4. Healing and Repair Flashcards
What do neutrophils and macrophages do in repair?
Phagocytose debris
When does fibrosis repair occur?
When permanent cells undergo necrosis
When labile/stable cell’s collagen framework is destroyed
What are the chemical mediators in repair?
Lymphocytes and macrophages
What do fibroblasts and myofriboblasts do in repair?
Produce collagen
Wound contraction
Name an angiogenesis growth factor and what does it do?
VEGF
Causes existing vessels to sprout new vessels via endothelial proliferation
(This is exploited in malignant neoplasms)
What does extracellular matrix do?
Supports and anchors cells Separates tissue compartments Sequesters growth factors Allows communication between cells Facilitates cell migration
What is the mechanism of fibrous repair?
Inflammatory cells infiltrate - forms a blood clot + inflammation
Clot is replaced by granulation tissue (capillaries and myofibroblasts)
Collagen increases, myofibroblasts contract and vessels reduce in number leaving a fibrous scar
Define unipotent
Can only produce one type of differentiated cell such as epithelial cells
Define multipotent
Can produce several types of differentiated cell such as haematopoietic cells
Define totipotent
Can become any type of cell such as embryonic stem cells
Define labile cells
Rapid proliferation, active cell division
Give an example a of a labile cell
Epithelia
Haematopoietic cells
Define stable cells
In the resting state, G0
Proliferation speed variable
Give an example of stable cells
Hepatocytes
Osteoblasts
Fibroblasts
Define permanent cells
Unable to divide or regenerate
Cannot leave G0
Give an example of permanent cells
Cardiac myocytes
CNS neurones
Define autocrine
Cell produces hormones that effect itself
Define paracrine
Hormones produced effect local tissue
Define endocrine
Hormones produced travel in the blood to effect tissues elsewhere in the body
Name some growth factors
Testosterone Oestrogen GH PDGH EGF
How does contact affect proliferation?
Contact inhibition inhibits proliferation in intact tissue, loss of contact promotes proliferation
This is exploited in cancer
How is a clean incised skin wound with apposed edges healed?
Primary intention
Describe healing by primary intention
Minimal clotting or granulation
Epidermis regenerates
Dermis undergoes fibrous repair leaving a scar
Risk of a trapped infection leading to abscess
How does a large skin defect heal?
Secondary intention
Describe healing by secondary intention
Scabs over Epidermis regenerates from the base up Produces granulation tissue Wound contracts to reduce the size of the defect Leaves a large scar
Name local factors impacting healing and repair
Type, size, location Apposition Blood supply Infection Foreign material Radiation damage
Name general factors impacting healing and repair
Age Drugs Dietary deficiencies such as protein Specific dietary deficiencies such as vitamin c or essential amino acids Diabetes Cardiovascular status
How does cardiac tissue heal?
Fibrosis
How does bone heal?
Callous formation
How does the liver heal acute and chronically?
Acute - regenerates
Chronic - fibrosis
How do peripheral nerves heal?
Distal - Wallerian degeneration
Proximal - degeneration with distal proliferation
How does CNS heal?
No regeneration but glial cells can proliferate
How does smooth muscle heal?
Regenerates via dividing
How does skeletal muscle heal?
Satellite cells fuse with fibres
