Fiser.14.WoundHealing Flashcards
What is the rate of epithelialization during the first 10 days of wound healing?
1-2mm/day
what is the name of the phase of wound healing during days 1-10?
inflammation
what are the two cell types seen during the first 10 days of wound healing?
PMNs, macrophages
what is the name of the phase of wound healing from 5 days to 3 weeks?
proliferation
what type of collagen replacement is seen during the proliferation phase (5 days to 3 weeks)?
type III collagen replaced by type I
what type of cell is seen during the proliferation phase of wound healing? (5 days to 3 weeks)?
fibroblasts
name three processes that occur during the proliferation phase of wound healing
collagen deposition, neovascularization, granulation tissue formation
What is the name of the phase of wound healing occurring from 3 weeks to 1 year?
Remodeling
What occurs to collagen during the remodeling phase of wound healing (3 weeks to 1 year)?
collagen cross-linking, net amount of collagen does not change with remodeling but you get significant production and degradation
What happens to vascularity of tissue during the remodeling phase of wound healing (3 weeks to 1 year)?
decreased vascularity
what is the rate of peripheral nerve regeneration with wound healing?
1mm/day
name the order of arrival of cell types to a wound for wound healing? (5 types)
platelets; PMNs; macrophages; lymphocytes; fibroblasts
what cell type is essential for wound healing and why?
macrophages are essential for wound healing due to release of growth factors, cytokines
what are the two roles of fibronectin in wound healing?
chemotactic for macrophages; anchors fibroblasts
what is the function of fibroblasts in wound healing?
replace fibronectin-fibrin with collagen
what is the predominant cell type in a wound on days 0-2?
PMNs
what is the predominant cell type in a wound on days 3-4?
macrophages
what is the predominant cell type in a wound on days >5?
fibroblasts
what are the two components of a platelet plug?
platelets and fibrin
what are the three components of the provisional matrix in wound healing?
platelets, fibrin, and fibronectin
why does reopening a wound result in quicker healing the second time?
healing cells are already there, resulting in accelerated wound healing
what is the most important factor in healing open wounds by secondary intention?
epithelial integrity
what three sites do cells migrate from in healing by secondary intention?
hair follicles (#1 site); wound edges; and sweat glands
Name two problems a/w unepithelialized wounds
leak serum and protein ; promote bacterial growth
what is the factor on which wound healing by secondary intention is dependent upon?
dependent upon development of granulation tissue within the wound
what is the factor on which wound healing by primary intention is dependent upon?
tensile strength
what collagen variables affect wound healing by primary intention? (2)
depends on collagen deposition and cross-linking of collagen
what is the strength layer of the bowel?
submucosa
what is the weakest time point for a small bowel anastomosis?
3-5 days
what is a myofibroblast?
a smooth muscle fibroblast
how do myofibroblasts communicate?
via gap junctions
what are two wound healing processes that myofibroblasts are involved with?
involved in wound contraction and healing by secondary intention
how well does wound contraction occur in the perineum compared to the leg
perineum has better wound contraction than the leg
what is the most common type of collagen?
Collagen Type I
where is type I collagen found? (3 locations)
skin, bone, tendons
what is the primary type of collagen in a healed wound?
Type I Collagen
where is type II collagen found?
cartilage
where is type III collagen found? (3)
increased in a healing wound, blood vessels, skin
where is type IV collagen found?
basement membranes
where is type V collagen found?
widespread, particularly in cornea
name four molecules required for hydroxylation and cross-linking of proline residues
alpha keto glutarate, vitamin C, oxygen, iron
what amino acid allows cross-linking in collagen
cross linking of proline residues
how frequently does proline occur in collagen?
proline occurs every third amino acid
how does collagen’s proline cross-linking affect wound tensile strength?
proline cross-linking improves wound tensile strength
what is the underlying cause of scurvy?
vitamin C deficiency
what is the highest tensile strength of a healed wound compared to pre-wound tensile strength?
up to 80% of pre-wound tensile strength
does a wound’s tensile strength ever reach pre-wound levels?
nopes
what is the predominant type of collagen healed in days 1-2 of wound healing?
Type III collagen
what is the predominant type of collagen healed in days 3-4 of wound healing?
type I collagen
at what time during wound healing is all of the type III collagen replaced by type I collagen
by three weeks post-wound
at what time during wound healing does a wound reach maximum tensile strength?
at 8 weeks at 80% of original wound strength
at what time during wound healing does maximum collagen accumulation occur? what occurs afterwards?
maximum collagen accumulation at 2-3 weeks –> after that the amount of collagen stays the same but continued cross-linking improves strength
what medication inhibits collagen cross-linking?
d-penicillamine
why is moisture essential for wound healing?
prevents dessication
what are 5 ways you can improve oxygen delivery for wound healing?
optimize fluids, no smoking, pain control, arterial revascularization, supplemental oxyten
what is the ideal transcutaneous oxygen measurement for wound healing?
