Wound Healing Flashcards
Three phases of wound healing?
- Inflammatory
- proliferative
- remodeling
How long does the inflammatory phase last?
3 to 5 days
Role of the fibrin clot
Secures hemostasis, matrix for cells to migrate during repair, reservoir of cytokines and growth factors released as activated platelets degranulate
First white blood cells to enter would
Neutrophils arrive at wound site within minutes
Second white blood cells to enter wound
Macrophages, continue micro debridement and release growth factors
How long does proliferative phase last?
Starts as early as day 3 and lasting up to 3 weeks
First collagen to be deposited in a healing wound?
Type III collagen, immature
Synthesized by fibroblasts
What happens during proliferative phase?
Angiogenesis
Formation of immature collagen
Epithelialization
What happens during inflammatory phase?
Formation of fibrin clot
Hemostasis
Release of growth factors
Micro debridement
Strength of healed wound with scar tissue
80% of original strength
How long does remodeling phase last?
Starting at three weeks to several years
What type of collagen forms as remodeling remodeling phase progresses?
Stronger type I collagen
Regeneration rate for peripheral nerves
1 mm per day
Describe the term for what happens to the distal nerve segment after severance
Wallerian degeneration.
Injured axons break up and are phagocytized by Schwann cells and macrophages
Indirect bone healing involves formation of what?
A callus that acts as a splint
Two types of direct bone healing
Gap healing
Contact healing
(No callus formation)
Type of bone deposited in healing contact zones
Lamellar bone
Type of bone deposited in healing gaps
Fibrous tissue, fibrocartilage, and woven bone
How long until radiographic evidence of bone formation is evident after extraction?
4 to 6 months
What has a greater survival rate, full thickness or split thickness skin graft?
Split thickness grafts have greater survival rates clinically. Full thickness grafts are slower to revascularize, but less susceptible to trauma.
Number of organisms required for wound infection
100,000 organisms per gram of tissue
Characteristics of hypertrophic scars
Arise shortly after injury.
Circumscribed within the boundaries of the wound.
Eventually recede.
Characteristics of keloids
Months after injury.
Grow beyond wound boundaries.
Rarely subside.
Treatment of keloids?
Injection of corticosteroids to inhibit protein synthesis
How long does peripheral vasoconstriction from smoking a cigarette last?
Can last up to an hour, a ppd smoker is tissue hypoxia for most parts of the day
Effects of HBO on wounds
Increases the quantity of dissolved oxygen and the driving pressure for oxygen diffusion into the tissue.
Stimulates growth of fibroblasts and vascular endothelial cells, increases tissue vascularization, enhances killing ability of leukocytes, lethal for anaerobic bacteria.
Key amino acid in wound healing
Methionine
Half-life of serum pre-albumin versus albumin
Pre-albumin half-life of 2 days
Albumin half-life of 20 days
Normal serum prealbumin
22.5 mg/dL
<17 mild deficit
<11 severe deficit
Mechanism of rhBMP-2
Induce undifferentiated mesenchymal cells to differentiate into osteoblasts (osteoinduction)
