Wound Healing Flashcards
Define wound healing.
Restoration of tissue architecture and function after an injury
What is the difference between wound healing and wound repair?
Healing = complete restoration of tissue
Repair = incomplete restoration
What are the steps of wound healing model?
- Damage
- Inflammation
- Removal of dead tissue
- Replacement by 4.scar or tissue
- =healing
What are the three cell types in our body?
- Labile cells
- Permanent cells
- Stable cells
What are examples of labile cells? Can they regenerate?
Cells that have high turnover rate, like epithelium. Chance of regeneration is excellent
What are examples of stable cells? Can they regenerate?
Cells that normally do not undergo proliferation, but remain capable of cell division.
Chance of regeneration is good
What are examples of permanent cells? Can they regenerate?
Neurons
Cardiac muscle
Skeletal muscle
Heals by scarring
What enables a tissue to undergo regeneration?
Presence of stem cells
What determines if a tissue that is able to undergo regeneration undergoes scarring?
The extent of damage
What are the three phases of healing?
- Inflammatory
- Proliferative
- Remodeling (maturation)
What are the two events that occur during inflammation? When does this occur?
Clot formation, chemotaxis
Usually first week
What are the three events that happen in proliferation? When does this occur?
- Re-epithelialization
- Angiogenesis
- Provisional matrix
Second week
What are the two events that occur in the maturation (remodeling) stage
Collagen matrix
Wound contraction
Third week
What is the major molecule that signals angiogenesis? What cell secreted this?
VEGF–macrophages secrete this
What are the two major events that happen in angiogenesis?
Capillary budding
Endothelial cell proliferation
What cell is the “director” of wound healing? Why?
Macrophage, since is secretes cytokines ike VEGF
What is the major chemical in fibrogenesis? What cells secrete this?
TGF-beta–macrophages
What are the two major events that occur in fibrogenesis?
- Fibroblast activation/proliferation
2. Collagen deposition
What are the two enzymes secreted by macrophages that facilitate debridement of tissue/debris?
Collagenase
Elastase
What are the two types of chemicals secreted by macrophages that have an antimicrobial activity?
Nitric acid
ROS
What are the five chemicals secreted by macrophages that promote chemotaxis?
**TGF-beta** IL-1 TNF KGF-7 PDGF
What are the three chemicals secreted by macrophages that stimulate angiogenesis?
VEGF
FGF-2
PDGF
What are the five chemicals secreted by macrophages that signal for deposition and remodeling of the ECM?
TGF-beta PDGF TNF IL-1 MMPs
What is the time frame for secretion of granulation tissue?
3-5 days
What is the difference between granuloma and granulation tissue?
Granulation tissue = tissue surrounding granuloma, that is NOT macrophages
What is histological characteristic of granulation tissue? (3)
Proliferation of fibroblasts
new thin walled capillaries
loose ECM
What does granulation tissue result in?
Fibrosis (scarring)
What is the difference of early vs late stage granulation tissue?
Late = Less vascular, only scattered macrophages, more matrix and fibroblasts
Is granulation tissue permanent?
No, just trying to cover damage until collagen can be deposited
The (BLANK) granulation tissue, the more contraction, and the greater risk of organ impairment.
More
How do scars appear histologically?
Light eosinophilic tissue relative to surrounding tissues
What is the stain that highlights collagen? Color?
Trichrome stain = blue
What is the first (primary) intention of skin healing?
skin is opposed (think sutures)
What predominates in primary intention: epithelial regeneration or fibrosis?
Epithelial regeneration
What is a 2nd intention healing? What does this lead to?
When edges cannot be lined up. This leads to more granulation tissue = more fibrosis
What is the difference between first and second intention healing in terms of wound apposition?
Primary are well apposed, secondary are not
What is the difference between first and second intention healing in terms of necrotic debris, exudate, and fibrin to be removed?
Secondary has large tissue defects/has more necrotic debris
What is the difference between first and second intention healing in terms of granulation tissue
More granulation tissue in secondary
What is the difference between first and second intention healing in terms of myofibroblast wound contraction?
Myofibroblasts may cause contraction in secondary
What is wound contraction? What cell type is responsible for this?
Reduction in the size of a wound that is healed by second intention. Myofibroblasts in the granulation tissue
What type of wounds are contractures seen in particularly?
Serious burns
What are the two places where contractures are particularly problematic?
Around joints
In any opening (stenosis)
What are myofibroblasts, and what is their function?
Hybrid of fibroblasts and smooth muscle
Can secrete collagen, and contract
What is the cause of decubitus ulcers (bed sores)?
Localized Ischemia
What is the nutritional deficiency that can lead to ineffective healing?
Vit C deficiency
What is the most common cause of delayed wound healing?
Infection
What are the three pathologic aspects of repair?
- Keloids
- Exuberant granulation tissue
- Contractures
What is “proud flesh”?
When wounds may generate excessive granulation tissue in healing, preventing wound closure
What are the histological characteristics of a keloid? (what is and is not there compared to normal)
Dermis replaced by an irregularmeshwork of collagen w/o many cells, and lacking glands and hair follicles
What is a hypotrophic scar?
Scar that have a sunken appearance and hyperpigmentation d/t loss of collagen and ground substance
What is a hypertrophic scar?
Similar to keloid, but does not get worse beyond 6 months, and does not recur
What is the clinical difference between hypertrophic scars, and keloid scars?
Keloid grow beyond the scar border, and occurs later
Hyper are raised within the scar margins.
What is proud flesh? Is this conducive to healing?
When granulation tissue grows out too exuberantly, and PROTRUDES from the wound
This is not conducive to healing
What are the two processes involved in regeneration?
Proliferation
Migration
What is the histological difference between keloids and hypertrophic scars? (hint, collagen, and myofibroblasts)
Keloids have a haphazard arrangement of collagen, few myofibroblasts
Hypertrophic scars have numerous myofibroblasts, collagen oriented parallel to skin surface