fibrinolytic system & thrombosis

Question 1

What does t-PA stand for?

Answer 1

• tissue plasminogen activator

Question 2

what is plasminogen?

Answer 2

a plasma proenzyme that gets converted into another enzyme

Question 3

How does plasminogen get converted to plasmin?

Answer 3

• plasminogen is activated to the active enzyme plasmin by protein plasminogen activators

Question 4

What is the function of plasmin?

Answer 4

it is a serine protease which dissolves fibrin

Question 5

what is the function of the fibrinolytic system?

Answer 5

it dissolves a clot after it has been formed

Question 6

What is t-PA secreted by?

Answer 6

• the endothelial cells of the blood vessel

Question 7

Describe the action of t-PA

Answer 7

• during clotting, both plasminogen and t-PA bind to fibrin and become incorporated into the clot
• the binding of t-PA to fibrin is crucial as it is a weak enzyme
• therefore fibrin increases the ability of t-PA to catalyse the generation of plasmin from plasminogen

Question 8

What is thrombosis?

Answer 8

a pathological condition involving a clot formation inside the blood vessel

Question 9

how does venous thrombosis occur?

using DVT and Pulmonary embolism as EG

Answer 9

• fragments of thrombi formed in the deep veinscan be carried by the blood stream through the right heart into pulmonary arteries
• these thrombus fragments can block the blood flow through the lungs
• deep vein thrombosis involves clot forming in lower limbs
• eg pulmonary embolism and deep vein thrombosis

Question 10

What does arterial thrombosis lead to?

give examples

Answer 10

it leads to local tissue damage depending on the organ/artery involved
eg: thrombus formation in the coronary arteries leads to myocardial infarction and thrombus formation in the cerebral arteries can cause stroke