Granulocytes: Types and Functions

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  • 0:25 White Blood Cells and…
  • 2:26 Neutrophils,…
  • 3:56 Eosinophils and Basophils
  • 5:07 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

In this lesson, you will learn what a leukocyte, granulocyte, neutrophil, eosinophil, and basophil are. You'll also learn about the importance of phagocytosis and chemotaxis.

A Knight in Shining Armor

There's a cliché about a knight in shining armor on a white horse coming to save a princess, town, or even country in need. Your body also has its own set of knights in shining armor, all on white horses, all ready to defend you when you are in need!

White Blood Cells and Granulocytes

In your body, the white horses carrying the knights in shining armor are called leukocytes, which is the more technical term for a white blood cell.

Some of the white horses have round spots on them. These horses are called granulocytes, and they are leukocytes of the innate immune system that have granules in their cytoplasm.

To simplify that definition, imagine again that our white horse holding up the knight in shining armor is our white blood cell. Well, now imagine that the body of that horse has a bunch of black circles, like a Dalmatian. Those would be the granules, or little balloons, chock full of molecules that serve several general functions.

First, they can act like the gastric juice of a horse. If the white blood cell were to eat something, like an invading bacteria, those granules would help kill and digest the bacteria inside of its cytoplasm.

Other types of granules, for example those containing a compound called histamine, can be released out of the cell in order to vasodilate, or expand the size of blood vessels during inflammation, in order to increase blood flow to a certain area. The increased blood flow will bring additional leukocytes and other cells and molecules to help fight off an infection. Or, granules can be released to kill a cell outright by causing it to burst open.

Finally, these granules can also be used to signal cells to come to a certain area to help kill an invader. It's kind of like when a horse neighs to get the attention of other horses. These white horses, our granulocytes, release these granules out of their cytoplasm to get the attention of other white blood cells so they can help kill an invader.

Neutrophils, Phagocytosis, and Chemotaxis

In any case, there are three sub-species, so to speak, of granulocytes, or spotted white horses, in your body.

The first is called a neutrophil. These are granulocytes involved in fighting off pathogens, such as bacteria and fungi, and are the most abundant leukocyte in mammals. These are the cells that are responsible for that icky yellowish pus you may see seeping out of infected wounds. Furthermore, I know you know that horses love to eat hay. Well, these horses also love to eat as well. The process of engulfing a pathogen in order to neutralize or destroy a pathogen is called phagocytosis.

The way that neutrophils and other white blood cells find their source of food, such as a bacteria they need to eat and destroy, is through something called chemotaxis. This is a process whereby a cell finds its way to a target by way of chemical signals.

To put that into perspective, you know that horses have really big and soft noses. Well, in order to find their food source, the hay, they use their big nose to smell little particles in the air, which guide the horse in the direction of the food source. Likewise, leukocytes use little chemicals released by foreign invaders or those of your own body in order to hone in on the place where they need to go in order to find and kill their prey.

Eosinophils and Basophils

Last, but certainly not least, we have two more spotted white horses, our granulocytes, to go over.

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