Primary & Secondary Haemostasis Flashcards
How long does Primary Haemostasis lasts in humans?
10 days
Describe the structure of platelets?
Non- nuncleated biconvex disc
Where are platelets produced?
In the bone marrow by fragmentation of the cytoplasm of megakaryocytes
What is the main regulator of platelet formation ?
Thrombopoetin
Where is thrombropoetin produced?
In the liver
What is Haemostatsis?
It is the cessation of blood flow through a blood vessel or body tissue and is the physiologic end point after injury to a vessel wall or tissue.
Which substances are natural inhibitors of platelet aggregation?
Nitric Oxide
Prostacyclin (PGI2)
ADP dephosphotases (CD39 - Ectonucleotidase)
They act as vasodilators
Where are the natural inhibitors of platelet aggregation produced?
By endothelial cells
What is the normal size of platelets?
2-3 microns
What is the lifespan of platelets?
8-10 days
What is the normal platelet count?
250 × 109/L (range 150–400 × 109/L)
What is the name of the molecule that accommodates Antithrombin III?
Heparin Sulfate (Heparin)
What is the purpose of antithrombin III?
It is a serine protease inhibitors, ( it inhibits all coagulation proteins)
It inhibits Factor IIa, VIIa, IXa, Xa, XIa , XIIa and kalikrein
What is the purpose of Heparin?
It allows antithrombin III to bind to it and significantly increases its anticoagulant activity against factor IIa
What protein is activated by thrombomodulin?
Protein C
What is the purpose of Protein C?
Protein C is a vitamin K dependent molecule which INACTIVATES factors V and VIII by DECREASING the production of thrombin.
What is the purpose of Tissue plasminogen activator (tPA) found on endothelial cells?
Tissue plasminogen activator (tPA) activates PLASMINOGEN which then produces PLASMIN. Plasmin is a “fibrin cutter” it degrades fibrin into fibrin degradation products (FDP’s ) and also insoluble fibrin monomers called D-dimers”
Where is Plasminogen produced?
In the liver
Where are Von Willibrand factors stored?
Weibel–Palade bodies and platelet α granules,
Where are Von Willibrand factors (vWF) synthesised?
By endothelial cells and Megakaryocytes
True or False? vWF also circulates in the plasma bound to factor VIII, acting as a stabilizer for factor VIII.
TRUE!!
What is the function of Thrombin A2?
It serves as a vasoconstrictior and a platelet aggregator
What substance released from dense granules has a major positive feedback role in promoting platelet activation?
ADP
True or false?TXA2 increases platelet cyclic adenosine monophosphate (cAMP) levels ?
FALSE!! TXA2 DECREASES platelet cyclic denosine monophosphate (cAMP) levels
What enzyme does Aspirin inhibit?
Cyclooxygenase
Describe the role of Aspirin in platelet aggregation.
Aspirin irreversibly inhibits the platelet cyclooxygenase (COX) enzyme, thereby halting production of TXA2. Platelet count will remain normal in these patients.
What are the substances contained in Dense ( Delta ) granules?
S- Serotonin
A- ADP
C - Calcium
“That is one Dense SAC”
What is the function of Serotonin ?
Serotonin serves as a vasoconstrictor
What is the function of ADP?
ADP serves as a platelet aggregator. ADP interact with the ADP receptor found on platelets and initiates a cascade that promotes the insertion of glycoprotein IIb/IIIa receptors on the platelet surface.
What is the function of Calcium?
Allows coagulation factors to aggregate with platelets also- it helps to cross-link adjacent platelets.
What factor does factor XIIa activate?
Factor XIa(11)
Factor XIa activate?
Factor IX (9)
What is another name for Factor IX ?
Christmas Factor
What is another name for factor XII?
Haegman factor
What is the anticoagulation cascade initiated by?
By FXIIa via the activation of Plasminogen and Kininogen system
What is the Kininogen system?
The kininogen system produces kallikrein and bradykinin. Kallikrein activates the fibrinolytic system and promotes the activation of plasminogen into plasmin, whereas bradykinin acts as part of the body’s inflammatory response to increase vasodilation, vessel permeability, and pain.