BLOOD SUPPLY

The heart, like all tissues in the body, requires oxygen to function

Indeed, it is the only muscle in the body that never rests

Thus, the heart has reserved for itself its own blood supply

This blood flows to the heart muscle through a group of arteries that begins less than onehalf inch from where the aorta begins

These are known as the coronary arteries, the first branch to come off the aorta they are two, the right and left coronary artery

These arteries deliver oxygen to both the heart muscle and the nerves of the heart

Both ventricles receive their blood supply from branches of the right and left coronary arteries

Each atrium, in contrast, receives blood only from a small branch of the corresponding coronary artery

The most abundant blood supply goes to the myocardium of the left ventricle, since the left ventricle does the most work and so needs the most oxygen and nutrients delivered to it

Anastomoses exist between the large branches of coronary arteries

These provide detours in which arterial blood can travel if the main route becomes obstructed i.e. they provide collateral circulation to a part

This phenomenon is important in cases of coronary artery diseases; when the interruption of coronary blood flow lasts only a few minutes, the symptoms are called angina, and there is no permanent damage to the heart

When the interruption lasts longer, that part of the heart muscle dies

This is referred to as a heart attack (myocardial infarction)

Most of the venous drainage of the heart is through the coronary sinuses which open into the right atrium

The remainder passes directly into heart chambers through the little venous channels.