Clotting Flashcards
define thrombosis
solid mass of blood constituents formed within an intact vascular system
what factors predispose to thrombosis
Virchoffs triangle
Blood flow change (laminar→ turbulent) (stasis)
Change in vessel wall (endothelial cell injury) (smoking causes damage)
Hypercoagulable state (inherited) (COCP)
define embolus
mass of material in the vascular system able to become lodged within a vessel and block it
define ischaemia
reduction in blood flow
define infarction
reduction in blood flow leading to cell death
what causes infarction
Ischaemia and low O2
which organs are supplied by end arteries
kidneys
liver
spleen
lung
brain
retina
what are platelets
Platelets are colourless anucleate cell fragments containing granules. They are produced when cytoplasmic portions of large bone marrow cells - megakaryocytes - pinch off and enter circulation
overview of how a thrombus forms
- vwf –> platelt plug
- Clotting cascade –> fibrin web
platelet plug formation
- vwf is released by endothelial cells and binds to exposed collagen
- circualting platelets bind to vwf
- activation and aggregation
- platelet plug contracts due to myosin and actin within
what does VWF do in platelet plug
provides a bridge to collagen and allows platelets to activate
what does thromboxane do, platelet plug
stimulates platelets to express TP receptors that allow fibrinogen to bind. also stimulaes vasoconstriction
what does ADP do, platelet plug
activates platelets
what does fibrinogen do
aggregates platelets
what does the liver do which is important for clotting?
produces clotting factors 10, 9,7,2
produces bile salts needed for absorption of vitamin K (needed for production of 10, 9, 7, 2)
what is overall role of coagulation proteins
to convert soluble fibrinogen into insoluble fibrin
what is the key enzyme in clotting cascade
thrombin (factor 2a) -
catylases convertion of fibrinogen to fibrin
what are platelets and proteins activated by?
tissue factor - on cells other than endothelium
What is the intrinsic pathway activated by? what factors involved?
The intrinsic pathway is activated by contact with a damaged surface and goes as follows:
Factor XII → Factor XI → Factor IX (+ Factor VIII + vWF) → Common pathway
what is the extrinsic pathway activated by? what factors involved?
The extrinsic pathway is activated by the release of tissue factors and goes as follows:
Factor VII → Common pathway
what factors are involved in the combined pathway?
The combined pathway then proceeds the intrinsic/extrinsic pathways and goes as follows:
Factor X (+ Factor V) → Factor II → Factor I (+ Factor XIII → Fibrin mesh)
