Heart & Blood Flow
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Your Heart
The heart is a muscle about the size of your fist that lies in the chest, behind
and slightly to the left of the breastbone, and between the lungs. It is a
remarkable organ that works hard 24 hours per day, pumping blood through a
60,000-mile network of vessels in the body.
Your heart is actually a double pump. The right side of the heart is made up of
the right atrium (upper chamber) and the right ventricle (lower chamber). The
right side receives blood that is low in oxygen from all the veins in the body,
and then it pumps that blood through the pulmonary artery to the lungs, where
it will become re-oxygenated.
The left side of the heart consists of the left atrium (upper chamber) and the
left ventricle (lower chamber). The left side of the heart receives this
oxygen-rich blood from the lungs, which it then pumps through the aorta (the
largest vessel in the body) to the body.
While blood is circulating through the body, it delivers oxygen and nutrients to
tissue through the arteries and picks up carbon dioxide through the veins. The
veins return the de-oxygenated blood to the right atrium, and the cycle begins
again. This cycle of contraction and relaxation happens some 70+ times a
minute, or about 104,000 times a day. Over the course of an average lifetime,
the heart can beat up to 2.5 billion times. This is an amazing amount of work
for such a small organ.
Coronary Circulation
If the heart pumps oxygen-rich blood out to feed the body, what feeds the heart
muscle itself? As blood circulates through the heart to go to the lungs or
body, some of the blood flows into a set of much smaller blood vessels that
provide blood flow directly to the muscle of the heart. These arteries surround
or crown the heart and get their name of coronary arteries. This separate
circulatory system (called coronary circulation) keeps the heart nourished and
oxygenated.
The two main branches off the aorta that nourish the heart are the right and
left main coronary arteries. Coronary artery disease affects the arteries of
this circulatory system and causes a decrease in blood flow to the heart
muscle, which may result in damage to the heart.
Coronary artery disease is associated with
heart attack.
Heart Valves
The heart has four valves that function like one-way doors to keep blood in the
heart flowing in one direction. The valves are made up of two or three strong
little flaps of tissue called leaflets. These leaflets open to allow blood to
flow through the valve, and they close to prevent blood from flowing back into
the chamber from which it just came. The opening and closing of the valves is
controlled by blood pressure changes within each heart chamber.
The mitral valve is positioned in the heart's left side, between the left upper
chamber (left atrium) and the left lower chamber (left ventricle). The
tricuspid valve is positioned in the heart's right side, between the heart's
right upper chamber (right atrium) and the right lower chamber (right
ventricle). The pulmonic valve separates the right ventricle from the pulmonary
artery (which carries blood to the lungs). The aortic valve separates the left
ventricle from the aorta (which carries blood to the body).
Heart Disease
The heart valves can be affected by disease to the point that blood flow through
the heart is compromised, resulting in mild to severe symptoms. With the
advanced medical technology of today, these valves can be repaired (heart
valve repair) or replaced (heart
valve replacement). For more information on these types of diseases, go
to Heart Valve
Disease.
Adequate flow of healthy blood also is compromised when plaque (cholesterol and
other substances) builds up in the coronary arteries.
Coronary artery disease is the number one cause of
heart attack.
Additionally, the heart's electrical system, which is responsible for each heart
beat or contraction, can be affected by disease. The SA node, the AV node, or
other areas of the electrical system can malfunction. A disruption in these
areas can result in abnormal heartbeats from very slow heart rates (bradyarrhythmias),
to very fast heart rates (tachyarrhythmias),
to very irregular heart rates. For further information on these conditions and
how they are treated, go to the Learn More About section,
Normal Rhythm & Arrhythmias.
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