How the Heart Works
The heart is a muscle about the size of your fist.
The heart works like a pump and beats about 100,000 times a day.
A healthy adult heart generally beats 60 to 100
times a minute, but it can beat faster or slower at times. For example,
physical activity, strong emotion, certain medicines, fever, or infection can
make the heart beat faster. A persons heart rate generally slows down
during sleep. Some very fit athletes always have heart rates below 60 beats a
minute because their hearts work so well.
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 vessels that carry blood
away from the heart to the body.
Illustration of a
Healthy Heart Cross-Section
Heart Chambers
The heart has four chambers or
roomstwo on the left side of the heart and two on the
right.
- The atria 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 (PULL-mun-ary) valve is in the
right side of the heart, between the right ventricle and the entrance to the
pulmonary artery that carries blood to the lungs.
- The mitral (MI-tral) 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 hearts valves open and close, they
make a lub-DUB sound that a doctor can hear using a
stethoscope.
- The first soundthe lubis
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 soundthe DUBis
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 hearts electrical system works. |