an adult human's heart is about the size of clenched fist. the heart lies in the chest between the two lungs. the heart is a muscular organ with walls made of cardiac muscles. the coronary arteries supply nutrients and oxygen to the muscles while the coronary veins remove wastes from the muscle.
the heart is divided into four c. the two upper chambers are called auricles or atria and the two lower chambers are called ventricles. the septum divides the heart into the right and left halves.