There is another part to this answer, and I can't tell if this is what you are really asking. The above poster is absolutely correct in the way that blood circulates throughout the body, and how the heart makes this happen. But the heart itself is a muscle that requires a large amount of oxygenated blood. Right after the aorta leaves the left ventricle, two coronary arteries emerge and provide blood to the heart muscle itself. Blockages in these arteries are what cause heart attacks. The closer the block is to the origin of the coronary artery, the larger the area of the heart that is no longer getting a blood supply, and the more likely the heart attack is to be fatal.
On average, the body has five liters of blood continually traveling through it. Blood flows through the body via the circulatory system. The circulatory system is made up largely of veins, capillaries, arteries, and the heart.
As blood begins to circulate, the heart contracts the left ventricle and blood is forced into the aorta. This blood is oxygen rich and will be pumped to all parts of the body by way of arteries. On the way back to the heart, deoxygenated blood will travel through veins. The veins bring the deoxygenated blood back to the heart by entering the right atrium, by way of the vena cavea. The right atrium fills with this blood and contracts. This contraction pushes the blood through a one-way valve into the right ventricle. The right ventricle contracts and forces the deoxygenated blood into the pulmonary artery, which leads to the lungs. While in the lungs a gas exchange occurs. During this process waste leaves the blood and oxygen enters it. This oxygenated blood then leaves the lungs through the pulmonary veins and reenters the heart through the left atrium. The heart contracts and pushes the blood through a one-way valve into the left ventricle. It is then forced into the aorta and the process repeats.
Human heart is a muscular organ which is of the size of one's fist. It has four chambers. Upper two chambers are called auricals and the lower two chambers are called ventricles. Auricals are thin walled because htey pump blood to ventricles whereas venticles are htick walled to pump blood to various organs. Walls of the heart are called pericardium.
Vena cava brings the deoxygenated blood from different parts of the body to the right aurical of the heart which then contracts and passes the blood to right ventricle. From here pulmonary artery arise which carries the blood to lungs for oxygenation. The pulmonary vein brings the oxygenated blood from lungs to left aurical which contracts and the blood is shifted to left ventricle from where aorta arises which distributes the blood to whole of the body
Heart is a an organ in bodies of humans and other animals that pumps blood for it circulation in the body. The circulation of blood in humans is divided in two distinct blood circulation network. One part of the blood circulation system pumps purified, oxygen rich blood to all parts of the body. The purified blood is received for this from the lungs. The second part of circulation system received blood with carbon dioxide after it has circulated through the body and pumps it to the lungs for purification.
The hears is like a pair of pumps in whic one pump is used for pumping the oxygen rich blood to whole body, while the other is used for pumping blood with carbon dioxide to the lungs for purification. Blood from the body containing carbon dioxide is returned to the right side of the heart and is pumped into the lungs. The oxygenated blood from the lungs flows to the left side of the heart, and is pumped to the entire body