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31 Cards in this Set

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What are the two processes that can occur during healing and repair?
Regeneration of indigenous cells

Replacement of cells by connective tissue (leads to fibrosis)
What are the three classes of cells in terms of regenerative state?
Continuously dividing

Quiescent

Non-dividing
What is quiescence?
Not dividing but have the capacity to divide
What is needed for regeneration to occur?
Stimulating mediators

Intact basement membrane (stroma)
What happens if injury or inflammation destroys the stroma of a tissue?
Fibrosis
Why are the vessels in granulation tissue leaky?
New endothelial junctions are not as tight as mature vessels
What provides the scaffold for fibroblasts in granulation tissue?
Leaky vessels allowing fibrinogen to cleave to fibrin (forming the scaffold)
What mediators stimulate fibroblasts and what happens as a result of this stimulation?
Inflammatory mediators:
- TNF
- FGF
- PDGF

Fibroblasts divide and lay down collagen matrix
What is contact inhibition?
The cessation of of cell growth when cells contact one another
What is fibrosis?
Excess of hard, fibrous tissue with a high collagen content
What is sclerosis?
Hardening fibrotic lesions
When does fibrosis occur?
At the end point of healing when regeneration has failed
What stimulates fibrosis?
Injury

Chronic inflammation

Irritant particles (silica, asbestos)
How do particulates stimulate fibrosis?
Stimulate mediator release from macrophages for direct stimulation of fibrosis
How do scars form from fibrotic tissues?
Matrix remodels

Blood vessels decrease

Myofibroblasts contract

Increased collagen and crosslinking
Why is fibrosis useful?
Walls off infected areas such as abscesses or granulomas

Restores continuity of damaged tissues
What are some cons of fibrosis?
Impaired organ function

Anatomical constrictions

Impedes regeneration
What is healing by first intention?
Clean incisional wounds

Gap easily bridged with a small fibrous scar
What is healing by second intention?
Healing of wounds that are large and/or infected

Resultant scar is larger

If infected, slower healing
What are the factors that can influence healing?
Systemic:
- Nutrition
- Metabolic disorders
- Poor blood supply
- Hormones

Local:
- Infection
- Foreign bodies
- Mechanical stress and movement
- Size and location
What is dehiscence?
Opening of a wound
What are keloids?
Excessive scar formation
What are the symptoms of the "flu?"
Systemic effects of inflammation:
- Fever
- Malaise
- Anorexia
How does inflammation cause fever?
Microbes stimulate TLRs causing them to secrete cytokines

Cytokines act on the hypothalamus causing prostaglandin release

Prostaglandins responsible for fever, malaise, and anorexia
How do tylenol and aspirin alleviate flu-like symptoms?
Inhibit the production of prostaglandins
Why does the flu produce muscle aches?
Muscles make prostaglandins in response to cytokines
Why is fever developed in response to infection?
Increased temperature hinders replication of microbes

Improves ability of leukocytes to kill microbes
What is leukocytosis?
Elevated WBC count
What is a "left shift" in WBC counts and what does this indicate?
High number of less mature neutrophils

Indicative of infection
How does inflammation affect the lever?
Cytokines stimulate the liver to produce complement, opsonizing molecules, and other proteins
What is the acute phase response to infection?
Metabolic systemic effects of inflammation as seen in liver secretions