Video Transcript
Which of the major blood vessels carry blood from the heart to the lungs or the body?
Did you know the average human has around five liters of blood in their body? We need this blood to be moving around our body constantly to make sure all our cells and tissues are supplied with the oxygen and nutrients they need and to help remove waste products. In the human body, there are three major classes of blood vessels: arteries, veins, and capillaries. Let’s have a look at the features of each in turn.
Arteries are generally the largest of the three blood vessels. Blood is pumped out of the heart at a relatively high pressure. Because they have to carry blood at this high pressure, arteries have very thick muscular walls. Arteries carry blood away from the heart. An easy way to remember this is that “artery” and “away” both start with the letter “a.” When blood is carried away from the heart, it is delivered to the other organs of the body, like the lungs.
Veins have a large lumen, which is the space in which the blood flows. They carry blood which is at a much lower pressure than in the arteries. Because of this, veins often contain valves to stop the blood flowing in the wrong direction. Veins are responsible for bringing blood from the lungs or the rest of the body back to the heart. You can remember this because veins include the word “in,” as they transport blood into the heart.
Capillaries are very small blood vessels. Unlike veins and arteries, capillary walls are only one cell thick. This is because the main job of capillaries is to supply cells, tissues, and organs with oxygen and nutrients and remove their waste products. Being only one cell thick allows substances to diffuse easily across the capillary wall and into the bloodstream or from the bloodstream into the surrounding cells.
Let’s look back at our question. Which blood vessel carries blood from the heart to the lungs or the body? We can see that one type of blood vessel carries blood away from the heart to the other organs. The correct answer is arteries.