C. S. Mott Children's Hospital
Normal Heart
The normal heart sits in the chest, slightly more toward the left, with the tip or "apex" pointing towards the left side.
The heart grows throughout childhood, and is the size of a person's hands wrapped around each other, so you can see just how small a baby's heart really is!
The heart is a basically a pump. It pumps blood to the lungs to pick up oxygen and drop- off carbon dioxide. It pumps blood to the body to provide needed nutrients and pick-up waste products.
The heart has four chambers, two upper chambers, called the atria and two lower chambers called the ventricles. There is a right atrium (1), a right ventricle (2), a left atrium (3), and a left ventricle (4). The upper chambers, the atria, collect the blood as it returns to the heart. This blood is pumped to the lower chambers. The blood in the right ventricle is pumped to the lungs and the blood in the left ventricle is pumped blood to the body.
The heart also has four heart valves. The valves are thin flaps of tissues anchored in a fibrous ring and their purpose is to keep blood moving in a forward direction. The valves open to allow blood pass through and close to prevent backward blood flow. The tricuspid valve (5) sits between the right atrium and the right ventricle. The pulmonary valve (6) sits between the right ventricle and the pulmonary artery. The mitral valve (7) sits between the left atrium and the left ventricle and the aortic valve (8) sits between the left ventricle and the aorta.
The electrical system of the heart keeps the heart beating in an organized manner at a rate that meets the body's needs. Click on Keeping the Beat for more information about the heart's electrical system.
Blood enters the heart through large veins called the superior vena cava (9) and the inferior vena cava (10). Blood exits the right heart through a large blood vessel called the main pulmonary artery (11) that branches into the right and left pulmonary arteries supplying blood to the right and left lungs. After flowing by the lungs, the blood returns to the left atrium via four pulmonary veins (12). The blood exits the left heart through a large blood vessel called the aorta (13).
Putting it all together, blue blood returning from the body goes to the right atrium through the tricuspid valve to the right ventricle, through the pulmonary valve, out the pulmonary artery to the lungs where is picks up oxygen. The red, oxygen-rich blood returns from the lungs through four pulmonary veins to the left atrium, through the mitral valve, to the left ventricle, through the aortic valve, and out the aorta to the body.
