Your heart is a muscle situated between the lungs and enclosed in the cavity of the pericardium. The pericardium is a membranous sac which surrounds the heart and the end portions of the aorta (large artery) and pulmonary (relating to the lungs) vein. This area is protected by the sternum (breastbone) and the cartilage of the upper and mid-portions of the rib cage. An adult's heart is approximately 5 inches in size and is larger than an adult's fist. In men, the average weight of the heart is 10 to 12 ounces and in women, the average weight is 8 to 10 ounces. 

The heart has four chambers -- the right and left atria and the right and left ventricles... 

HEART TOUR: