Hemostasis Flashcards
What are some anti-thrombotic mechanisms of the endothelium that prevent platelet accumulation?
What factor stimulates the release of these chemicals?
Prostacyclin (PGI2)
Nitric Oxide
Stimulated by Thrombin and several other cytokines.
Adenosine diphosphatase breaks down ADP inhibiting aggregation of platelets.
These are important for maintaining blood fluidity.
What do heparin-like molecules do?
These are cofactors of antithrombin, released from endothelium used to maintain blood fluidity when there is no damage.
What does Thrombomodulin do?
Tissue plasminogen activator? tPA
Converts thrombin into an anticoagulant. Is released from endothelium.
tPA is also made in the endothelial cells and is fibrinolytic by activating plasmin formation.
Endothelial cells produce what substance that aids in platelet binding after an injury?
von Willebrand factor!
What is tissue factor responsible for, where is it released and what are some scenarios that stimulate its release?
Tissue factor is released from endothelial cells and can be induced by cytokines and endotoxin.
Its repsonsibility is to promote the formation of fibrin.
What is the importance of plasminogen activator inhibitor and where is it released?
This is released from endothelial cells and ensures that fibrin will not be broken down prematurely during repair as plasmin cuts fibrin.
What is the origin of platelet cells?
Fragmentation of precursor megakaryocytes containing alpha granules and dense granules.
What molecule is important in linking the subendothelium to glycoprotein Ib receptors on platelets?
Von Willebrand Factor, leading to activation and adherence of the platelet cell.
What chemicals are found within the platelet granules?
Calcium - Important for clotting cascade.
ADP - increases platelet aggregation.
Platelet Factor 4 - Inhibits Heparin
Serotonin - Induces vasoconstriction.
What roles do ADP and calcium play and where are they ultimately released?
Released by platelet cells, calcium aids in the clotting cascade and ADP aids in aggregation of platelets.
What role does Platelet factor 4 and Serotonin play in the blood?
Released from activated platelets, Platelet factor 4 binds heparin and inhibits it.
Serotonin helps to constrict the damaged blood vessel to minimalize blood loss.
What effect does Thromboxane have in the blood?
Acts in co-ordinance with ADP to increase platelet aggregation.
What protein is responsible for linking activated platelet cells together and how are they tethered?
They are brought together by fibrinogen tied into GpIIb-IIIa.
Thrombin is then able to swoop into the action and form the plug.
What are the functions of Thrombin?
Converts fibrinogen to fibrin but also has a profound effect on local vasculature, inflammation, and fibrinolysis.
What chemical initiates the internal clotting cascade?
Hagemans factor released from damage to the basement membrane (XII)
