How the Heart Works
To understand tetralogy of Fallot, it's helpful to
know how a healthy heart works.
Your child's heart is a muscle about the size of his
or her fist. The heart works like a pump and beats 100,000 times a day.
The heart has two sides, separated by an inner wall
called the septum. The right side of the heart pumps blood to the lungs to pick
up oxygen. Then, oxygen-rich blood returns from the lungs to the left side of
the heart, and the left side pumps it to the body.
The heart has four chambers and four valves and is
connected to various blood vessels. Veins are the blood vessels that carry
blood from the body to the heart. Arteries are the blood vessels that carry
blood away from the heart to the body.
A Healthy Heart Cross-Section
![Illustration: Cross-Section of a Healthy Heart and its inside structures.](https://webarchive.library.unt.edu/eot2008/20080920163209im_/http://www.nhlbi.nih.gov/health/dci/images/heart_interior.gif)
The illustration shows a
cross-section of a healthy heart and its inside structures. The blue arrow
shows the direction in which oxygen-poor blood flows from the body to the
lungs. The red arrow shows the direction in which oxygen-rich blood flows from
the lungs to the rest of the body.
Heart Chambers
The heart has four chambers or "rooms."
- The atria (AY-tree-uh) are the two upper chambers
that collect blood as it comes into the heart.
- The ventricles are the two lower chambers that
pump blood out of the heart to the lungs or other parts of the body.
Heart Valves
Four valves control the flow of blood from the atria
to the ventricles and from the ventricles into the two large arteries connected
to the heart.
- The tricuspid (tri-CUSS-pid) valve is in the
right side of the heart, between the right atrium and the right ventricle.
- The pulmonary valve is in the right side of the
heart, between the right ventricle and the entrance to the pulmonary artery,
which carries blood to the lungs.
- The mitral (MI-trul) valve is in the left side of
the heart, between the left atrium and the left ventricle.
- The aortic (ay-OR-tik) valve is in the left side
of the heart, between the left ventricle and the entrance to the aorta, the
artery that carries blood to the body.
Valves are like doors that open and close. They open
to allow blood to flow through to the next chamber or to one of the arteries,
and then they shut to keep blood from flowing backward.
When the heart's valves open and close, they make a
"lub-DUB" sound that a doctor can hear using a stethoscope.
- The first sound—the
“lub”—is made by the mitral and tricuspid valves closing at
the beginning of systole (SIS-toe-lee). Systole is when the ventricles
contract, or squeeze, and pump blood out of the heart.
- The second sound—the
“DUB”—is made by the aortic and pulmonary valves closing at
beginning of diastole (di-AS-toe-lee). Diastole is when the ventricles relax
and fill with blood pumped into them by the atria.
Arteries
The arteries are major blood vessels connected to
your heart.
- The pulmonary artery carries blood pumped from
the right side of the heart to the lungs to pick up a fresh supply of oxygen.
- The aorta is the main artery that carries
oxygen-rich blood pumped from the left side of the heart out to the body.
The coronary arteries are the other important
arteries attached to the heart. They carry oxygen-rich blood from the aorta to
the heart muscle, which must have its own blood supply to function.
Veins
The veins are also major blood vessels connected to
your heart.
- The pulmonary veins carry oxygen-rich blood from
the lungs to the left side of the heart so it can be pumped out to the body.
- The vena cava is a large vein that carries
oxygen-poor blood from the body back to the heart.
For more information on how a healthy heart works,
see the Diseases and Conditions Index article on
How
the Heart Works. This article contains animations that show how your heart
pumps blood and how your heart's electrical system works. |