Why does the blood not boil immediately within the closed circulatory system?

Answer

The blood vessels maintain enough pressure to keep the boiling point above body temperature

The structural integrity and pressure maintained by the closed circulatory system resist the vacuum enough to keep the blood pressure above the liquid’s boiling point for a short while.

Why does the blood not boil immediately within the closed circulatory system?
Spacedeathhumanexposurevacuum