There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from the capillaries back toward the heart.


Arteries carry blood away from the heart. The largest is the aorta. The circulation to all the body except the lungs is called the systemic circulation and carries oxygenated blood. The circulation to the lungs is called the pulmonary circulation and carries deoxygenated blood.

Arteries divide into smaller arterioles which divide again and again and eventually become capillaries.

Arteries have thick muscular walls, which enable them to resist the pressure of blood flow. The innermost wall is a single layer of cells and provides a smooth lining which allows the least possible frictional resistance to the flow of blood. The middle layer is made up of elastic tissue which can stretch when the heart beats. The outer layer is in the form of a thin covering.

Pressure within arteries is maintained by elastic stretch and recoil, the recoil keeping up a continuous pressure in the artery, which keeps the blood flowing evenly.


Veins are large blood vessels which carry blood back to the heart. Systemic veins carry deoxygenated blood. The largest veins are the superior and inferior vena cava, which return blood to the heart from the upper body and lower body respectively. Veins have a system of valves to prevent back-flow.

The flow of blood is aided by the action of muscles, especially the large muscles of the leg. Like the artery the vein has a single cell layer, as its lining.

Unlike the artery the vein has a poorly developed middle layer. This is because the vein is not working under pressure and does not stretch in the same way as the artery. Unlike the artery the vein has a thick outer layer. It needs this for strength, as it does not have muscle in its walls. The inside of the vein is much larger than in an artery, reflecting the slower rate of blood flow.


Capillaries are the smallest blood vessels. The average diameter is eight micrometers with a very thin wall of 0.2 micrometers. The body has approximately 100,000 km. of capillaries. They are the site for exchange of gases, nutrients and waste between circulation and body tissues.

At the Alpha Vein Clinic Las Vegas we take a look at all three of these main groups to make an accurate and thorough diagnosis. We appreciate being able to help our patients solve their vein and leg problems. Call us today so we can help you at  (702) 430 7661.

Alpha Vein Clinic


3150 N. Tenaya Way Ste. 400

Las Vegas, NV, 89128

(702) 430 7661

Dr. Sassan Kaveh

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