Thomosis, Embolism, Ischaemia, And Infaction Flashcards
Why don’t blood cloths form all the time?
- Laminar flow - cells travel in the centre of the arterial vessels and don’t touch the sides
- Endothelial cells which line vessels are not sticky when healthy - Teflon coating (nitric oxide)
What is thrombosis?
The formation of a solid mass from blood constituents in an intact vessel (or vascular system) in a living person (mostly platelets)
It is different from a clot which is blood coagulated outside of the vascular system or after death
Thrombus formation steps
- Turbulence causes damage to the endothelial cells in the vessels causes some of the cell to lift away from the vessel wall, exposing collagen
- VASOSPASM = activated platelets secrete serotonin to cause vasospasm and reduce blood flow
- PRIMARY PLATELET PLUG: VWF binds to this exposed collagen, and platelets bind to this and release the chemicals which causes ‘platelet aggregation’ also starts off the cascade of clotting proteins in the blood
- gp1b activation
- gp 2a/3b activation - Red blood cells then get trapped within the aggregation platelets
- COAGULATION CASCADE: Clotting factors (fibrin polymerises to fibrinogen) join the red blood cells and platelets, and the clotting cascade forms a large protein molecule fibrin, which then gets deposited and forms the clot
- Intrinsic = 12, 11, 9, 8
- Extrinsic = 7 + 3
- Common = 10, 5, 2 ,1 - Positive feedback loop -> can end up causing a thrombus, blocking the artery.
Thrombi will grow in the direction of blood flow = PROPOGATION
What are the causes of a thrombosis?
Virchows Triad:
- Change in vessel wall (endothelial injury)
- Change in blood flow = AF, Immobility
- Change in blood continuances (hyper coagulability) = sepsis (DIC), atherosclerosis, COCP, pregnant, malignancy
What medication can reduce the risk of thrombus formation?
Low dose aspirin inhibits platelet aggregation, so this can be prescribed to reduce the risk of thrombosis
What is an embolism?
The process of a solid mass in the blood being carried through the circulation to a place where it gets stuck and blocks the vessels.
What is an embolus?
A mass of material in the vascular system able to become lodged within a vessel and block it
Commonest mass of embolus is a thrombus
Causes of an embolism?
Usually caused by a part of a thrombus that has broken off and circulates in the blood stream (only small blood vessels can become blocked)
Less common causes are:
- infective endocarditis
- air
- tumour
- amniotic fluid
- fat (severe trauma with fractures)
Where does an embolus travel in the venous system?
If an embolus enters the venous system, it will travel to the vena cava and lodge in the PULMONARY CIRCULATION from the right side of the heart. The lungs then act as a filter for venous emboli, because the blood vessels split down the capillary size, which is too small for the embolus to travel though
What does an embolus travel to in the arterial system?
If an embolus enter the arterial system, it can travel anywhere downstream of its entry point in the SYSTEMIC CIRCULATION from the left side of the heart
What is ischeamia?
Reduction of blood flow to a tissue without any other implications (WITHOUT INFARCTION)
Infarction
A reduction of blood flow to a tissue that’s so reduced that it can’t even support maintenance of the cells in that tissue so they die (WITH INFARCTION)
What is end artery supply?
When an organ that only receives blood supply from one artery
Why are end arterial supplies problematic?
When a thrombus forms, because the whole blood supply to that organ is cut off leading to infarction.
Examples of organs which have multiple arterial supplies
Pulmonary arteries and bronchial arteries supplying the lungs
Portal vein and hepatic artery supplying the liver
Some parts of the brain - circle of Willis
