The primary function of the pericardium surrounding the heart is to provide protection and support. This double-walled sac contains a lubricating fluid that reduces friction during heartbeats, facilitating smooth contractions. Additionally, the pericardium helps limit the movement of the heart within the thorax, maintaining its position and preventing excessive expansion. This structure contributes to optimal heart function, ensuring effective blood circulation throughout the body while protecting the heart from infections and physical trauma.