The Arterial Tree

The arterial system is responsible for the transport of oxygenated blood from the heart to all the cells, tissues, and organs of the body. As the large artery (the aorta) leaves the heart, it curves to the left, forming an arch. The main blood vessels to the neck, head, and arms emanate from the arch of the aorta. The aorta then courses downward behind the heart and in front of the spine. As it descends, it issues numerous branches to the chest and to the organs of the abdomen. Finally, as it reaches the pelvis, the aorta divides into two large branches (bifurcation of the aorta), each large branch supplying one of the lower extremities. Secondary and tertiary smaller arteries are called arterioles. Eventually, within the substance of the tissues and organs, the arterioles become threadlike, forming the arterial side of the capillary system.

Arterial Blood Flow to and from the Heart

We have already discussed the flow of arterial blood from the heart. Of equal importance is the supply of arterial blood to the heart. The heart receives its supply of oxygenated blood from the lungs by way of the pulmonary veins. These important vessels deliver their cargo to the left atrium and thence to the left ventricle by way of the mitral or bicuspid valve, which lies between the left atrium and the left ventricle. Disease of the mitral valve may interfere with this process and have serious effects on the heart and circulation. 

The Base of the Aorta

The aortic valve is a three-cusped valve at the entrance to the aorta. The cusps open with left ventricular systole, or contraction, allowing the strong surge of blood to flow from the ventricle into the aorta. The first vessels off the aorta are the right and left coronary arteries which supply the heart muscle itself. During diastole, when the heart is relaxing and refilling with blood, the aortic valve closes. The three cusps from a secure barrier, preventing the backflow of blood from the aorta into the left ventricle at a time when the pressure in the aorta is actually higher than the residual pressure in the ventricle. A damaged aortic valve may allow aortic regurgitation, or backflow of blood from the aorta into the left ventricle, causing potentially serious heart and circulatory damage.