Session 5 Lecture Notes Flashcards
What is the definition of thrombus?
The formation of a solid mass of blood within the circulatory system
What are lines of Zahn?
Lines of the thrombus of different intensities - it varies depending on number of RBCs at a given time
What are darker in colour - arterial or venous thrombi?
Venous because they have a higher cell content
What is lysis of a thrombus and how does it take place?
Lysis = thrombus is broken down and vessel flow returns to normal
Plasmin breaks down the fibrin clot (via the fibrinolytic system)
What is propagation of a thrombus?
In what direction (to or from the heart) does it travel in which vessels?
Progressive spread of the thrombus
It spreads towards the heart in veins and away in arteries
What is organisation of thrombosis?
A reparative process where fibroblasts and capillaries replace the thrombus
However the vessel remains occluded and you don’t have normal blood flow
What is recanalisation of a thrombus?
Following organisation of a thrombus (i.e. when fibroblasts and capillaries produce CT to replace the clot), a new vascular channel grows through the CT so some blood flow is established
Lumen is still much smaller than its original size
What is the definition of an embolism?
What % are caused by thrombus?
The blockage of a blood vessel by solid, liquid or gas at a point distant from its origin
90% caused by thrombus
If a systemic vein thrombus embolises where would it end up?
In the lungs (pulmonary embolism)
If a thrombus formed in the LA or LV and embolised where would it go?
Out the aorta and into other arteries around the body
If a carotid artery had a thombus that embolised where would this end up?
In the brain
If an abdominal aorta had a thrombus that embolised where would this end up?
In the arteries of the legs
What is a massive PE?
A 60% reduction in blood flow
What is a major PE?
When medium sized vessels are blocked
What is a minor PE?
When peripheral pulmonary arteries are blocked
What is an iatrogenic embolism?
When something accidentally injected into the blood embolises
What is a fat embolism and when does it usually occur?
It usually occurs following a long bone fracture when bone marrow containing fat is released into the bloodstream a
What is haemostasis?
Haemostasis = the human body’s response to blood vessel injury and bleeding
It involves a coordinated effort between platelets and blood clotting factors to form a blood clot and prevent bleeding
Explain the 3 stages of haemostasis
- Platelets aggregate to injured vessel wall and form a clot
- Thrombin cleaves fibrinogen to fibrin forming a more stable clot
- Roughly 24 hours later the fibrin is broken down by plasmin (fibrolysis) and the degradation products are removed
What bone marrow cells are responsible for platelet production?
Megakaryocytes
What is the normal life span of platelets?
What is the normal life span of RBCs?
Platelets = 7-10 days RBCs = 120 days
When damaged tissue is exposed it reveals collagen. Platelets adhere to collagen via what receptor?
vWF receptor
Where are clotting factors made?
In the liver
What is exposed in tissue walls to activate factor 7?
Tissue factor
What is Von Willebrand factor involved in?
Platelet adhesion to the vessel wall, platelet aggregation and it also carries factor 8
What does plasmin break the fibrin clot down into?
D dimers
Name 3 natural anticoagulants
Protein C
Protein S
Antithrombin
Name two congenital coagulation factor disorders
1. Haemophilia Haemophilia A = deficiency in factor 8 Haemophilia B = deficiency in factor 9 2. Von Willebrand's disease (needed for platelet adhesion and carries factor 8)
Name some acquired coagulation factor disorders
- Liver disease (as coagulation factors are produced in liver)
- Vit K deficiency - needed for metabolism of some clotting factors
- Anticoagulants such as warfarin inhibit Vit K
What is the most common immune destruction cause of low platelet numbers?
Immune thrombocytopenia purpura
Autoantibodies are made against glycoproteins on platelet surface
When do you start to see symptoms of thrombocytopenia?
When the platelet count is less than 30
You may see small bleeds into the skin and easy bruising
