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The Cardiovascular System

diastole, as during this time the aorta contracts passively.

Superior Venae Cavae

The superior vena cava (SVC) is a large but short vein that carries de-oxygenated blood from the
upper half of the body to the heart's right atrium. It is formed by the left and right brachiocephalic veins
(also referred to as the innominate veins) which receive blood from the upper limbs and the head and
neck. The azygous vein (which receives blood from the ribcage) joins it just before it enters the right
atrium.

Inferior Venae Cavae

The inferior vena cava (or IVC) is a large vein that carries de-oxygenated blood from the lower
half of the body into the heart. It is formed by the left and right common iliac veins and transports
blood to the right atrium of the heart. It is posterior to the abdominal cavity, and runs along side of the
vertebral column on its right side.

Coronary Arteries

Heart showing the Coronary Arteries The coronary circulation consists of the blood vessels that
supply blood to, and remove blood from, the heart muscle itself. Although blood fills the chambers of
the heart, the muscle tissue of the heart, or myocardium, is so thick that it requires coronary blood
vessels to deliver blood deep into the myocardium. The vessels that supply blood high in oxygen to the
myocardium are known as coronary arteries. The vessels that remove the deoxygenated blood from the
heart muscle are known as cardiac veins. The coronary arteries that run on the surface of the heart are
called epicardial coronary arteries. These arteries, when healthy, are capable of auto regulation to
maintain coronary blood flow at levels appropriate to the needs of the heart muscle. These relatively
narrow vessels are commonly affected by atherosclerosis and can become blocked, causing angina or a
heart attack. The coronary arteries are classified as "end circulation", since they represent the only
source of blood supply to the myocardium: there is very little redundant blood supply, which is why
blockage of these vessels can be so critical. In general there are two main coronary arteries, the left and
right.

• Right coronary artery
• Left coronary artery

Both of these arteries originate from the beginning (root) of the aorta, immediately above the aortic
valve. As discussed below, the left coronary artery originates from the left aortic sinus, while the right
coronary artery originates from the right aortic sinus. Four percent of people have a third, the posterior
coronary artery. In rare cases, a patient will have one coronary artery that runs around the root of the
aorta.

Hepatic Veins

In human anatomy, the hepatic veins are the blood vessels that drain de-oxygenated blood from the

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