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Unit 5
healing
34
Pathology
Undergraduate 3
12/09/2014

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Term
True or False

True resolution cannot occur with chronic inflammation
Definition
true
Term
What determines the extend of regeneration? (3)
Definition
ability of cells to divide
number of surviving cells
whether there is a surviving tissue framework to allow normal tissue structure
Term
Skin & mucosal epithelial cells and hematopoetic cells of bone marrow are examples of...
Definition
labile cells
Term
What are the characteristics of labile cells?
Definition
-short life
-rapid rate of division
-divide actively throughout life
-regneration of this tissue is rapid
Term
What are the characteristics of stable cells?
Definition
-reversible postmitotic (remain in interphase for years, can divide if necessary)
-require some connective tissue framework to support regeneration of this tissue
Term
What types of cells make up the liver, kidney, pancreas, endothelium etc?
Definition
stable cells
Term
How does healing of tissue composed of permanent cells occur?
Definition
scarring of tissue
Term
What regulates the net rate of cell proliferation?
Definition
CYCLINS motivate replication!

1. ability to replicate
2. balance between proliferative & inhibitory activity (cyclins)
3. balance between rate of proliferation & cell loss
Term
What modifies cyclin activity?
Definition
growth factors & hormones upregulate
inhibitory signals can impair proliferation/induce apoptosis
Term
What is scarring?
Definition
replacing normal tissue with dense collagenous connective tissue after injury
Term
What causes scarring?
Definition
-regeneration is not possible (cell type, not enough cells, framework destroyed)
-acute inflam is unresolved or there is ongoing tissue necrosis
Term
Damage to the intestinal epithelium due to a rotavirus causing villus atrophy is likely to heal by....
Definition
regeneration
Term
Damage to renal tubule epithelial cells is likely to heal by....
Definition
regeneration if damage is mild
scarring if more extensive
Term
True or False

Liver cells are more likely to successfully regenerate than kidney cells
Definition
true
Term
What are the steps of developing scarring? (6)
Definition
1. Debridement
2. Granular tissue formation
3. Angiogenesis
4. Collagenization
5. Maturation
6. Contraction
Term
What is the role of neutrophils in scar formation?
Definition
release enzymes to liquify debris (involved in debridement)
Term
Why is the formation of granulation tissue important?
Definition
fills the injured area until more mature tissue can develop
highly vascular
Term
Angiogenesis is important in both....
Definition
wound healing & developing collateral vessels in instances of ischemia
Term
What synthesizes collagen?
Definition
fibroblasts
Term
Why is collagenization important?
Definition
gives tensile strength to scar tissue
Term
What is maturation?
Definition
replacing granulation tissue with mature connective tissue
-more collagen, less capillaries & inflam cells
Term
True or False

A fully mature scar is primarily composed of collagen
Definition
true
Term
What is fibronectin?
Definition
a protein which is chemotactic for fibroblasts, helps to 'organize' endothelial cells

-important in granulation tissue formation
Term
What causes contraction of a scar?
Definition
Early on: actomyosin in some fibroblasts
Later: increased [collagen]
Term
Do lacerations affect the dermis or epidermis?
Definition
both
Term
Do burns affect the dermis or epidermis?
Definition
epidermis
Term
What differentiates scar formation from healing of skin wounds?
Definition
skin wounds also requires epithelializtion
Term
What is required for healing by first intention?
Definition
wound edges must be brought close together
Term
What are the steps of healing by first intention?
Definition
1. Hemorrhage & release of thromboplastin (for clotting & scab formation)
2. Loss of contact inhibition causes basal cells to migrate under scab to cut margins
3. Debridement
4. Angiogenesis
5. Collagenization
6. Maturation
6. Contraction & remodeling
Term
When would healing by 2nd intention occur?
Definition
when tissue damage is more extensive
Term
How is healing by second intention different than first? (3)
Definition
-more granulation tissue
-granulation tissue is not covered by epidermis as quickly
-takes longer
-intense inflammation (more necrotic debris)
-wound contraction takes up to 6 wks
Term
What are some complications of healing by second intention?
Definition
-increased risk of secondary inflammatory-mediated injury
-more granulation tissue = more scar tissue mass
-keloid formation (hypertrophic scarring)
-great wound contraction = compromised vascularity/function of the tissue

problem if 2nd intention in brain/heart!
Term
What are keloids?
Definition
abnormal masses of collagen
Term
What factors affect effectiveness of wound healing? (7)
Definition
nutrition
age
drugs
foreign material
blood supply
size/shape/location of wound
presence of infection
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