Basics

Question 1

What cells are platelets released by

Answer 1

Platelets are normally released by megakaryocytes.

Question 2

Normal platelet count

Answer 2

Normal Plts 50-450k.

Question 3

What is the major regulator of platelets?

Answer 3

The major regulator of plts formation is TPO which is synthesized in the liver and increases with inflammation.

Question 4

What is the typically lifespan of platelets and where do they reside?

Answer 4

Typical plt lifespan in 7-10days
Plts reside in the spleen

Question 5

Explain the process of platelet clot formation

Answer 5

Starts with a vascular injury that impairs the natural antithrombolic effects of the vessel lining. Platelet adhesion is controlled by VonWilabrand Factor, a large protein that acts as a platelet “glue” and can withstand large amounts of friction and sheer. Platelets also stick together with collagen. Once platelets become activated, they release components that inhibit the natural antithrombolic state of the vessel and promote platelet aggregation. This eventually forms a platelet plug.
As the plug is forming, a fibrin mesh forms to stabilize it.

Question 6

Explain the formation of a fibrin clot

Answer 6

Either the Intrinsic, inside the body, or an Extrinsic, outside the body, cause initiates the clotting cascade.
The extrinsic pathway is associated with Tissue Factor and intrinsic is associated with contact activation.
The trigger for formation is vascular damage

Question 7

Explain the body’s natural antithrombolic features

Answer 7

Endothelial cells release prostacyclin and nitric oxide to prevent platelet aggregation and activation.
Antithrombin is a potent inhibitor of thrombin and thus prevents the formation of fibrin clots.
Protein C is an anticoagulant that is activated by thrombin
Plasmin is an enzyme of the fibrolytic system that digests fibrin.

Question 8

What are the three components to thrombocytopenia

Answer 8

• Decreased bone marrow production
• Splenic sequestration
• Increased Destruction