Blood clotting Flashcards
How many haemorrhage classes are there?
4
What is the volume of class 1 haemorrhage and what is the effect?
Up to 15% blood volume
No medical intervention needed
What is the blood volume of class 2 haemorrhage and what are the effect?
15 - 30% blood volume
Rapid heart rate, blood pressure variances, pale and cool skin
Saline solution given
What is the blood volume of class 3 haemorrhage and what are the effects?
30 - 40% blood volume
BP drops, HR increases, brain function decreased
Saline solution and blood transfusion
What is the blood volume of a class 4 haemorrhage and what are the effects?
> 40% blood volume lost
Dead ting
Resuscitation required
What is haemostasis? (3)
Vascular spasm (reduces flow through vessel)
Formation of a platelet plug
Formation of a blood clot
What is a vascular spasm? (3)
Damage to the blood vessel
Increases resistance to blood flow
Damage activates sympathetic nervous system - vasoconstriction
What are the cellular components of human blood? (8)
Erythrocytes Leukocytes Neutrophils Eosinphils Basophils Monocytes Lymphocytes Platelets
What are platelets and what do they contain? (3)
Colourless cell fragments that break off from the megakaryocytes
Mitochondria, SER, cytoplasmic granules, NO nucleus
100,000 per ml
What is the structural difference between an active and inactive platelet?
Active - spiky outer surface and adherence to each other
Inactive - small cell fragments circular
What is the von Willibrand factor?
vWf is secreted by megakaryocytes, platelets and endothelial cells - bind to exposed collagen
How is the platelet plug formed?
vWf binds to exposed collagen
Platelets bind to vWf and this triggers adherence
Platelets secrete: Serotonin, Epinephrine, ADP
What are the 3 things platelets secrete once bound to vWf and what do they do?
Serotonin
Epinephrine
ADP - stimulates thromboxane A2 - TXA2 to promote further platelets
What stops clots blocking the whole blood vessel? (2) And what starts it?
Prostacyclin
Nitric acid
Thromboxane A2 (TXA2) causes the platelet plug formation!
What are the 7 main factors involved in platelet function and what are their roles?
Collagen - binds to platelets to begin plug
von Willibrand factor - links platelets to collagen
Serotonin - platelet aggregation
Adenosine diphosphate - platelet aggregation
Platelet-activating factor - platelet aggregation
Thromboxane A2 - platelet aggregation
Platelet-derived growth factor - Promotes healing
What is a fibrin clot? (4)
Fibrinogen is essential for clot formation
Fibrin clot formation is secondary to platelet plug
Requires activated platelets and their secretary products
All triggered by the coagulation cascade
What are the 2 pathways that begin the coagulation cascade?
Intrinsic and extrinsic
Describe the intrinsic pathway: (3)
XII –> Active XII
Active XII + XI + thrombin + Ca2+ –> Active XI
Active XI + IX + Ca2+ –> Active IX
Describe the extrinsic pathway:
VII + active X –> Active VII
Describe the common pathway that leads after intrinsic/extrinsic? (4)
X + Ca2+ –> Active X
Active X + prothrombin + Ca2+ –> Thrombin
Thrombin + Fibrinogen –> Fibrin
Fibrin + Active XIII + Ca2+ —-> Cross-linked fibrin
What are the 8 factors involved in coagulation?
Collagen - starts intrinsic pathway
vWf - regulates level of factor VIII
Tissue factor - starts extrinsic pathway
Prothrombin and thrombin - fibrin production
Fibrinogen and fiblin - Insoluble fibers to stabilize platelet plug
Fibrin-stabilising factor - cross links for stable mesh
Ca2+ - required for most steps
Vitamin K - needed for synthesis of factors
How is a clot removed? (2)2
When clot formation is activated, so is plasmin
Plasmin gets trapped in the clot and slowly dissolves it
What prevents coagulation from continuing until the vessel is fully blocked? (3)
Inhibition of platelet adhesion
Inhibition of fibrin production
Endothelial cells release anticoagulants (heparin and antithrombin 3)
What 2 molecules do endothelial cells release?
Heparin
Antithrombin 3
What does warfarin do?
Removes calcium and Active X
What are 3 anticoagulant drugs and why are they prescribed?
They are prescribed to stop blood clots forming in major organs
Coumarin anticoaggulants (warfarin) - blocks vitamin K Ca2+ removal Acetylsalicyclic acid (aspirin) - inhibits COX enzymes thromboxane A2
What is the role of aspirin in blocking platelet plug formation?
Blocks TXA2 production when platelets coagulate
What can cause coagulation disorders? (6)
Liver disease Hepatitis Cirrhosis Vitamin K deficiency Haemophilia Low blood platelets
What is haemophilia? (2)
Factor VIII deficiency
Recessive sex linked
