TISSUE REPAIR Flashcards
Identify this pathologic repair process
accumulation of excessive amounts of collagen
remain within the confines of the original wound.
May regress spontaneously
Bundles of collagen fibers lie in a parallel arrangement
Hypertrophic scar
Identify this pathologic repair process
scar tissue grows beyond the boundaries of the original wound
Does not regress
Bundles of collagen fibers lie in a disorganized fashion
Frequently recurs after excision
Keloid
List 2 examples of stable tissues
parenchyma of liver, kidney, and pancreas
endothelial cells, fibroblasts, and smooth muscle cells
Which type of tissues/cells best fits the description given below?
can readily regenerate after injury as long as the pool of stem cells is preserved
Labile (continuously dividing) tissues
Special stain to demonstrate collagen
Masson’s Trichrome stain
See attached image. What is the underlying basis?
Exaggerated wound contraction
2 major mechanisms of liver regeneration
- Proliferation of residual hepatocytes
- Repopulation from progenitor cells
Name the localized tumor resulting from proliferation of fibroblasts, with very low metastatic potential
Desmoids (aggressive fibromatoses)
List 1 word that best fits the description given below:
Fibrosis that develops in a tissue space occupied by an inflammatory exudate
Organization
Which type of tissues/cells best fits the description given below?
Inability to proliferate in response to injury; terminally differentiated
Permanent tissues
Which type of tissues/cells best fits the description given below?
minimal proliferative activity in their normal state but capable of dividing in response to injury or loss of tissue mass
Stable tissues
List 3 examples of permanent tissues
- Neurons
- Cardiac myocytes
- Skeletal muscle cells
See the attached image and identify the abnormal pathologic repair process
Exuberant granulation (proud flesh)
Two mechanisms via which repair occurs
- Regeneration
- Scar (connective tissue deposition) formation
List 3 examples of labile tissues
Bone marrow
Skin
GI tract
3 key differences between hypertrophic scars and keloids
Identify the pathologic repair process shown in the attached image
Etiologic basis ?
Wound dehiscence
Secondary to mechanical stress - Vomiting, coughing, or ileus
Most important mediator of fibrosis
TGF-beta
List 6 key differences between healing by first and second intention
See attached table
By when does wound strength reaches approximately 70% to 80% of normal?
Month 3
By when does the wound acquire tensile strength approximately 10% of that of unwounded skin?
End of week 1
Identify the timeline during which the following events are likely to occur in wound healing
increasing collagen deposition, regression of vessels, edema and leukocytic infiltrate
Week 2
Identify the timeline during which the following event is likely to occur in wound healing
granulation tissue formation is at its peak
Day 5
List 1 example of healing by first intention
healing of a clean, uninfected surgical incision approximated by surgical sutures
List examples of healing by second intention
large wounds, abscesses, ulceration, and ischemic necrosis (infarction) in parenchymal organs
How does zinc deficiency impair wound healing?
Zinc: ↑type III collagen; ↓tensile strength
How does copper deficiency impair wound healing?
↓Copper: ↓cross-linking of collagen
How does Vitamin C deficiency impair wound healing?
structurally weakened collagen due to lack of Vit C for hydroxylation of proline and lysyl residues and no cross linking
How does corticosteroid administration affect wound healing?
Glucocorticoids –> inhibition of TGF-β production —->decreased fibrosis and collagen production —->weak scar
- Identify this key event of the wound healing process
- When does it begin?
- When does it reach its peak?
- Granulation tissue
- Day 3
- Day 5
Microscopic appearance of granulation tissue
proliferation of fibroblasts and new thin-walled, delicate capillaries (angiogenesis), in a loose extracellular matrix, with admixed inflammatory cells, mainly macrophages
List 3 actions of TGF-beta in scar formation
- stimulates fibroblast migration and proliferation
- increased synthesis of collagen and fibronectin
- decreased degradation of ECM due to inhibition of metalloproteinases
Which pathway ensures proper patterning of the newly formed vessels in angiogenesis?
Notch pathway
List 4 mediators of angiogenesis
VEGF
FGF
PDGF
TGF-beta
Role of VEGF in angiogenesis
- promotes vasodilation by stimulating the production of NO
- stimulates survival, migration and proliferation of endothelial cells
First step in the tissue repair process
Formation of a fibrin clot
What is the basis for the formation of contractures?
Excessive MMP activation - encourages migration of myofibroblasts at wound edges and scar tissue remodelling
