Chapter 14 - Wound Healing Flashcards
This is the first stage of Wound Healing. Days? Cells?
Inflammation
- Days 1-10
- Hemostasis - immediate, platelets
- Inflammation - PMNs, Macrophages
- Epithelialization - finishes ~2 days, 1-2mm/day
This is the second stage of wound healing. Days? cells?
Proliferation/Fibroplasia
- 5 days-3 weeks
- Fibroblasts - neovascularization; production of collagen and granulation tissue
This is the third stage of wound healing. Days? What happens?
Remodeling/Maturation
- 3 weeks to 1 year
- Type III collagen replaced with type I
- Collagen cross-linking occurs
- Remodeling
- Contraction
- Repigmentation
At what pace do peripheral nerves regenerate?
1mm/day
The order of cell arrival in a wound:
- Platelets
- PMNs
- Macrophages
- Fibroblasts
- Lymphocytes
What do macrophages do in wound healing?
essential for wound healing - release growth factors, cytokines, etc.
What do fibroblasts do in wound healing?
replace fibronectin-fibrin with collagen
What does fibronectin do in wound healing?
Chemotactic for macrophages
Anchors fibroblasts
Part of the provisional matrix
Besides hemostasis, what do thrombin and fibrin do in wound healing?
act as growth factors for endothelial cells and fibroblasts.
These are the primary cells in days 0-2
PMN’s
These are the primary cells in days 3-4
Macrophages
These are the primary cells in days 5 and on
Fibroblasts
What makes up the platelet plug?
Platelets and Fibrin
What makes up the provisional matrix (scaffold)?
platelets, fibrin, fibronectin
What is meant by accelerated wound healing, and when does it occur?
Reopening of a wound results in quicker healing the 2nd time, as cells are already present
Platelet Alpha granules contain what?
- Platelet Factor 4 - aggregation
- Beta Thrombomodulin - binds thrombin
- PDGF - chemoattractant
Dense granules of platelets contain what?
- Adenosine
- Serotonin
- Calcium
Platelet Aggregation factors include what?
- TXA2
- Thrombin
- Platelet factor 4
Where is platelet-activating factor released from?
Platelets
Where is transforming growth factor-alpha released from?
platelets
Where is fibroblast growth factor released from?
Platelets
Where is Beta Lysin released from and what does it do?
Platelets; antimicrobial
Where are PGE2 and PGI2 released from, and what do they do?
Platelets; Vasodilator
Where is PGF2 released from? What does it do?
Platelets; Vasoconstriction
Unepithelialized wounds leak what and promote what?
Leak serum and protein, promote bacteria colonization
The most important factor in healing closed incisions (primary intention) is what?
Tensile strength
In closed wounds, tensile strength depends on what?
collagen deposition and cross-linking of collagen (occurs in the remodeling/maturation stage)
What is the strength layer of the bowel?
Submucosa
When is the weakest time point for small bowel anastomosis?
Days 3-5
Which has better wound healing - perineum or leg?
perineum
Type I collagen: is it more or less common?
Where is it found in the human body?
What is its role in wound healing?
Most common type
Found in skin, bone, tendons
Primary collagen in the healed wound (replaces type III)
Where is Type II Collagen found?
Cartilage
Where is Type III Collagen found?
Healing wound, also in blood vessels and skin
Where is Type IV collagen found?
Basement Membranes
Type V collagen?
Widespread, particularly in the cornea
These 4 substances are required for the hydroxylation of proline and crosslinking of proline residues.
- Alpha-ketoglutarate
- Vitamin C
- Oxygen
- Iron
Collegen has ________ every 3rd amino acid and abundant _________.
Proline; Lysine
The final tensile strength of a wound is only ever what percentage of the pre-wound strength?
80%
The predominant collagen produced for days 1-2 in wound healing is?
Type III
Predominant collagen synthesized by days 3-4
Type I
At 6 weeks a wound is ____% of final strength and ____% of original
80; 60
At what point does a wound reach its maximal tensile strength?
8 weeks
When does a wound have maximum collagen accumulation?
2-3 weeks. After that, amount stays same but cross-linking improves strength.
What does d-Penacillamine do to collagen?
Inhibits cross-linking
What do you want transcutaneous oxygen measurement to be in a healing wound?
25 mmHg
What is essential to wound healing?
- moist environment
- O2 delivery
- no edema
- debridement of necrotic tissue
What level of bacteria inhibits wound healing and why?
- >10^5
- decreases O2 content
- collagen lysis
- prolonged inflammation
What is the effect of devitalized tissue and foreign bodies on wound healing?
slows/inhibits granulation tissue formation
How does diabetes contribute to poor wound healing?
impedes early phase response
What level of albumin can be a factor in poor wound healing?
<3.0
How do steroids inhibit wound healing?
- inhibit macs, PMNs, collagen synth by fibroblasts
- decreases tensile strength
What can be given to counteract steroid effect on wound healing?
Vitamin A
Osteogenesis Imperfecta is a defect in what?
Type I collagen
Ehlers-Danlos syndrome is what?
Collagen disorder; 10 types identified
Marfan’s syndrome is a defect in what?
Fibrillin (Collagen)
What is Epidermolysis Bullosa, and how is it treated?
Excessive fibroblasts; phenytoin
What is Charcot’s joint?
- 2nd MTP
- diabetic foot ulcer 2/2 to neuropathy
How long do you wait before doing a scar revision?
1 year
Does cartilage contain blood vessels?
No
Does Denervation have an effect on wound healing?
No
Chemo can be given how many days after surgery and have no effect on wound healing?
14
What inheritance is Keloid formation?
Autosomal Dominant
In Keloids, how far does collagen extend, and what is Tx? These are benign fibrous growths caused by overproduction of extracellular matrix and dermal fibroblasts.
Beyond the original scar.
Intralesional steroids are first line (70% response, some require repeat injections). The earlier the better.
Surgery may be necessary if steroids fail.
Other options include XRT, silicone, pressure garments.
Where are hypertrophic scars usually found?
flexor surfaces of upper torso
In hypertrophic scars, how far does collagen extend? How is it managed?
Stays within confines of scar
Treat with steroids, silicone, pressure garments
