Blood: Function & Components

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  • 0:01 Blood
  • 0:50 Components
  • 2:10 Functions
  • 3:47 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.

You know your heart pumps blood through your blood vessels, but do you know why this is important? Learn why your blood must keep moving, as well as the things that make it up, like plasma, red blood cells, white blood cells and platelets.


I'm sure you know from experience that if you cut yourself deep enough, you'll bleed. And you probably learned in school that your heart pumps blood through your blood vessels. But did you know that your body has up to a gallon and a half of that red stuff? And that if you stretched out all of your blood vessels in one line, it would cover more than 60,000 miles?

Keeping your blood inside those blood vessels keeps you alive. Without it, parts of your body could not communicate with each other, you couldn't get warm in the winter or cool off in the summer, and you couldn't fight off infections. There's more to blood than you might have thought, so let's take a closer look at what this somewhat thick liquid does for you and what it's made of.


Blood is always moving through you. In fact, you can feel it moving under your skin by feeling your pulse. Every pulse you feel is blood squirting through the artery. The part of your blood that allows it to flow is called plasma. This is a watery fluid that carries nutrients and other substances.

Floating in the plasma are three types of cells. You have red blood cells that carry oxygen to your body cells. This is important because all cells in your body depend on oxygen to function properly. An interesting fact is that the more oxygen your blood has, the brighter red it will be. This is why blood that just passed through your lungs is a brighter red than blood found in vessels farther away.

Floating in the plasma, you will also find white blood cells that fight infections and help your immune system. Think of a white cell as the White Knight from a fairy tale that comes in to save the day.

The remaining cells are more like pieces of cells. We call them platelets, and they help your blood to clot, which means they help stop bleeding. When you get a cut, you actually cut a blood vessel. When this happens, platelets get called to the scene to help patch the wound.


The constant flow of blood allows it to carry out its main function, which is transportation. You might want to think of your blood as your body's highway. Every minute of every day, your blood is picking up substances your cells need, like oxygen and nutrients. At the same time, your blood is dropping off things that are no longer needed, like carbon dioxide and other wastes so they can find their way out of your body.

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