Can any doc tell me what's the function of your cardiac muscle?

Heart is a muscle.: Cardiac muscle contracts and relaxes known as heart beats. This sends blood entering into the heart to flow out into major blood vessels; the thoracic aorta and the main pulmonary artery. Blood from lungs enters heart via pulmonary veins and is pumped into the aorta delivering oxygen to body. Oxygen poor blood from body enters heart via vena cavae and pumped into lungs via pulmonary artery.