Flashcards in Fiser Chapter 14. WOUND HEALING Deck (37)
Order of wound healing
Inflammation phase (days 1-10)
PMNs, macrophages, EPITHELIALIZATION (1-2 mm/day)
Proliferation phase (5 days to 3 weeks)
Fibroblasts, COLLAGEN DEPOSITION, neovascularization, GRANULATION TISSUE, type 3 collagen replaced with type 1
Remodeling phase (3 weeks to 1 year)
Decreased vascularity, net amount of collagen does not change, although significant production and degradation occur, collagen CROSS LINKING occurs
How fast do peripheral nerves regenerate?
Order of cell arrival to wound?
5. Fibroblasts (proliferation and remodeling)
Predominant cell type in days 0-2?
Predominant cell type in days 3-4?
Predominant cell type in days 5 onward?
True or false, reopening a wound results in quicker healing the 2nd time?
True, as cells are already present there
Most important factor in healing open wounds (secondary intention)
-unepithelialized wounds leak serum and protein, and promote bacteria
Most important factor in healing close wounds (primary intention)
-Depends on collagen deposition and cross-linking of collagen
Strength layer of bowel
Weakest time point for small bowel anastomosis
How do myofibroblasts communicate?
-Involved in wound contraction and healing by secondary intention
Does the perineum or leg has better wound contraction?
I: Most common; skin, bone, tendon; primary collaged in a HEALED WOUND
III: Increased in HEALING wound; vessels; skin
V: Cornea, widespread
Hydroxylation (prolyl hydroxylase) and cross-linking of proline residues in collagen need what?
-d-Penicillamine inhibits collagen cross-linking
Collagen has a lot of what amino acid?
Proline (every 3rd aa): proline cross-linking improves wound tensile strength
Tensile strength of a wound gets how good?
80% pre-wound max
Predominant collagen type in healing wound
1-2 days: type 3
3-4 days: type 1, and replaces type 1 by 3 weeks
When does a wound reach maximum tensile strength?
8 weeks (80%)
When is maximum collagen accumulation in a healing wound reached?
2-3 eweks, after that the amount stays the same, but you have continued cross-liking to improve strength
What is essential for wound healing?
-Oxygen delivery (fluids, no smoking, pain control, revasc, supplemental O2 if needed): want transcutaneous oxygen measurement TCOM > 25 mm Hg
-Avoid edema (leg elevation)
-Remove necrotic tissue
Impediments to wound healing
-Bacteria > 10^5/cm^2
-Devitalized tissue and foreign bodies
-Cytotoxic drugs (5FU, methotrexate, cyclosporine, FK-506, etc can impair wound healing in 1st 14 days after injury)
-DM: impedes early-phase inflammation response, hyperglycemia causes poor leukocyte chemotaxis
- Albumin <3.0
-Steroids: inhibit macrophages, PMNs, and collagen synthesis by fibroblast; also decreases wound tensile strength
-Wound ischemia: fibrosis, pressure, atherosclerosis, venous stasis, smoking, radiation, edema, vasculitis
How does DM impede wound healing?
Hyperglycemia causes poor leukocyte chemotaxis
How do steroids prevent wound healing?
Inhibiting macrophages, PMNs, and collagen synthesis by fibroblasts; decrease wound tensile strength
How can you counteract effect of steroids on wound healing?
Vitamin A 25,000 IU per day
Diseases associated with abnormal wound healing
Osteogenesis imperfect: type 1 collagen defect
Marfan's syndrome: fibrillin defect
Epidermolysis bullosa: excessive fibroblasts, tx phenytoin
Scurvy (vit D def)