The heart is located in center in the chest cavity just beneath the sternum or breastbone between the left and right lungs. The heart is enclosed in a double-walled protective sac called the pericardium, which anchors it to supporting structures and reduces friction while it beats.
The pericardium also prevents it from overexpanding. Together with the sternum, they form the body’s protective cage of the heart. The heart consists of four chambers called atria and ventricles. Oxygen-depleted blood enters through the right atrium and is pumped to the lungs through the right ventricle. From the lungs, oxygen-replenished blood enters the heart through the left atrium and is pumped to the rest of the body through the left ventricle.