Normal heart

Aorta (to body)

Pulmonary artery (to lungs)

Pulmonary veins (from lungs)

Left ventricle

Septum

Right atrium

Right ventricle

Inferior vena
cava

Unoxygenated blood from body tissues enters the right side of the heart and is pumped out to the lungs to pick up oxygen. Oxygenated blood from the lungs enters the left side of the heart and is pumped back to the body tissues.

Listen to the heartbeat:

Unoxygenated
blood (blue)

Oxygenated
blood (red)

Innocent murmurs

Still's murmur
Made when the left ventricle contracts, forcing blood into the aorta.

Listen to the murmur:

Ductus arteriosus
This blood vessel closes soon after birth. It normally disappears after the first day.

Structural murmurs

Atrial septal defect
A small hole between the two atria; often won't make a detectable sound until adolescence.

Ventricular septal defect
A hole in the muscle that separates the two ventricles; often closes as the child matures.

SOURCES: American Heart Association, University of Washington Department of Medicine, staff reports.