The heart is a muscle about the size of your fist. The parts of the heart work together as two pumps in one. The right side of the heart receives blood from the body and sends it to the lungs. The left side of the heart receives blood from the lungs and sends it out to the body. The blood gives the body oxygen and nutrients, as well as carries waste away.

The parts of the heart fall into three broad categories:

• Chambers
• Valves
• Heart wall

Heart Chambers

The heart has four chambers. The chambers are blood-filled areas attached to major veins or arteries that bring blood to or carry blood away from the heart.

• The left and right atria are the upper two chambers that receive blood. The right atrium receives oxygen-poor blood from the two largest veins, the superior vena cava and inferior vena cava. The left atrium receives oxygen-rich blood from the pulmonary veins. Both atria then pump this blood supply into the ventricles.
• The left and right ventricles are the lower two chambers that send blood out of the heart. The right ventricle pumps oxygen-poor blood into the lungs through the pulmonary artery. The left ventricle pumps oxygen-rich blood into the body through the largest artery in the body, called the aorta.

The atria and ventricles work together. The atria fill with blood, then move blood into the ventricles. The ventricles squeeze, pumping blood out of the heart. While the ventricles squeeze, the atria then fill up with blood to ready for the next pump.

Heart Valves

The heart has four one-way valves that connect the chambers. These parts of the heart all work together, acting like doors opening and closing to keep blood flowing in the right direction. They close to keep blood from flowing backward in the wrong direction.

• These valves let blood flow from the atria to the ventricles:
  • Mitral valve: Located between the left atrium and left ventricle
  • Tricuspid valve: Located between the right atrium and right ventricle
• These valves control blood flow from the heart to the body:
  • Aortic valve: Located between the left ventricle and the aorta
  • Pulmonary valve: Located between the right ventricle and the pulmonary artery

Heart Wall

The heart wall has three layers:

• Endocardium: The thin membrane that lines the inside of the heart
• Myocardium: The middle and thickest layer of the heart
• Epicardium: The thin layer on the surface of the heart where the coronary arteries lay

The septa, or septum, are muscular walls that divide the heart into two sides.

The pericardium is a thin sac that contains the heart. It often is filled with fluid that helps separate the heart from other organs, including the lungs.

How the Heart Beats

Learn how the heart beats from Christopher L. Johnsrude, M.D., pediatric cardiologist and associate professor in the University of Louisville School of Medicine Department of Pediatrics. Dr. Johnsrude serves as director of the pediatric arrhythmia service at Norton Children’s Hospital.

How The Heart Beats

Heart Care at Norton Children’s Heart Institute

At the Norton Children’s Heart Institute, affiliated with the UofL School of Medicine, you will find a comprehensive array of advanced pediatric heart services and compassionate care for children of all ages, from before birth to newborns, kids and teens.

Our multidisciplinary team practices medicine with great skill. We use advanced diagnostic and surgical procedures to treat congenital heart defects and acquired heart conditions in children. We also provide lifelong follow-up care for adults with congenital heart disease. Our heart center truly provides care for a lifetime. From diagnosing a congenital heart defect before birth to caring for the adult needing follow-up later in life, we are your heart care partner for a lifetime.