Question Video: Comparing Structures of the Three Main Types of Blood Vessels: Veins, Arteries, and Capillaries Biology

Complete the table to correctly compare the structure of the three major blood vessels.

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Video Transcript

Complete the table to correctly compare the structure of the three major blood vessels.

This question provides us with a partially filled-in table. We’re given the names of the three types of blood vessels along the top and various features of their structure along the side. And we’re being asked to fill in these four blank spaces with the correct information. In order to fill in these lengths, we’ll review what we know about the structure of the three major types of blood vessels. And we’ll start by reviewing their functions, since we know that structure and function are directly related.

Well, these are all types of blood vessels. So, we know that their primary function is to carry blood. The function of veins is to carry blood into the heart. We’re reminded of this because we can see the word “in” in the word vein. The function of the arteries is to carry blood away from the heart. And we’re reminded of this because both artery and away start with “a.” The function of the capillaries is to carry blood and allow the exchange of materials.

Here we have a diagram that represents the general route of blood flow through these three types of blood vessels. Blood from the heart pumps through the arteries, where eventually it branches off into a network of tiny blood vessels known as capillaries. Here, materials like oxygen, carbon dioxide, water, glucose, and many more pass into and out of the bloodstream. The capillaries connect and eventually join a vein, and the vein carries the blood back to the heart.

In order to answer our question, I’ve drawn more detailed diagrams of a vein, an artery, and a capillary. And the information we’re looking for in these diagrams is the size of the lumen or the space that the blood passes through, the width of the wall of the blood vessel, and whether or not the blood vessel possesses any valves which are special structures that keep blood flowing in one direction.

We’ll start by filling in the missing information for the vein column. We can see that the width of the wall is thin, and that part is already filled in. The size of the lumen compared to the other blood vessels is quite large. And we also can see that valves are present. Because of the size of the lumen of the vein and their relative distance from the heart, the blood pressure within them is quite low, which is why some veins possess valves, which keep the blood flowing in the correct direction and prevent it from flowing backwards.

Next, let’s work on the artery column. The size of the lumen is relatively small. And the blood pressure in arteries is higher than in veins, so they don’t need valves to keep blood flowing in one direction. Because of the high blood pressure, arteries also need thick, muscular walls that prevent them from being damaged.

Finally, let’s complete the capillary column. Capillaries have very thin walls, only one cell layer thick, which is what allows the easy exchange of materials into and out of the bloodstream. The size of the lumen is very small, so small in fact that blood cells pass through in single file. And there are no valves present in capillaries. The blood within them flows from the high pressure of the artery to the low pressure of the vein without the need for these special structures.

And now our table is complete. We filled in that arteries have thick walls, veins have a large lumen, and that valves are present in veins but not present in capillaries.

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