In order to continue enjoying our site, we ask that you confirm your identity as a human. Thank you very much for your cooperation. Arteries are blood vessels responsible for carrying oxygen-rich blood away from the heart to the body. Veins are blood vessels that carry blood low in oxygen from the body back to the heart for reoxygenation. Arteries and veins are two of the body’s main type of blood vessels. These vessels are channels that distribute blood to the body. They’re part of two closed systems of tubes that begin and end at the heart. These systems of tubes are either:
There are three types of arteries. Each type is composed of three coats: outer, middle, and inner.
There are four types of veins:
Use this interactive 3-D diagram to explore an artery. Use this interactive 3-D diagram to explore a vein. The walls of veins and arteries are both made up of three layers:
Unlike arteries, veins contain valves. Veins need valves to keep the blood flowing toward the heart. Theses valves are particularly important in the legs and arms. They fight gravity to prevent the backflow of blood. Arteries don’t need valves because the pressure from the heart keeps the blood flowing through them in one direction. The cardiovascular system is a closed system of vessels called arteries, veins, and capillaries. They’re all connected to a muscular pump called the heart. The cardiovascular system keeps a continuous and controlled movement of blood that delivers nutrients and oxygen to every cell in the body. It does this through thousands of miles of capillaries between the arteries and the veins.
Nutrients and oxygen are delivered to every cell in your body through a circulatory system. The heart pumps oxygenated blood to your cells through arteries. It pumps oxygen-depleted blood away from your cells through veins.
Blood vessels may be tiny but they cover a lot of ground. The smallest blood vessels measure only five micrometers. To give you some perspective, a strand of human hair measures about 17 micrometers. But if you took all the blood vessels out of an average child and laid them out in one line, the line would stretch over 60,000 miles. An adult’s would be closer to 100,000 miles long. There are three kinds of blood vessels: arteries, veins, and capillaries. Each of these plays a very specific role in the circulation process. Arteries carry oxygenated blood away from the heart. They’re tough on the outside but they contain a smooth interior layer of epithelial cells that allows blood to flow easily. Arteries also contain a strong, muscular middle layer that helps pump blood through the body. Capillaries connect the arteries to veins. The arteries deliver the oxygen-rich blood to the capillaries, where the actual exchange of oxygen and carbon dioxide occurs. The capillaries then deliver the waste-rich blood to the veins for transport back to the lungs and heart. Veins carry the blood back to the heart. They’re similar to arteries but not as strong or as thick. Unlike arteries, veins contain valves that ensure blood flows in only one direction. (Arteries don’t require valves because pressure from the heart is so strong that blood is only able to flow in one direction.) Valves also help blood travel back to the heart against the force of gravity.
Skill: • Identification of blood vessels as arteries, capillaries or veins from the structure of their walls
Identification of Blood Vessels Blood vessels can be identified from histological slides or images according to the thickness of their walls:
Identify the Blood Vessel
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