MoD 4 (Healing & Repair) Flashcards
Define regeneration:
The growth of cells and tissues to replace lost structures. This requires an intact tissue scaffold (cannot occur if extensive damage).
Define ‘labile’ tissue:
Tissue with continuously dividing cells
Define ‘stable’ tissue:
Tissue with quiescent cells
What is a quiescent cell?
A cell that has reversibly left the cell cycle (G0), as it is not dividing or preparing to divide.
Where can labile cells be found?
Surface epithelia:
- Lining mucosa of secretory ducts of glands
- Epithelia of GI, uterus and urinary tract
Haemopoetic tissue (red bone marrow)
Where can stable cells be found?
Mesenchymal cells (ie fibroblasts, smooth muscle cells) Parenchymal (functional) cells of Liver, Kidney and Pancreas
Define ‘permanent’ tissue:
Tissue containing non-dividing, terminally differentiated cells
Where can permanent cells be found?
- Neurones
- Skeletal muscle cells
- Cardiac muscle cells
What type of cell undergoes asymmetric replication?
Stem cells
What is meant by asymmetric replication?
When a stem cell replicates producing 1 stem cell and 1 stable/permanent cell.
Define fibrous repair:
The replacement of functional tissue with scar tissue
Fibrous repair occurs in response to what 3 triggers?
1 - Chronic inflammation
2 - Damage to collagen framework of a tissue
3 - Necrosis of specialised cells which cannot be replaced
What cell types are required for fibrous repair?
Fibroblasts/Myofibroblasts Endothelial cells Inflammatory cells - Neutrophils - Macrophages - Lymphocytes
What is the role of endothelial cells in fibrous repair?
Angiogenesis
What is the role of fibroblasts in fibrous repair?
Synthesis of extracellular matrix proteins
What is the roles of macrophages/neutrophils in fibrous repair?
Phagocytosis of debris
Which growth factor stimulates angiogenesis?
VEGF
Describe the key steps in angiogenesis:
- VEGF binds to endothelial cell = ACTIVATES
- Activated endothelial cell causes vasodilation and proteolysis of basement membrane
- Endothelial cells proliferate and migrate, then mature and undergo remodelling
- Periendothelial cells are recruited
What is Scurvy caused by?
Vitamin C deficiency
What is Scurvy?
Weak collagen formation due to vitamin C deficiency, causing bleeding gums and prolonged healing.
What are the symptoms of Scurvy?
Bleeding/swollen gums Prolonged healing Fatigue Myalgia Shortness of breath
Why does a vitamin C deficiency cause weak collagen (Scurvy)?
Vitamin C is required for Prolyl hydroxylase and Lysyl hydroxylase, which hydroxylate amino acid residues during collagen synthesis, allowing many cross-linkages to occur, increasing the strength of Collagen
What is Ehlers-Danlos syndrome?
Inherited disease which causes the defective conversion of Procollagen to Tropocollagen (Collagen types I-III have reduced tensile strength), this causing hypermobility of joints and hyperextensible fragile skin
What are the symptoms of Ehlers-Danlos syndrome?
- Hypermobility of joints
- Hperextensible fragile skin
- Poor wound healing
What is Alport syndrome?
Inherited disease affecting type IV collagen primarily in kidneys, cochlea and lens of eye.
Causes kidney failure, cataracts, progressive hearing loss, oedema
What is the name of the inherited condition which causes progressive fibrous repair of type IV collagen in the body?
Alport syndrome
Define growth factor:
Polypeptide coded for by proto-oncogenes, which act on specific cell surface receptors, stimulating gene transcription
In what types of cells does Epidermal Growth Factor cause mitosis?
- Epithelial cells
- Hepatocytes
- Fibroblasts
What type of cells produce Epidermal Growth Factor?
- Keratinocytes
- Inflammatory cells (ie macrophages)
What does VEGF stand for?
Vascular Endothelial Growth Factor
What does VEGF cause?
- Angiogenesis
- Vasculogenesis
- Chronic inflammation
- Wound healing
Define vasculogenesis:
Process of new blood vessel formation during embryonic development of the CVS
What does PDGF stand for?
Platelet Derived Growth Factor
Which cells can produce/release PDGF?
- Platelets
- Macrophages
- Smooth muscle cells
- Endothelial cells
- Tumour cells
What is the role of PDGF?
Causes migration and proliferation of fibroblasts, smooth muscle cells and monocytes
What does G-CSF stand for?
Granulocyte-Colony Stimulating Factor
What is the role of G-CSF?
Stimulates bone marrow to produce granulocytes (ie neutrophils)