Healing and Repair 1. Flashcards
What is overall goal of treating inflammation?
To remove the thing that is causing the inflammation and to restore homeostasis.
Can inflammatory responses damage host tissue?
Yes.
What causes hypersensitivity diseases?
Normal immune responses where the immune system attacks antigens from the animals own body.
What antigens cause type-1 hypersensitivity reactions?
Environmental and food antigens that cause immediate and persistent release of inflammatory mediators.
What cells are involved in type-1 hypersensitivity reactions?
Mast cells.
What usually causes type-1 hypersensitivity reactions?
Allergies.
What antigens cause type-2 hypersensitivity reactions?
Antigens on the animals own body.
What part of the immune system is involved in type-2 hypersensitivity reactions?
The complement system and cytopathic antibodies.
What are cytopathic antibodies?
Antibodies formed against antigens that they shouldn’t attack.
What are type-3 hypersensitivity reactions characterised by?
The excessive formation of antigen-antibody complexes.
These block capillaries and activate the complement system.
Type-3 hypersensitivity reactions commonly cause what 2 types of inflammation?
Glomerulonephritis.
Vasculitis.
What immune cells are involved in type-4 hypersensitivity reactions?
Cytotoxic T cells.
What usually causes type-4 hypersensitivity reactions?
Cytotoxic T cells cause apoptosis in healthy cells.
What condition can arise if the pancreas is affected by a type-4 hypersensitivity reaction?
Type I diabetes mellitus.
What kind of arthritis can be caused by a type-4 hypersensitivity reaction?
Rheumatoid arthritis
How do neutrophils aid with healing?
They remove cellular debris to aid healing.
How does fibrin aid with healing?
It protects the surfaces of the tissue.
What causes recurrent inflamamtion?
Neutrophils and macrophages arriving at the same time.
What are the 2 mechanisms by which healing can occur?
Healing by regeneration.
Healing by repair.
How does healing by regeneration take place?
Dead cells are replaced by an identical cell type and tissue.
Homeostasis is restored.
How does healing by repair take place?
Dead cells must be replaced by another cell type, usually fibrous connective tissue (scar tissue).
What determines the healing process that is used?
The extent of the injury.
What must be present for healing by regeneration to take place?
The progenitor cells and underlying supportive tissue must still be present.
When does healing by repair take place?
When there is loss of progenitor cells and underlying supportive tissue.
What kind of cells have high regenerative capacity?
Labile cells.
What kind of cells have regenerative capacity when stimulated?
Stabile cells.
What kind of cells have little to no regenerative capacity?
Permanent cells.
What are labile cells?
Cells with high turnover.
Tissues that regenerate for the lifespan of the host.
E.g. Skin/gut cells.
What tissues tend to be made up of stabile cells?
Many parenchymatous organs such as the liver, kidney, pancreas etc.
Do all stabile cells have the same regenerative capacity?
No, it varies.
What are 2 things that stimulate stabile cells to regenerate?
Growth mediators.
Hormones.
When are neurons capable of repair?
If there is an intact cell body and the myelin sheath and supportive connective tissue are still present.
If the myelin sheath of a nerve is severed then what part of the nerve will be affected?
Everywhere distal to that area will be affected and will degenerate.
If the myelin sheath of a nerve is partially damaged then what part of the nerve will be affected?
The supportive connective tissue can cause regeneration.
What cells regenerate bone?
Osteoblasts.
How do bones regenerated?
A haematoma forms and clots the blood around the break.
Fibrous connective tissue comes in and osteoblasts calcify it to form bone.
Cells in what 3 areas of the body will not be able to repair themselves?
Skeletal muscle cells.
Cardiac muscle cells.
Cells in the CNS.
What kind of healing always takes place in permanent cells?
Replacement with scar tissue.
How can healing by repair damage organs?
Becuase it leaves scar tissue which means the organ cannot function properly.
Granulation tissue is a hallmark of what kind of inflammation?
Chronic inflammation.
What is granulation tissue composed of?
New blood vessels and myo-fibroblasts.
When does granulation tissue appear?
When blood vessels proliferate and grow towards the area of injury and mature into blood vessels.
The proliferation of blood vessels has what name?
Angiogenesis.
What are endothelial tubes?
The structures created when blood vessels proliferate during angiogenesis.
Why does tissue around fibroblasts start to look pink?
As the fibroblasts secrete collagen.
What kind of regenerative capacity do endothelial cells have?
They are stabile cells so they need a stimulus in order to repair.
What is granulation tissue composed of?
New blood vessels and fibrobalsts.
How do the new blood vessels and fibroblasts grow during the formation of granulation tissue?
They criss-cross each other to form a lattice formation.
What does granulation tissue form from?
Healthy tissue at the edge of a wound.
It then migrates inward and matures to fibrous scar tissue.
How does granulation/scar tissue become stronger?
As more collagen is secreted the tissue becomes stronger.
What is the function of myofibroblasts in granulation tissue formation?
They contract and bring the tissue together.
What is exuberant granulation tissue formation?
Proudflesh.
This is where the granulation tissue keeps growing as there is not stimulus to stop.
What 4 things is exuberant granulation tissue formation associated with?
Excessive movement.
Lack of soft tissue.
Infection.
Low blood supply.
What possibly leads to the lack of a stop proliferating signal in the formation of exuberant granulation tissue?
Fibroblasts fail to go through apoptosis.
What is damaged tissue in the CNS replaced with?
Reactive astrocytes and microglial cells that act as scaffolding to produce a glial scar
What is the function of a glial scar in the CNS?
It prevents axonal and neuronal growth.
