Flashcards in 14 Wound Healing Deck (98):
what are the phases of wound healing?
inflammation, proliferation, remodeling
how long dose inflammation last?
what happens during inflammation?
pmns, macrophages, epithelialization
how fast does epithelialization work?
how long does proliferation last?
what happens during proliferation?
fibroblasts, collagen deposition, neovascularization, granulation tissue formation, type III collagen replaced w type I
how long does remodeling last?
3w to 1 yr
what happens to vascularity during remodeling?
what happens during remodeling?
collagen cross-linking occurs
does the amount of collagen increase or stay the same during remodeling?
net amount doesn't change but significant production and degradation occur
how fast do peripheral nerves regenerate?
what is the order of cell arrival in a wound?
platelets, PMNs, macrophages, lymphocytes, fibroblasts
illustrate timeline of phases of wound healing with dominant cell types and major physiologic events
what do macrophages do?
essential for wound healing: release growth factors, cytokines, etc.
what does fibronectin do?
chemotactic for macrophages; anchors fibroblasts
what do fibroblasts do?
replace fibronectin-fibrin with collagen
list the prominent cell type by day.
day 0-2: PMNs
days 3-4: macrophages
days 5 and on: fibroblasts
what is a platelet plug consisted of?
platelets and fibrin
what does a provisional matrix consist of?
platelets, fibrin, fibronectin
what is accelerated wound healing?
reopening a wound results in quicker healing the 2nd time (as healing cells are already present there)
what is the most important factor in healing open wounds (secondary intention)
what happens to epithelial cells on the skin near open wounds?
epithelial cells migrate from hair follicles (#1 site), wound edges, and sweat glands
what is epithelial integrity dependent on?
granulation tissue in wound
what happens to unepithelialized wounds?
leak serum, protein, promote bacteria
what is the most important factor in healing closed incisions (primary intention)?
what does tensile strength depend on?
collagen deposition and cross-linking of collagen
what is the strength layer of bowel?
when is the weakest time point for small bowel anastomosis?
how do myofibroblasts communicate?
what are myofibroblasts called in the smooth muscle cell?
what do myofibroblasts do?
involved in wound contraction and healing by secondary intention
what has better wound contraction: perineum or leg?
what is the most common type of collagen?
what is the primary collagen in a healed wound?
what type of tissue is type I collagen?
skin, bone, tendons
what type of tissue is type II collagen
what collagen type is increased in a healing wound?
what type of collagen is in blood vessels and skin?
what type of collagen makes up basement membranes?
what type of collagen is widespread?
what type of collagen is particularly found in the cornea?
what is what is required for hydroxylation?
alpha-ketoglutarate, vitamin C, oxygen, and iron.
what is the enzyme that mediates hydroxylation?
why is hydroxylation needed in wound healing?
cross-links proline residues in collagen
which amino acid crosslinks in collagen? how often is it in the protein?
proline. every 3rd amino acid.
what does proline cross linking do?
improves wound tensile strength
what is scruvy?
vitamin C deficiency
can tensile strength equal to pre-wound?
no. only 80%
which types of collagen are predominant at which periods of wound healing?
days 1-2: type III
days 3-4: type I collagen
when is type III replaced by type I collagen?
by 3 weeks of wound healing
when does a wound reach max tensile strength?
when is maximum collagen accumulation reached? what happens after that?
2-3 weeks. afterwards, continued cross-linking improves strength
what does d-penicillamine do?
inhibits collagen cross-linking
what are the essentials for wound healing?
moist environment, oxygen delivery, avoid edema, remove necrotic tissue
how is oxygen delivery to wound maximized?
optimize fluids, no smoking, pain control, arterial revascularization, supplemental O2
what should transcutaneous oxygen measurement be to maximize wound healing?
TCOM > 25mmhg
what are impediments to wound healing?
bacteria, devitalized tissue, foreign bodies, cytotoxic drugs, diabetes, low albumin, steroids, wound ischemia
how is bacteria an impediment to wound healing?
decreases oxygen content, collagen lysis, prolonged inflammation
how are devitalized tissue and foreign bodies impediments to wound healing?
retards granulation tissue formation
which cytotoxic drugs are impediments to wound healing and when do they impair wound healing?
5FU, methotrexate, cyclosporine, FK-506, etc. impair wound healing in 1st 14 days after injury
how does diabetes contribute to poor wound healing?
impedes early phase inflammation response (hyperglycemia causes poor leukocyte chemotaxis)
how low does albumin need to go before it becomes a risk factor for poor wound healing?
how much bacteria is required before it impedes wound healing?
how do steroids impede wound healing?
inhibit macrophages, PMNs, collagen synthesis by fibroblasts. decreases wound tensile strength as well
what counteracts effects of steroids on wound healing?
vitamin A 25,000 IU qd
what causes wound ischemia?
hypoxia. caused by fibrosis, pressure (sacral decub, pressure sores), poor arterial inflow (atherosclerosis), poor venous outflow (venous stasis), smoking, radiation, edema, vasculitis
what diseases are associated with poor wound healing?
how is osteogenesis imperfecta associated with abnormal wound healing?
type I collagen defect.
how is ehlers-danlos syndrome associated with abnormal wound healing?
10 types identified, all collagen disorders
how is marfan's syndrome associated with abnormal wound healing?
fibrillin defect (connective tissue protein)
how is epidermolysis bullosa associated with abnormal wound healing?
what is the treatment for epidermolysis bullosa?
how where do diabetic foot ulcers occur?
usually at charcot's joint secondary to neuropathy, also toes
what is charcot's joint?
2nd MTP join
what causes leg ulcers?
90% due to venous insufficiency
what is the treatment for leg ulcers?
unna boot (elastic wrap)
what do scars contain?
lots of proteoglycans, hyaluronic acid, water
when do you do scar revisions?
wait for one year to allow maturation; may improve with age
do infants scar?
heal with little or no scarring
does cartilage contain blood vessels? how do they get nutrients and O2?
no. get nutrients and o2 by diffusion
does denervation have any effect on wound healing?
does chemo have any effect on wound healing?
not after 14 days
who gets keloids?
it's autosomal dominant; dark skinned people
what are keloids?
collagen goes beyond original scar
what is treatment for keloid?
intra-lesion steroid injection; silicone, pressure garments, XRT
who gets hypertrophic scar tissue?
where does hypertrophic scar tissue form?
flexor surfaces of upper torso
how is hypertrophic scar tissue different from keloid?
in hypertrophic scar tissue, collagen stays within confines of original scar
how do people get hypertrophic scar tissue?
often occurs in burns or wounds that take a long time to heal
what is the treatment for hypertrophic scar tissue?
steroid injection, silicone, pressure garments
what are the different platelet granules?
alpha and dense granules
what are the alpha granules?
platelet factor 4, beta-thrombomodulin, PDGF, TGF-beta
what does platelet factor 4 do?
what does beta-thrombomodulin do?
what does PDGF do?
what does TGF-beta do?
transforming growth factor beta modulates activity of platelet factor 4, beta-thrombomodulin, and PDGF
what do dense granules contain?
adenosine, serotonin, calcium