9 Flashcards
phases of wound healing
- inflammation/debridement2. proliferation/repair3. maturation/remodeling
Inflammation and debridement phase of wound healing
hemostasis (constrict–>dilate, permeability)PMN–>monocytes/macrosphagocytosis, cytokine release, enzyme activation (MMP)1-3 days
proliferation/repair phase of wound healing
fibroblast, endothelial cells, epithelial cellscollagen production (TGFb), capillary ingrowth (VEGF), wound contraction (myofibroblasts–TGFb), wound coverage (TGFa,EGF)granulation tissue4-12 days
type of collagen in wounds
III initially then type I (TGF beta)fibroblasts
what is granulation tissue composed of
capillary bedfibroblastsmacrophagesground substance of collagen, fibronectin, HA
maturation and remodeling phase of wound healing
strengthening of collagen decr III incr Imost important phase
strength of tissue at 1 week vs 3 weeks vs 3 months
1 week 10 %3 weeks 30%3 months 80%
comparison of breaking strength of different tissues across time
bladder > stomach > colon > skin
GI tract has 4 layers EXCEPT in what areas
serosa, muscularis propria, submucosa, mucosaEXCEPT esophagus, rectum
what layer of the GI tract carries the majority of the strength and what proportions of collagen does it contain
SUBMUCOSAtype I 68%type III 20%type V 12%
difference btwn skin and GI epith in terms of collagen production
skin collagen is made by fibroblasts, contains I, IIIGI collagen is made by fibroblasts < sm muscle cells I, III, V
“lag phase” of GI wound healing
strength of anastomoses decreases sign in first 48 hours due to collagen breakdown (colon the most)net loss in strengthcollagenase activity is higher days 0-3 compared to skin (leads to decr strength)
stress applied to GI healing that is not evident in skin healing
sheer stress due to increased intraluminal P, peristalsisalso bacterial flora of aerobic and anaerobicvascular perfusion is more critical to GI vs skin; hypoperfusion/shock more dramatically affect GI healing > skin
T/F retrospective 225 dogs with GI sx, showed intraop hypotension as a risk factor for developing septic peritonitis and death post op
TRUE
at what level of PO2 does mature collagen fail at
PO2 < 40 mm Hg mature collagen will failPO2 < 10 mm Hg halts angiogenesis, epithelialization
critical components of success to GI healing
local factors–preserve blood supply, avoid tensionsystemic factors–maintain perfusion, CO, PO2
why is fascial healing prolonged compared to skin and GI
prolonged in fascia bc inflammatory cells and fibroblasts must migrate a longer distance before reaching the relatively avascular/acellular fascial layertakes 14 weeks to achieve 60% strength
how far should you space fascial sutures
3 mmstudies in rats show sutures placed 1.5 mm vs 3. 0mm3.0mm sutures showed 3x greater wound strength and retained strength at 2 days
how fast does the bladder re-epithelialize
2-4 days
peak collagen synthesis and strength of bladder healing
collagen synthesis in bladder peaks at day 5 and achieves 100% strength within 21 daysmaybe dues to KGH and TGHa
breaking strength of first intention healing of linear wounds dogs vs cats
Bohling et albreaking strength was less in cats and was equivalent to only half of that achieved by dogs
breaking strength of second intention wounds dogs vs cats
granulation tissue was observed faster in dogs (4.5 d) vs cats (6.3d)mean time to cover wound completelydog 7.5 d vs cat 19 d
role of subcutaneous tissues in the wound healing of dogs vs cats
removal of SQ was associated with decrease in the rate of production of granulation tissue and wound contraction (more so in cats than in dogs)
local factors to impede wound healing
- wound perfusion2. tissue viability3. wound fluid accumulation4. wound infection5. mechanical factors
