Heart Anatomy
Simply click on a region of the heart on the diagrams or the
hyperlinks listed below to learn more about the structures of the
heart.
Because the heart is composed primarily of cardiac muscle tissue that
continuously contracts and relaxes, it must have a constant supply of
oxygen and nutrients. The coronary arteries are the network of blood
vessels that carry oxygen- and nutrient-rich blood to the cardiac muscle
tissue.
The blood leaving the left ventricle exits through the aorta, the
body’s main artery. Two coronary arteries, referred to as the
"left" and "right" coronary arteries, emerge from the beginning of the
aorta, near the top of the heart.
The initial segment of the left coronary artery is called the left
main coronary. This blood vessel is approximately the width of a soda
straw and is less than an inch long. It branches into two slightly
smaller arteries: the left anterior descending coronary artery and the
left circumflex coronary artery. The left anterior descending coronary
artery is embedded in the surface of the front side of the heart. The
left circumflex coronary artery circles around the left side of the
heart and is embedded in the surface of the back of the heart.
Just like branches on a tree, the coronary arteries branch into
progressively smaller vessels. The larger vessels travel along the
surface of the heart; however, the smaller branches penetrate the heart
muscle. The smallest branches, called capillaries, are so narrow that
the red blood cells must travel in single file. In the capillaries, the
red blood cells provide oxygen and nutrients to the cardiac muscle
tissue and bond with carbon dioxide and other metabolic waste products,
taking them away from the heart for disposal through the lungs, kidneys
and liver.
When cholesterol plaque accumulates to the point of blocking the flow
of blood through a coronary artery, the cardiac muscle tissue fed by the
coronary artery beyond the point of the blockage is deprived of oxygen
and nutrients. This area of cardiac muscle tissue ceases to function
properly. The condition when a coronary artery becomes blocked causing
damage to the cardiac muscle tissue it serves is called a myocardial
infarction or heart attack.
The superior vena cava is one of the two main veins bringing
de-oxygenated blood from the body to the heart. Veins from the head and
upper body feed into the superior vena cava, which empties into the
right atrium of the heart.
The inferior vena cava is one of the two main veins bringing
de-oxygenated blood from the body to the heart. Veins from the legs and
lower torso feed into the inferior vena cava, which empties into the
right atrium of the heart.
The aorta is the largest single blood vessel in the body. It is
approximately the diameter of your thumb. This vessel carries
oxygen-rich blood from the left ventricle to the various parts of the
body.
The pulmonary artery is the vessel transporting de-oxygenated blood
from the right ventricle to the lungs. A common misconception is that
all arteries carry oxygen-rich blood. It is more appropriate to classify
arteries as vessels carrying blood away from the heart.
The pulmonary vein is the vessel transporting oxygen-rich blood from
the lungs to the left atrium. A common misconception is that all veins
carry de-oxygenated blood. It is more appropriate to classify veins as
vessels carrying blood to the heart.
The right atrium receives de-oxygenated blood from the body through
the superior vena cava (head and upper body) and inferior vena cava
(legs and lower torso). The sinoatrial node sends an impulse that causes
the cardiac muscle tissue of the atrium to contract in a coordinated,
wave-like manner. The tricuspid valve, which separates the right atrium
from the right ventricle, opens to allow the de-oxygenated blood
collected in the right atrium to flow into the right ventricle.
The right ventricle receives de-oxygenated blood as the right atrium
contracts. The pulmonary valve leading into the pulmonary artery is
closed, allowing the ventricle to fill with blood. Once the ventricles
are full, they contract. As the right ventricle contracts, the tricuspid
valve closes and the pulmonary valve opens. The closure of the tricuspid
valve prevents blood from backing into the right atrium and the opening
of the pulmonary valve allows the blood to flow into the pulmonary
artery toward the lungs.
The left atrium receives oxygenated blood from the lungs through the
pulmonary vein. As the contraction triggered by the sinoatrial node
progresses through the atria, the blood passes through the mitral valve
into the left ventricle.
The left ventricle receives oxygenated blood as the left atrium
contracts. The blood passes through the mitral valve into the left
ventricle. The aortic valve leading into the aorta is closed,
allowing the ventricle to fill with blood. Once the ventricles are full,
they contract. As the left ventricle contracts, the mitral valve closes
and the aortic valve opens. The closure of the mitral valve prevents
blood from backing into the left atrium and the opening of the aortic
valve allows the blood to flow into the aorta and flow throughout the
body.
The papillary muscles attach to the lower portion of the interior
wall of the ventricles. They connect to the chordae tendineae,
which attach to the tricuspid valve in the right ventricle and
the mitral valve in the left ventricle. The contraction of the
papillary muscles opens these valves. When the papillary muscles
relax, the valves close.
The chordae tendineae are tendons linking the papillary muscles to
the tricuspid valve in the right ventricle and the mitral valve in the
left ventricle. As the papillary muscles contract and relax, the chordae
tendineae transmit the resulting increase and decrease in tension to the
respective valves, causing them to open and close. The chordae tendineae
are string-like in appearance and are sometimes referred to as "heart
strings."
The tricuspid valve separates the right atrium from the right
ventricle. It opens to allow the de-oxygenated blood collected in the
right atrium to flow into the right ventricle. It closes as the right
ventricle contracts, preventing blood from returning to the right
atrium; thereby, forcing it to exit through the pulmonary valve into
the pulmonary artery.
The mitral valve separates the left atrium from the left ventricle.
It opens to allow the oxygenated blood collected in the left atrium to
flow into the left ventricle. It closes as the left ventricle contracts,
preventing blood from returning to the left atrium; thereby, forcing it
to exit through the aortic valve into the aorta.
The pulmonary valve separates the right ventricle from the pulmonary
artery. As the ventricles contract, it opens to allow the de-oxygenated
blood collected in the right ventricle to flow to the lungs. It closes
as the ventricles relax, preventing blood from returning to the
heart.
The aortic valve separates the left ventricle from the aorta. As the
ventricles contract, it opens to allow the oxygenated blood collected in
the left ventricle to flow throughout the body. It closes as the
ventricles relax, preventing blood from returning to the heart.
Copyright © 2006 Cardiovascular Consultants, LLP
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