Thrombosis and Embolism Flashcards
What is haemostasis?
The response of a blood vessel to injury to prevent blood loss
What is haemostasis like in healthy vessels??
Endothelial cells inhibit haemostasis by physically insulating tissue from blood, producing inhibitors of platelet activation and producing antithrombin
What are the inhibitors or platelet activation?
Nitric oxide
Prostacyclin
Which cells are involved in haemostasis?
Endothelial cells
Platelets
Clotting cascage
What is the role of endothelial cells in haemostasis?
Endothelin - vasoconstriction
Loss of barrier to expose underlying tissues - activates platelets and clotting cascade
Von Willebrand Factor - promotes platelet adhesion to ECM proteins
Thromboplastin - activates coagulation cascade
What is the role of platelets in haemostasis?
Activated by ECM proteins
Secrete thromoxane A2, vasoactive amines and ADP
What is thrombosis?
Inappropriate activation of haemostasis
What is a thrombus?
A mass formed from fibrin, platelets, RBCs and WBCs
What is the difference between a thrombus and a blood clot?
Blood clot = static blood, does not involve platelets interacting with vessel wall
What are the three components of Virchow’s Triad?
Endothelial injury
Hypercoagulability
Abnormal blood flow
What can cause changed blood flow in arteries?
TURBULENCE Narrowing of lumen Aneurysm Myocardial infarction Arrythmia
What can cause changed blood flow in veins?
STASIS
Right heart failure
Compressed veins
Blood viscosity (SCA etc)
What is the consequence of altered blood flow?
Increased coagulation
What are the genetic causes of blood constituent coagulation?
Antithrombin III deficiency
Protein C deficiency
What are the acquired causes of blood constituent coagulation?
Tissue damage
Oral contraceptives
Cigarette smoking