> 25mmHg
how do you avoid leg edema to improve wound healing?
leg elevation
what concentration of bacteria is an impediment to wound healing?
bacteria > 10^5 / cm2
what are three causes of increased bacteria concentration in a wound bed?
reduced oxygen content, collagen lysis, prolonged inflammation
how does devitalized tissue affect wound healing?
retards granulation tissue formation and wound healing
how do foreign bodies affect wound healing?
retards granulation tissue formation and wound healing
how do cytotoxic drugs affect wound healing? give four examples of drugs
5FU, methotrexate, cyclosporine, FK-506 –> can impair wound healing in the first 14 days after injury
how does diabetes affect wound healing?
can contribute to poor wound healing by impeding the early phase inflammation response b/c hyperglycemia causes poor leukocyte chemotaxis
what albumin level is a risk factor for poor wound healing?
albumin < 3.0
how do steroids affect wound healing?
prevent wound healing by inhibiting macrophages, PMNs, and collagen synthesis by fibroblasts; reduces wound tensile strength as well
what is the effect of vitamin A on wound healing for patients on steroids?
vitamin A counteracts the adverse effects of steroids on wound healing
what daily dose of vitamin A is required to counteract the adverse effects of steroids on wound healing?
25,000 IU qd
name 8 causes of wound ischemia
fibrosis, pressure (sacral decub, pressure sore), poor arterial inflow (atherosclerosis), poor venous outflow (venous stasis), smoking, radiation, edema, vasculitis
how does osteogenesis imperfecta affect wound healing?
type I collagen defect
how does Ehler-Danlos syndrome affect wound healing?
10 types have been identified and all are a/w collagen disorders
How does Marfan’s syndrome affect wound healing?
fibrillin defect (connective tissue protein)
how does epidermolysis bullosa affect wound healing?
excessive fibroblasts
how do you treat epidermolysis bullosa?
phenytoin
how does scurvy affect wound healing?
vitamin C deficiency prevents collagen cross-linking
how does pyoderma gangrenosum affect wound healing?
a condition that causes tissue to become necrotic, causing deep ulcers that usually occur on the legs. When they occur, they can lead to chronic wounds. Ulcers usually initially look like small bug bites or papules, and they progress to larger ulcers.
what is the MC location of diabetic foot ulcers?
at Charcot’s joint (2nd MTP joint), then toes
what is the pathophysiology of development of diabetic foot ulcers?
2/2 neuropathy, can’t feel feet, pressure from walking leads to ischemia
what is the underlying cause of 90% of leg ulcers
venous insufficiency
what is the treatment for leg ulcers?
Unna boot (elastic wrap)
name three molecules in high concentration in scars
proteoglycans, hyaluronic acid, water
how long should you wait before performing a scar revision?
wait 1 year to allow maturation, may improve with age
how do infants scar?
they heal with little or no scarring
how is oxygen and nutrients delivered in cartilage and why?
cartilage is avascular, so you get O2 and nutrients by diffusion
what is the effect of denervation on wound healing?
no effect on wound healing
what is the timing of the effect of chemotherapy on wound healing?
has no effect on wound healing after 14 days
how are keloids inherited?
autosomal dominant
what skin pigmentation is at increased risk for keloids?
dark skin
what occurs to collagen formation in a keloid?
collagen goes beyond the original scar
how do you treat keloids (4)
intra-lesion steroid injection, silicone, pressure garments, XRT
what are four risk factors for hypertrophic scar tissue?
dark skinned, flexor surfaces of upper torso, burns, wounds that take a long time to heal
what occurs to collagen formation in hypertrophic scar tissue?
collagen stays within confines of the original scar
how do you treat hypertrophic scar tissue? (3)
steroid injection, silicone, pressure garments
name four contents of alpha granules in platelets
platelet factor 4, beta-thrombomodulin, platelet-derived growth factor (PDGF), transforming growth factor beta (TGF beta)
what is the function of platelet factor 4 in platelet granules?
allows platelet aggregation
what is the function of beta thrombomodulin in platelet granules?
binds thrombin
what is the function of platelet-derived growth factor (PDGF) in platelet granules?
chemoattractant
what is the function of transforming growth factor beta (TGF beta) in platelet granules?
modulates aggregation, thrombin binding, and chemoattractant
what are the three contents of dense granules in platelets?
adenosine, serotonin, calcium
name three platelet aggregation factors
TXA2, thrombin, platelet factor 4