The human heart is surrounded by a wall of muscle consisting of a singular muscle type, that being cardiac muscle, which could be argued to be among the strongest muscle tissue of the three types. The heart pumps, on average, about 70-72 times. The human body has about 5-5.6 quarts of blood that is circulated by the heart every three minutes. Heart tissue has the greatest number of mitochondria, the energy "powerhouses" that supply energy requirements for the heart cell. The heart consists of two upper chambers that receive blood, called atria, and two lower chambers that contract and send the blood, called ventricles.
1 muscle, the cardiac muscle