Multiple choice general knowledge science & technology The fluid filled sac that surrounds the heart is called the- myocardium ventricle septum pericardium Reveal answer Fill a bubble to check yourself D Correct answer Explanation The pericardium is a protective, fluid-filled double-layered sac that encloses the heart and reduces friction during heartbeat. Myocardium is heart muscle tissue, ventricle is a chamber, and septum is the dividing wall between heart chambers.