How
does the heart function?
The heart is a powerful muscle slightly larger than your clenched
fist. It works as a pump to send oxygen-rich blood through all parts
of your body. Blood contains oxygen and nutrients that every cell
in your body needs to survive. The oxygen-rich blood travels throughout
the arteries and vessels, nourishing the body so that it can function
properly.
Your heart will beat an average of
100,000 times per day. In that time, it pumps more than 4,300 gallons
of blood throughout your entire body.
The
flow of blood
The heart is divided into two sides. Each side is divided again
into two chambers, the atrium (upper chamber) and ventricle
(lower chamber). Blood vessels (veins) carry blood to the heart
from the rest of the body. This blood carries carbon dioxide and
cellular waste products. The blood goes into the right atrium and
then to the right ventricle, where it is then pumped to the lungs
to dispose of wastes and receive a fresh oxygen supply. From the
lungs, the blood returns to the heart. It returns to the left atrium
and then to the left ventricle. The blood is then pumped out of
the heart by the left ventricle into the aorta. The left ventricle
is the chamber of the heart that is responsible for pumping blood
to all parts of the body. The aorta sends this blood to small arteries,
which carry the oxygen-rich blood to the rest of the body.
Coronary
arteries
The right and left coronary arteries branch off the aorta and then
divide into smaller branches, supplying all portions of the heart
with blood and oxygen. In order for the heart to function properly,
it must receive a continuous supply of fresh oxygen-enriched blood.
The coronary arteries surround the heart and carry the blood which
nourishes the heart muscle. The right coronary artery supplies blood
to the right and back sides of the heart. The left coronary artery
divides into two main branches--the circumflex and the left anterior
descending--supplying blood to the left side of the heart.
Heart
valves
There are four heart valves. They are all one-way valves to keep
blood moving through the various chambers of the heart.
The mitral valve guards the
opening between the atrium and the ventricle in the left side
of the heart. It allows blood to flow forward from the atrium
to the ventricle, and prevents blood from flowing backwards. The
mitral valve has tiny cords attached to the walls of the ventricles.
This helps support the valve’s small flaps or leaflets.
The aortic valve, also called
a semi-lunar valve, has three segments that prevent the return
of the blood from the aorta to the left ventricle. It looks like
three half Ping-Pong balls. Valves on the heart’s left side need
to withstand much pressure. Sometimes they wear out and leak or
become thick and stiff.
The pulmonary valve is located
at the junction of the pulmonary artery and the right ventricle.
When the right ventricle contracts, the pulmonary valve opens,
forcing the blood into the artery which leads to the lungs. It
is also a semi-lunar valve. When the chamber relaxes, this valve
closes and prevents a backflow of the blood.
The tricuspid valve is located
between the upper and lower chamber in the right side of the heart.
Its position corresponds to the mitral valve in the left side
of the heart.
