Heart Anatomy

This is the external appearance of a normal heart.
The epicardial surface is smooth and glistening.
The amount of epicardial fat is usual.
The left anterior descending coronary artery extends
down from the aortic root to the apex.

From the moment it begins beating until the
moment it stops, the human heart works tirelessly.
In an average lifetime, the heart beats more than
two and a half billion times, without ever
pausing to rest. Like a pumping machine,
the heart provides the power needed for life!!

1.Right Coranary 9.Right Atrium
2.Left Anterior Descending 10.Right Ventricle
3.Left Circumflex 11.Left Atrium
4.Superior Vena Cava 12.Left Ventricle
5.Inferior Vena Cava 13.Papillary Muscles
6.Aorta 14.Chordae Tendineae
7.Pulmonary Artery 15.Tricuspid Valve
8.Pulmonary Vein 16.Mitral Valve
Aortic Valve(not pictured) 17.Pulmonary Valve

The heart you see drawn on the average Valentine
is only a rough representation of the actual
structure of the heart. Your heart is
actually shaped more like an upside-down pear.

The human heart is primarily a shell. There
are four cavities, or open spaces,
inside the heart that fill with blood.
Two of these cavities are called atria.
The other two are called ventricles.
The two atria form the curved top
of the heart. The ventricles meet at the
bottom of the heart to form a pointed
base which points toward the left side
of your chest. The left ventricle contracts
most forcefully, so you can best feel
your heart pumping on the left side
of your chest.

The left side of the heart houses one
atrium and one ventricle. The right side
of the heart houses the others. A wall,
called the septum, separates the right and
left sides of the heart. A valve
connects each atrium to the ventricle below it.
The mitral valve connects the left atrium
with the left ventricle. The tricuspid valve
connects the right atrium with the right ventricle.

The top of the heart connects to a few
large blood vessels. The largest of these
is the aorta, or main artery, which
carries nutrient-rich blood away from the heart.
Another important vessel is the pulmonary artery
which connects the heart with the lungs
as part of the pulmonary circulation system.
The two largest veins that carry blood
into the heart are the superior vena
cava and the inferior vena cava. They
are called "vena cava" because they are
the "heart's veins." The superior is located
near the top of the heart.
The inferior is located beneath the superior.

The heart's structure makes it an efficient,
never-ceasing pump. From the moment of
development through the moment of death,
the heart pumps. The heart, therefore,
has to be strong. The average heart's
muscle, called cardiac muscle, contracts and
relaxes about 70 to 80 times per minute
without you ever having to think about it.
As the cardiac muscle contracts it pushes
blood through the chambers and into the vessels.
Nerves connected to the heart regulate the speed
with which the muscle contracts. When you run,
your heart pumps more quickly. When you
sleep, your heart pumps more slowly.

Considering how much work it has to do,
the heart is surprisingly small. The
average adult heart is about the size of
a clenched fist and weighs about 11
ounces (310 grams). Located in the middle
of the chest behind the breastbone, between
the lungs, the heart rests in a
moistened chamber called the pericardial cavity which
is surrounded by the ribcage. The diaphragm,
a tough layer of muscle, lies below.
As a result, the heart is well protected.

Function of the Heart

Every cell in your body needs oxygen in order
to live and function. The role
of the heart is to deliver the
oxygen-rich blood to every cell in the body.
The arteries are the passageways through which
the blood is delivered. The largest
artery is the aorta, which branches off the
heart and then divides into many smaller arteries.
The veins carry the deoxygenated blood
back to the lungs to pick up more oxygen,
and then back to the heart once
again. Blood flows continuously through the
circulatory system, and the heart muscle is
the pump which makes it all possible!

Coronary Arteries

Your heart, just like all other muscles
in the body, needs its own supply of
oxygen in order to function properly. Although
its chambers contain blood, the heart receives no
nourishment from the blood inside the chambers.
The heart gets its blood supply from the
coronary arteries. The two major coronary
arteries (the right coronary artery and the
left main coronary artery) branch off the aorta,
and then divide into many smaller arteries
that lie in the heart muscle and feed the heart.

For further information contact:

National Heart Lung, and Blood Institute (NHLBI)
Information Center
P.O. Box 30105
Bethesda MD 20824-0105

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