18 Questions
What is the primary factor that determines the capacity of a tissue for regeneration?
Degree of damage to the stromal framework
Which type of cells cannot heal by regeneration?
Terminally differentiated cells
What is the primary mechanism of repair in wounds that extend through the basement membrane?
Granulation tissue formation
During which phase of granulation tissue formation do dead cells liberate their autolytic enzymes?
Phase of demolition
What is the result of a wound that only affects the lining epithelium?
Healing by regeneration
What is the process by which lost tissue is eventually replaced by a scar?
Repair
What is the primary function of fibronectin in the wound healing process?
To act as a chemotactic factor for the recruitment of fibroblasts and macrophages
When does the synthesis of collagen by fibroblasts begin after injury?
Within 24 hours
What type of collagen is predominantly produced by day 5 after injury?
Type III
What is the timeframe for vascular proliferation after injury?
48-72 hours
What primarily determines whether healing occurs by regeneration or scarring?
All of the above
What is the primary constituent of mature scar tissue?
Type I collagen
What is the result of minimal destruction of stable cells and intact framework?
Restitution of normal structure
What occurs in conjunction with fibroblast proliferation during wound healing?
Angiogenesis
What is the outcome of necrosis of cells and destruction of framework?
Scarring
What is the relationship between regeneration, repair, and contraction in wound healing?
They are interconnected processes that often occur together
What is the term for the process by which tissue returns to its normal structure?
Restitution of normal structure
What is the term for the process by which new tissue is formed to replace damaged tissue?
Regeneration
Study Notes
Tissue Regeneration
- Tissue regeneration depends on its proliferative ability, degree of damage to stromal framework, and type and severity of damage.
- Labile and stable cells can regenerate if stromal framework is intact.
- Tissues containing terminally differentiated cells (e.g., neurons, skeletal muscle cells) cannot regenerate.
Tissue Repair (Healing by Connective Tissue)
- Repair is the orderly process by which lost tissue is replaced by a scar.
- Wounds extending through the basement membrane to connective tissue lead to granulation tissue formation and eventual scarring.
- Granulation tissue formation occurs in three phases: inflammation, demolition, and ingrowth of granulation tissue.
Phases of Granulation Tissue Formation
- Inflammation phase: characterized by inflammatory exudate, polymorphs, platelet aggregation, and fibrin deposition.
- Demolition phase: dead cells release autolytic enzymes, macrophage infiltration, and proteolytic enzymes from disintegrating polymorphs.
- Ingrowth phase: proliferation of fibroblasts, new blood vessel ingrowth, variable number of inflammatory cells, and fibroblasts actively synthesize and secrete extracellular matrix components.
Extracellular Matrix Components
- Fibronectin and proteoglycans form the 'scaffolding' for rebuilding of the matrix.
- Fibronectin binds to fibrin, acts as a chemotactic factor for fibroblasts and macrophages, and recruits more fibroblasts and macrophages.
- Collagen synthesis begins within 24 hours of injury, with collagen type III being predominant initially, and type I eventually becoming the major collagen of mature scar tissue.
Angiogenesis
- Vascular proliferation starts 48-72 hours after injury and lasts for several days.
- Coincident with fibroblast proliferation, there is an increase in extracellular constituents, mostly collagen, with a decrease in the number of active fibroblasts and new vessels.
Wound Healing
- Healing occurs by regeneration or scarring, depending on the degree of tissue destruction, parenchymal cell proliferation, and stromal framework destruction.
- Regeneration, repair, and contraction are not mutually exclusive processes, and often participate together in wound healing.
Test your understanding of tissue regeneration and repair, including the processes of cell proliferation and migration, and the factors that affect a tissue's ability to regenerate. Learn about the differences between regeneration and repair, and how they contribute to the healing process.
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