Question

What name is given to the sac, which surrounds and protects the heart?

Answer 1

The sac which surrounds the heart is called the PERICARDIUM

Explanation:

Here is the dictionary definition of "pericardium"
per·i·car·di·um
The membrane enclosing the heart, consisting of an outer fibrous layer and an inner double layer of serous membrane.

Here is a graphic showing the pericardium around the heart