Wound Healing Flashcards by tcarlso 3

Define wound healing.

Restoration of tissue architecture and function after an injury

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What is the difference between wound healing and wound repair?

Healing = complete restoration of tissue

Repair = incomplete restoration

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What are the steps of wound healing model?

Damage
Inflammation
Removal of dead tissue
Replacement by 4.scar or tissue
=healing

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What are the three cell types in our body?

Labile cells
Permanent cells
Stable cells

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What are examples of labile cells? Can they regenerate?

Cells that have high turnover rate, like epithelium. Chance of regeneration is excellent

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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

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What are examples of permanent cells? Can they regenerate?

Neurons
Cardiac muscle
Skeletal muscle

Heals by scarring

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What enables a tissue to undergo regeneration?

Presence of stem cells

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What determines if a tissue that is able to undergo regeneration undergoes scarring?

The extent of damage

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What are the three phases of healing?

Inflammatory
Proliferative
Remodeling (maturation)

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What are the two events that occur during inflammation? When does this occur?

Clot formation, chemotaxis

Usually first week

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What are the three events that happen in proliferation? When does this occur?

Re-epithelialization
Angiogenesis
Provisional matrix

Second week

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What are the two events that occur in the maturation (remodeling) stage

Collagen matrix
Wound contraction

Third week

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What is the major molecule that signals angiogenesis? What cell secreted this?

VEGF–macrophages secrete this

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What are the two major events that happen in angiogenesis?

Capillary budding

Endothelial cell proliferation

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What cell is the “director” of wound healing? Why?

Macrophage, since is secretes cytokines ike VEGF

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What is the major chemical in fibrogenesis? What cells secrete this?

TGF-beta–macrophages

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What are the two major events that occur in fibrogenesis?

Fibroblast activation/proliferation

2. Collagen deposition

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What are the two enzymes secreted by macrophages that facilitate debridement of tissue/debris?

Collagenase

Elastase

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What are the two types of chemicals secreted by macrophages that have an antimicrobial activity?

Nitric acid

ROS

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What are the five chemicals secreted by macrophages that promote chemotaxis?

**TGF-beta**
IL-1
TNF
KGF-7
PDGF

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What are the three chemicals secreted by macrophages that stimulate angiogenesis?

VEGF
FGF-2
PDGF

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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.

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?

1. Keloids 2. Exuberant granulation tissue 3. 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 **irregular**meshwork 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