http://www.cardioconsult.com/Anatomy/
             

             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.
             

   
             

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

             Coronary Arteries
             
             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.


             
             Superior Vena Cava
             
             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.
             


             Inferior Vena Cava
             
             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.
             


             Aorta
             
             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.
             


             Pulmonary Artery
             
             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.
             


             Pulmonary Vein
             
             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.
             


             Right Atrium
             
             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.
             


             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.
             


             Left Atrium
             
             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.
             


             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.
             


             Papillary Muscles
             
             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.
             


             Chordae Tendineae
             
             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."
             


             Tricuspid Valve
             
             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.


             
             Mitral Value
             
             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.
           

 
             Pulmonary Valve
             
             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.


             
             Aortic Valve
             
             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.