arterial and venous thrombosis Flashcards
(40 cards)
Why don’t blood clots form all the time?
reasons from lecture: 1. laminar flow - cells travel un the centre of a vessel and don't come into contact with the walls 2. endothelial cells are not sticky when healthy reasons from last year endothelial cells, anticoagulant pathway and fibrinolytic pathway keep it fluid platelets and coagulation proteins circulate in an inactive form
what is the definition of thrombosis?
solid mass of blood constituents formed within intact vascular system during life
What are the components of Virchow’s triad?
- change in vessel wall
- change in blood flow
- change in blood constituents
What is the first stage of thrombosis?
platelet aggregation
What type of feedback does thrombosis involve?
positive feedback
What protein is formed as a product of the clotting cascade?
fibrin
Which cascade does platelet activation trigger?
coagulation cascade
Referring to Virchow’s triad, what does smoking cause?
change in vessel wall
change in blood flow (over the injured/absent cells)
What interventions in hospital can reduce risk of thrombosis?
early mobilisation after operation
low dose subcutaneous heparin
venous stockings
According to Virchow’s triad, what is venous thrombosis due to?
change in blood flow (stasis of blood)
How does aspirin work?
Inhibits platelet aggregation - antiplatelet drug, irreversibly inhibtis COX to reduce production of pro-aggregatory factor thromboxane from arachidonic acid.
What is an embolus?
mass of material in the vascular system able to become lodges within a vessel and block it
How does a DVT embolise?
The distal part of the thrombus breaks off and travels to the vena cava, then right side of the heart and then to the lungs - pulmonary arteries
What are the other types of embolism other than that from thrombosis?
air (pressurised systems of IV fluids/blood in infants and children)
cholesterol crystals (from an atheromatous plaque)
tumour
amniotic fluid (may happen in women with precipitate labour - i.e. very fast labour)
fat (severe trauma with multiple fractures)
Where do arterial thrombi embolise to?
if the thrombus is in the heart, the embolus can travel anywhere in the systemic circulation e.g. lower limb and renal arteries
Give examples of complications of arterial thrombi
stroke
heart attack
Give an example of complication of a venous thrombus
PE
How does thrombosis occur on top of an atheroma?
The plaque ruptures, exposing collagen, leading to platelet aggregation and activation of the clotting cascade
Why is oedema seen with venous thrombosis?
impaired venous drainage
What do alpha granules contain?
substances involved in platelet adhesion such as fibrinogen, fibrognectin, platelet derived growth factor
What do dense granules contain?
ADP
Name two factors that cause platelets to degranulate when they come into contact with the substance?
fibrin
collagen
Describe the steps of arterial thrombosis
- turbulent flow (e.g. caused by endothelial damage or a plaque)
- leads to loss of endothelial cells
- exposure of underlying collagen
- platelet activation
- fibrin deposition
- RBCs trapped
- alternating layers of platelets and RBCs in fibrin mesh
Describe the steps of venous thrombosis
- low blood pressure in veins
- valves produce turbulence
- thrombi form due to endothelial damage, exposure of collagen, activation of platelets, fibrin formation, trapping of RBCs
in lec - if BP drops, then cells settle to the bottom of a vessel, so no longer laminar flow
