Thombosis Flashcards
What is the lining of an artery composed of?
Several endothelial cell, making a basal lamina to ‘sit on’
What is found around the basal lamina of an artery?
Smooth muscle cells
What is found around the smooth muscle cells around an artery?
Interstitial collagen fibres
What is the middle of an artery called?
Lumen
What does the lumen of an artery contain?
Red blood cells
White blood cells
Platelets
Plasma
What is the colour of platelets and what size are they?
White and small
What are platelets not normally exposed to which is important in terms of thrombosis?
Interstitial collagen fibres
What does the plasma consist of?
Water
Numerous proteins
Clotting factors
Other molecules
What is serum?
Plasma without clotting factors
Where are clotting factors produced?
Liver or by epithelial cells
How are clotting factors named?
With a roman number, such as Factor VII
What kind of system are clotting factors?
Amplification system resulting in thrombin production
What do clotting factors result in the formation of?
Thrombin
What does thrombin do?
Converts soluble fibrinogen into insoluble fibrin
What is the process of damage to the formation off fibrin known as?
Clotting cascade which is an amplification system
What does TP stand for in terms of clotting?
Tissue factor
What is the basic process of the formation of fibrin?
1) Damage to vessel
2) Tissue factor is exposed
3) Tissue factor combines with clotting factor to convert prothrombin into thrombin
4) Thrombin converts fibrinogen into fibrin
What could the initial damage of the vessel be due to?
Trauma
What does trauma causing vessel damage lead to?
1) Exposure of interstitial collagen
2) Exposure of molecule called a tissue factor
3) Blood leaks out and the serum comes into contact with the interstitial collagen fibres, where plasma clotting factors are activated
What is interstitial collagen?
Collagen in connective tissues between structures
Where are tissue factors released from?
Smooth muscle cells
What exposes and releases tissue factors from smooth muscle cells?
Trauma
What does the tissue factor do?
Binds to the clotting factor and initiates the clotting cascade
What are many clotting factors?
Serine proteases, which have serine amino acids in them and they cleave other clotting factors to form the active molecules
What do many clotting factors do?
Cleave other clotting factors to form the active molecule
What is the difference between fibrin and fibrinogen?
Fibrinogen is a small soluble molecule, whereas fibrin is a large aggregate of insoluble strands
What is the end point of the clotting cascade?
The formation of fibrin from fibrinogen
Where are platelets produced?
In bone marrow
What cells are platelets formed from?
Megakaryocyte
Why do megakaryocytes get so big?
They undergo nuclear division but not cell division so have many nuclei
How do platelets leave megakaryocytes?
Bud off as fragements from cytoplasmic extension, they are very small
What is the process of platelets working?
1) Trauma to vessel exposes platelets to interstitial collagen
2) Platelets try to form a bridge to closs the gap
What is coagulation?
Solidification of blood
What are the 2 types of coagulation?
Thrombus formation
Clot formation
Where does thrombus formation occur?
In flowing blood
What colour is a pure thrombus?
Pale cream
What does a thrombus consist of?
Platelets and a mesh like network of fibrin strands
What is thrombosis?
The process of thrombus formation which occurs in flowing blood
How to platelets adhere to interstitial collagen?
Molecules on their surface, this is how they can do so in flowing blood
What enhances the surface molecules of platelets that allow it to adhere to interstitial collagen in flowing blood?
Factor VIII
What is the process of clot formation?
1) Blood leaks out off a vessel and becomes stationary
2) Clotting cascade is activated next to the stationary blood sitting next to the interstitial collagen
3) Clot consists of network of fibrin strands and red blood cells
What is haemostasis?
Stopping bleeding
What is the process of haemostasis in normal skin with a wound?
1) Vessel in skin is surrounded by collagen
2) Blood flows through vessel in the skin
3) Trauma disrupts one side of the vessel
4) Blood leaks out
5) Clotting system is activated by collagen and by the stationary blood, forming a clot
If this does not work correctly the process goes on:
6) Vessel continues to bleed
7) Vasocontricts to decrease blood loss
8) Platelets and fibrin form thrombus to bridge the gap between the ends of the vessel adjacent to flowing blood
9) Skin stops bleeding so haemostasis has been achieved
What happens if the formation of a clot does not stop bleeding in the skin?
1) Vessel vasoconstricts to decrease blood loss
2) Platelets and fibrin form thrombus to bridge the gap between the end ends of the vessel adjacent to flowing blood
3) Skin stops bleeding so haemostasis has been achieved
What occurs in any wound due to trauma where there may be bleeding?
Vasoconstriction helps reduce bleeding
Clot formation occur in space around vessel and may fill void of wounded tissue
Thrombus forms in flowing blood and stops bleeding from gaps in vessels
What is granulation tissue?
After healing new vessels can grow into area of wound
What do the capillaries that grow in granulation tissue do?
Oxygenate the area of the wound and keep it alive
What does stagnant mean?
Stationary
When is thrombosis good?
If it allows blood to flow along the vessel
When is thrombosis bad?
If it blocks the vessel
It causes stationary blood behind it which results in clotting
What does thrombosis blocking a vessel lead to?
Ischaemiae (lack of blood flow to tissues)
Hypoxia (lack of oxygen in tissues)
What is ischaemia?
Lack of blood flow to tissues
What is hypoxia?
Lack of oxygen in tissues
What eventually happens after thrombosis?
The vessel wall repairs itself and the thrombus is removed
What is the thombus removed by?
Fibrinolytic system which removes fibrin and stops thombi from propogating
What does the fibrinolytic system do?
Removes fibrin and stops thombi from propogating
What does the fibrinolytic system depend on?
Plasma protein called plasminogen being converted to plasmin
Plasmin cutes up fibrin into fibrin degradation products
What is the precurser of plasmin?
Plasminogen
What does plasmin do?
Cuts up fibrin into fibrin degradation products
What is the fibrinolytic system normally in balance with?
The clotting system
What is important at the site of injury to limit the extent of the evolving thrombus?
Plasmin generation
What is thrombosis and clotting normal in?
Wound healing
Stopping bleeding during menstruation
Some embryonic processes
When is thrombosis and clotting abnormal?
Vessels which have abnormal walls (such as affected by atheromas)
Blood which has abnormal constituents (the clotting system or platelets are abnormal)
Abnormal flow in vessel
What are the 3 things associated with abnormal thrombosis and clotting called?
Virchow’s triad
What are the 3 things of virchow’s triad?
Abnormalities of vessel wall
Abnormalities of constituents of the blood
Abnormalities of vessel flow
What are thrombi composed of?
Platelets mixed with fibrin, forming in flowing blood
What does a clot consist of?
Fibrin admixes with red blood cells, forming in stationary blood
