Tissue Repair Flashcards
How is tissue repair defined?
restoration of tissue architecturally and functionally
Tissue repair can occur via what two mechanisms?
regeneration of the injured tissue
replacement of lost tissue
(part of each two mechanisms play vary from tissue to tissue)
Both mechanism require:
- cell proliferation
- interaction between cells and the presence of intact or altered extracellular matrix
Compare HAV to HBV.
HAV (no chronic HepA)
- hepatic necrosis
- recover or die
- not destroying hepatocyte
HBV (chronic Hep B)
- kills hepatocyte and matrix
Describe cell proliferation.
Continuously proliferating cells can easily regenerate after injury or being used
- contains pools of stems cells close by
- immune + for CD34, CD117, Ki67
What is totipotent cell?
cell can differentiate into any cell type
Where is the first checkpoint?
G1/S - check for DNA damage
-may undergo apoptosis if defect
Where is the second checkpoint?
G2/M
What three groups are tissues of the body divided?
Continuously dividing (labile) - skin basal, GI, hair [short G0] Stable tissues - liver, kidney, lung alveoli, bond, breast, endocrine, adipose [ long G0] permanent - neurons in CNS, ganglia in PNS, cardiac, skeletal muscle [cannot divide]
Where are the three sites of stem cells in the skin?
epidermis
sebaceous gland
hair follicle bulge
Haematopoietic stem cells can differentiate into ?
RBC, WBC (lymphocyte, monocyte, eosinophil, basophil, neutrophil) , platelets
What is the actions of growth factors?
stimulate cell division and proliferation
promote cell differentiation & survival
What is EGF?
epithelial growth fact
mitogenic for skin & fibroblasts
What is TGF?
transforming growth factor
hepatocytes & epithelials
What is PDGF?
platelet derived growth factor
smooth muscle mitogens
cytokines
Cytokines can be present in which instances?
injured tissue remnant
inflammatory cells, macrophages, vascular endothelial cells
cytokines from fibroblasts
Where are cytokines stored?
extracellular matrix
- basement membrane
- interstitial matrix
What purpose does the basement membrane and interstitial matrix serve?
- sequesters water and minerals from circulation
- stores presynthesized growth factors
- give cells a scaffolding upon which to adhere and do their assigned tasks
What is the consequence if the ECM is destroyed?
can’t regenerate tissue
-scar forms instead
What does the ECM regulate?
proliferation, movement, and differentiation of the cells
What are the stages of tissue repair?
regeneration
scarring
Where does regeneration occur frequently?
labile tissues
Where does regeneration occur to a limited extent>
stable tissues
- kidney (if removed the other one undergoes hypertrophy and hyperplasia)
- liver (remove part of liver, some will grow back)
Describe the theoretical aspect of injury.
Blood clots and releases growth factors
- Inflammation
- granulation tissue
- wound contraction
