Blood Vessels: Arteries, Capillaries & More

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  • 0:01 Blood Vessels
  • 0:23 Arteries and Arterioles
  • 1:51 Capillaries
  • 2:33 Veins and Venules
  • 4:21 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

In this lesson, you will take a trip around the circulatory system and encounter the various blood vessels, including arteries, veins, and capillaries. Come along as we follow the path to every cell of your body.

Blood Vessels

Blood flows through blood vessels, which form the closed system called the circulatory system. Like a system of roads, the circulatory system has its highways, back roads, and alleyways, which we call arteries, veins, and capillaries. In this lesson, we will learn about blood vessels and how they transport blood throughout the body.

Arteries and Arterioles

Diagram of blood vessel types
Blood Vessel Types

Each time your heart beats, blood is forced into large arteries. Arteries are blood vessels that carry blood away from the heart to other tissues. An easy way to jog your memory when thinking about arteries is to remember that arteries carry blood away from the heart. Because arteries are the first vessels that the heart pumps blood through, they experience the highest blood pressure, so they have thick elastic walls to withstand the high pressures. These large arteries expand when the pressure of the blood rises and then recoil when the heart relaxes between beats to provide a smooth flow of blood through your body.

From the large arteries, blood starts its one-way journey around the body, moving into smaller and smaller arteries and then into arterioles. Small arteries, such as arterioles, are less elastic and have more smooth muscle than the larger arteries. These smaller, muscular arteries do not expand as much when blood enters them and therefore provide the greatest resistance to blood flow through the arterial system, which helps regulate your blood pressure.

The miles of arteries and arterioles in your body are simply transportation vessels and can be thought of as the highways and back roads of your circulatory system.


Microscopic capillaries extend into all body tissues.
Capillary Beds

Only the microscopic capillaries serve as the location for the exchange of gases and nutrients between blood and tissue cells. The capillary walls are very thin and composed of a single layer of endothelial cells, which are very thin flattened cells that line the inner walls of all of the blood vessels. Capillaries are the alleyways that extend and branch into every tissue of your body, ensuring that every cell has a blood supply. It is here, in the capillary beds, that your cells pick up oxygen and nutrients and drop off carbon dioxide and wastes.

Veins and Venules

The blood is now ready for its return trip to the heart through more transportation vessels. After leaving the capillary beds, blood starts its trip back to the heart by first entering venules, which are groups of capillaries that unite to become small vessels that drain the capillary beds. These small vessels in turn empty into larger vessels called veins. Veins are blood vessels that carry blood toward the heart from various tissues. Veins are far from the initial pressure of the heartbeat and therefore under low pressure. Their walls are thinner than those of the corresponding arteries, and their inner diameter tends to be larger.

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