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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

A

cartilage

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
Q

Type V collagen

A

widespread, particularly found in cornea

26
Q

Collagen

A
  • 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
Q

Wound

A
  • 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
Q

Essentials for wound healing

A
  • 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
Q

Impediments to wound healing

A
  • 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
Q

Osteogenesis imperfecta

A

type I collagen defect

31
Q

Ehlers-Danlos syndrome

A

10 types identified; all collagen disorders

32
Q

Marfan’s syndrome

A

fibrillin (collagen) defect

33
Q

Epidermolysis bullosa

A

excessive fibroblasts; tx: phenytoin

34
Q

Diabetic foot ulcers

A

charcots joint (2nd MTP joint); 2/2 neuropathy; pressure leads to ischemia

35
Q

Leg uclers

A

90% of leg ulcers due to venous insufficiency; tx: Unna boot, elastic wrap

36
Q

Scars

A

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
Q

Cartilage

A

contains no blood vesels

38
Q

Denervation

A

has no effect on wound healing

39
Q

Chemotherapy

A

has no effect on wound healing after 14 days

40
Q

Keloids

A

autosomal dominant; dark skinned

  • collagen goes beyond original scar
  • tx: XRT, steroids, silicone, pressure garments
41
Q

Hypertrophic scar tissue

A

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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