Anatomy
and Function of the Heart Valves
The
heart consists of four chambers, two atria (upper
chambers) and two ventricles (lower chambers).
There is a valve through which blood passes before
leaving each chamber of the heart. The valves
prevent the backward flow of blood. These valves
are actual flaps that are located on each end
of the two ventricles (lower chambers of the heart).
They act as one-way inlets of blood on one side
of a ventricle and one-way outlets of blood on
the other side of a ventricle. Normal valves have
three flaps, except the mitral valve, which has
two flaps. The four heart valves include the following:
- tricuspid valve: located
between the right atrium and the right ventricle
- pulmonary valve: located
between the right ventricle and the pulmonary
artery
- mitral valve: located
between the left atrium and the left ventricle
- aortic valve: located
between the left ventricle and the aorta
As the
heart muscle contracts and relaxes, the valves
open and shut, letting blood flow into the ventricles
and atria at alternate times. The following is
a step-by-step illustration of how the valves
function normally in the left ventricle:
- After the left ventricle
contracts, the aortic valve closes and the mitral
valve opens, to allow blood to flow from the
left atrium into the left ventricle.
- As the left atrium
contracts, more blood flows into the left ventricle.
- When the left ventricle
contracts again, the mitral valve closes and
the aortic valve opens, so blood flows into
the aorta.
Heart
valves can have one of two malfunctions:
- regurgitation
The valve(s) does not close completely, causing
the blood to flow backward instead of forward
through the valve.
- stenosis
The valve(s) opening becomes narrowed or does
not form properly, inhibiting the flow of blood
out of the ventricle or atria. The heart is
forced to pump blood with increased force in
order to move blood through the stiff (stenotic)
valve(s).
Heart
valves can have both malfunctions at the same
time (regurgitation and stenosis). When heart
valves fail to open and close properly, the implications
for the heart can be serious, possibly hampering
the heart's ability to pump blood adequately
through the body. Heart valve problems are one
cause of heart failure.
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