Regeneration And Repair Flashcards
What 2 processes are involved in repair?
Regeneration: cell proliferation
Connective tissue deposition: laying down fibrous connective tissue when lost tissue can’t be replaced by regeneration alone
What is connective tissue made of?
ECM
Support (stromal) cells — make ECM
Blood vessels, lymph vessels, and nerves
What is the main fiber type found in most connective tissues?
Collagen — fibrous protein
This term refers to the ability of a tissue to repair itself
Intrinsic proliferative capacity
What cell types proliferate during repair?
Surviving functional cells
Vascular endothelial cells
Fibroblasts
What influences a cell’s proliferative capacity?
What part of the cell cycle they spend the most time in
- G0 is resting phase, all other are active phases
What are the 3 main tissue types?
Labile tissue
Stable tissue
Permanent tissue
Which of the 3 tissue types has the highest capacity for regeneration?
Labile tissue
Which of the 3 tissue types has the lowest capacity for regeneration?
Permanent tissue has no capacity for regeneration
The cells of this tissue are capable of entering G1 but are minimally proliferative
Stable tissue
What makes labile tissue have a high regen capacity?
Cells never spend time in G0 and are continuously dividing
High amount of stem cells vs other tissues
Where can labile tissue be found?
GI epithelium
Skin
Oral mucosa
Bone marrow
Why are the cells of stable tissue minimally proliferative?
G0 in normal state but will enter G1 in response to injury
Where can stable tissue be found?
Most solid organs
Kidney
Pancreas
Andrenal glands
Lungs
Liver an exception — high regen capacity
Why are cells of permanent tissue not able to proliferate?
Perpetually in G0
What happens if permanent tissue is dies?
Repair via connective tissue deposition —> decreased function bs scar tissue is nonfunctional
Where can permanent tissue be found?
Neurons, cardiac tissue
What are the 2 major mechanisms in regeneration?
Priming phase: cytokines make remaining cells competent to respond to growth factor signals
Proliferation phase: growth factors act on primed cells to enter cell cycle
What are 3 limitations of regeneration?
Can’t repair everything:
Severe or chronic injury
Injury to connect tissue
Injury to non-dividing cells
No regeneration —> fibrosis/scar formation
When is liver regeneration limited?
Residual tissue not structurally intact
Infection/inflammation —> connective tissue deposition
Destruction of reticulin (liver connective tissue) —> scar formation but remaining cells will have regen capacity
What are the 3 phases involved in repair by connective tissue deposition?
Inflammatory phase
Proliferative phase
Remodeling phase
What happens in the inflammatory phase?
- Damaged tissue removal
- Cytokine and growth factor release
What happens in the proliferative phase?
Angiogenesis
Fibroblast proliferation —> collagen and other ECM deposition
What happens in the remodeling phase?
- Degradation of ECM —> connective tissue remodeling
