Normal Heart and Circulation

Location and Structures

The heart is a muscular, four-chambered organ. It is normally about the size of your fist. It sits just behind and to the left of the sternal bone (the chest bone) in the pleural cavity (the part of your body that holds the heart and lungs) called the mediastinum. The two upper chambers of the heart are called the atria and the two lower pumping chambers are called the ventricles.

The wall that separates the atria and the ventricles into right and left sides is called the septum. Blood is pumped through the heart with the help of four heart valves that prevent back flow and keep the blood moving in the appropriate direction. These four valves are:

  • The tricuspid valve, located between the right atrium and the right ventricle
  • The pulmonary valve, located between the right ventricle and the pulmonary artery
  • The mitral valve, located between the left atrium and left ventricle
  • The aortic valve, located between the left ventricle and the aorta.

The mitral valve normally has two flaps (also referred to as cusps or leaflets). The remaining valves normally have three flaps.

Blood Supply and Circulation

There are five major blood vessels that communicate to and from the heart. The inferior vena cava and the superior vena cava collect blood from the venous circulation (commonly referred to as "blue" blood or blood that is oxygen-poor) and return it to the right side of the heart. The blood is emptied into the right atrium, through the tricuspid valve to the right ventricle, then to the lungs via the pulmonary artery. In the lungs, the blood collects oxygen (commonly referred to as "red" blood), releases carbon dioxide and then is returned to the left atrium via four pulmonary veins. From there, blood goes through the mitral valve to the left ventricle and is pumped under high pressure by the left ventricle out to the body via the aorta.

The Heart Beat and Electrical System

The heart has an automatic conduction system that signals each beat. This inherent pacemaker system is called the sinus node located within the right atrial wall. The sinoatrial node produces an electrical impulse that travels to a central conduction site called the AV node and is then sent down to the ventricular muscle. This in turn causes a contraction of the ventricular muscle ejecting blood to both the lungs and the aorta. The number of contractions each minute is what is referred to as the heart rate or pulse. In newborns and young children, this heart rate is much faster (100-170 beats/minute) than in older children or adults (70-100 beats/minute).

Blog
More Blogs

Understanding Heart Screenings for Your Young…

November 18th, 2013 | Soccer. Baseball. Basketball. Gymnastics. If your child plans to participate in an organized sport activity, they’ll need more than just the required gear and equipment; They’ll also need a yearly physical exam. While an annual physical is fairly comprehensive, your physician may recommend additional screening for heart-related… Continue Reading

Cholesterol and Your Child

November 13th, 2013 | As adults, we know we need to watch our cholesterol in order to maintain good health. But did you know that children can have high cholesterol, too? As a parent, you can take steps today to monitor your child’s cholesterol and reduce your child’s risk of developing cardiovascular disease later in life. How Do I Know if My Child… Continue Reading

Newborn Heart Screenings: Peace of Mind

November 11th, 2013 | If you’re expecting a baby, you are hoping to leave the hospital with a healthy baby in tow. One way health care providers are helping ensure your baby is healthy and strong enough to go home is through routine newborn heart screenings. As part of Indiana law, all newborns are required to have blood oxygen levels tested before leaving… Continue Reading

Share