Multiple choice

As the blood flows out of a damaged blood vessel, the blood platelets release a substance called _______.

  1. thrombin

  2. prothrombin

  3. thromboplastin

  4. fibrin
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When a blood vessel is damaged, platelets disintegrate and release thromboplastin. This substance initiates the clotting cascade by converting prothrombin to thrombin.

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