Multiple Choice
What is the primary function of a platelet plug in hemostasis?
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17. The Blood
Platelets: Hemostasis
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In the process of hemostasis, which of the following substances normally helps keep blood from clotting in intact, uninjured vessels?
A
Thromboxane A2 (TXA2) released by activated platelets
B
Fibrin formed from fibrinogen
C
von Willebrand factor (vWF) mediating platelet adhesion
D
Prostacyclin (PGI2) released by endothelial cells
Verified step by step guidance1
Step 1: Understand the process of hemostasis, which involves stopping bleeding by forming a clot at the site of vessel injury while preventing clotting in intact vessels.
Step 2: Identify the role of substances released by different cells during hemostasis. For example, activated platelets release Thromboxane A2 (TXA2), which promotes clotting, and fibrinogen is converted to fibrin to form the clot mesh.
Step 3: Recognize that von Willebrand factor (vWF) helps platelets adhere to the damaged vessel wall, promoting clot formation at injury sites.
Step 4: Focus on substances that prevent clotting in uninjured vessels. Prostacyclin (PGI2), released by endothelial cells lining intact blood vessels, inhibits platelet activation and aggregation, thus preventing clot formation where it is not needed.
Step 5: Conclude that Prostacyclin (PGI2) is the key substance that normally helps keep blood from clotting in intact, uninjured vessels by counteracting platelet activation.
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