edges, sweat glands, hair follicles
  • dependent on granulation tissue
  • unepithelialized wounds leak serum and protein, promote bacteria
19
Q

Tensile strength

A
  • most important factor in healing closed incisions (primary intention)
  • depends on collagen deposition and cross-linking of collagen
  • submucosa - strength layer of bowel
  • weakest time point for small bowel anastomosis: 3-5 days
20
Q

myofibroblasts

A
  • smooth muscle cell-fibroblast, communicate by gap junctions
  • involved in wound contraction and healing by secondary intention
  • perineum has better wound contraction than leg
21
Q

Type I collagen

A

most common type; skin, bone, tendons

*primary collagen in a healed wound

22
Q

Type II collagen

23
Q

Type III collagen

A

increased in healing wound, also in blood vessels and skin

24
Q

Type IV collagen

A

basement membranes

25
Type V collagen
widespread, particularly found in cornea
26
Collagen
* alpha-ketoglutarate, vit C, oxygen, iron are required for hydroxylation of proline (prolyl hydroxylase) and subsequent cross-linking of proline residues * hydroxylysine also undergoes cross-linking * collagen has proline every 3rd amino acid; also has abundant lysine * scurvy: vit c deficiency
27
Wound
* tensile strength never equal to prewound (80%) * type III collagen: predominant collagen type synthesized for days 1--2 * type I collagen: predominant collagen type synthesized for days 3-4 * Type III replaced by type I by 3 weeks * at 6 weeks, wound is 80% of its final strength and 60% of its original strength * at 8 weeks, wound reaches maximum tensile strength, which is 80% of its original strength * max collagen accumulation at 2-3 weeks after that --> amount of collagen stays the same but continued cross-linking improves strength * d-Penicillamine - inhibits collagen cross linking
28
Essentials for wound healing
* moist environment (avoid desiccation) * oxygen delivery - optimal fluids, no smoking, pain control, arterial reconstruction, supplemental O2 (want transcutaneous oxygen measurement TCOM > 25mmHg) * avoid edema - leg elevation, compression * remove necrotic tissue
29
Impediments to wound healing
* bacteria > 10^5 / cm2 (decrease O2 content, collagen lysis, prolonged inflammation) * devitalized tissue and foreign bodies (retards granulation tissue formation and wound healing) * cytotoxic drugs (5FU, methotrexate, cyclosporine, FK506) * diabetes can contribute to poor wound healing by impeding the early-phase response * albumin < 3 * steroids - prevent wound healing by inhibiting macrophages, PMNs, and collagen synthesis by fibroblasts; decrease wound tensile strength as well (vitamin A counteracts effects of steroids on wound healing) * wound ischemia (fibrosis, pressure, poor arterial inflow, poor venous outflow, smoking, radiation, edema, vasculitis)
30
Osteogenesis imperfecta
type I collagen defect
31
Ehlers-Danlos syndrome
10 types identified; all collagen disorders
32
Marfan's syndrome
fibrillin (collagen) defect
33
Epidermolysis bullosa
excessive fibroblasts; tx: phenytoin
34
Diabetic foot ulcers
charcots joint (2nd MTP joint); 2/2 neuropathy; pressure leads to ischemia
35
Leg uclers
90% of leg ulcers due to venous insufficiency; tx: Unna boot, elastic wrap
36
Scars
contain a lot of proteoglycans, hyaluronic acid and water * scar revisions wait for 1 year to allow maturation; may improve with age * infants heal with little or no scarring
37
Cartilage
contains no blood vesels
38
Denervation
has no effect on wound healing
39
Chemotherapy
has no effect on wound healing after 14 days
40
Keloids
autosomal dominant; dark skinned * collagen goes beyond original scar * tx: XRT, steroids, silicone, pressure garments
41
Hypertrophic scar tissue
dark skinned; flexor surfaces of upper torso * collagen stays within confines of scar * often occurs in burns or wounds that take a long time to heal * tx: steroids, silicone, pressure garments

Wound Healing (1 decks)

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