Microvilli: Definition & Function

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  • 0:01 What Are Microvilli?
  • 1:07 Where Are They Found?
  • 1:46 Why Are They So Important?
  • 3:22 Lesson Summary
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Lesson Transcript
Jeremy Battista
Expert Contributor
Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

There are many small structures that help cells and organs work properly. One of these structures are the microvilli. Learn about what these tiny structures do, and find out where they are located.

What Are Microvilli?

Microvilli, in the most simplistic terms, are tiny little projections that exist in, on, and around cells. They can exist on their own or in conjunction with villi. The linings in some mucous membranes, most specifically of the small intestine, there exist tiny folds that project out like numerous fingers. These are called villi. On each of the villi, there are even smaller folds that stick out like fingers called microvilli. If you have ever seen a metric ruler, you can see the centimeters and in between those are the millimeters. It is a similar thing here; the villi would be like the centimeters, while the microvilli would be the millimeters falling in between.

The microvilli have their own plasma membrane that covers them. Inside of them, they have almost no organelles, but they do have cytoplasm (cellular fluid) and some microfilaments (strands of actin, a protein), which help give them their structure. They are essentially bundles of cross-linked actin fibers. Think of them as the fibers of a cotton shirt.

Where Are They Found?

Microvilli are most often found in the small intestine, on the surface of egg cells, as well as on white blood cells. In the intestine, they work in conjunction with villi to absorb more nutrients and more material because they expand the surface area of the intestine. As you will see in a second, they are very important to us because of this fact.

They also play a role in egg cells as they help in anchoring the sperm to the egg, thus allowing for easier fertilization. In white blood cells, the microvilli again act as an anchoring point. They allow the white blood cell that is hurtling through the body to grab and stick to whatever it is going after at the given moment.

Why Are They So Important?

Microvilli are extremely important because they increase the surface area of the cell that they are found on. By having these tiny little folds in the membrane of whatever cell we are looking at, you get more out of the same package. Imagine for a second having a string that was six feet long, laid out on the floor. It takes up six feet of real estate just stretched out. Now if you make small bends in the string from end to end, you can shorten the amount of space that is taken significantly. You could probably even get that string to fit into a space only one foot long or less. I mean, look at those survival bracelets!

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Additional Activities

Modeling Microvilli

In this activity students will be creating a model of microvilli that demonstrate the importance of microvilli in the small intestine. To do this activity you will need paper towels, water, and a baking tray.

Expected Results

Based on the lesson, the folds in the paper towel will act like microvilli, increasing the surface area of the paper towel. This will allow the folded paper towels to absorb more than the flat paper towels, demonstrating how microvilli help the small intestine absorb nutrients.


Now that you understand the importance of microvilli in the body, we're going to make a model to demonstrate their usefulness in action. Models are important because they allow scientists to study things that are too large, too small or otherwise inaccessible in the lab. Since microvilli are deep inside our body, a model is a good choice to study their function. Follow the steps below to create your microvilli model and then answer the questions.

  1. Start by getting a roll of paper towels. Take one paper towel from the roll, cut it in half, and lay it flat. Next, loosely fold several paper towels accordion style until you have a rectangle the same size as the cut paper towel (when you look at it from the top), but 1" thick with folds.
  2. Now, pour one cup of water into a baking tray or dish.
  3. Use the first cut paper towel to soak up as much water as you can. Then measure the amount of water remaining in the pan. Subtract the amount of water remaining from the total you started with (1 cup) to get the amount of water absorbed. Record your results in the table below.
  4. Make sure there is no water left in the baking tray or dish, and then add 1 cup of fresh water.
  5. Repeat step 3 with the folded paper towels.

Paper TowelAmount of Water RemainingAmount of Water Absorbed


  1. Which paper towel represented the microvilli? How did you know?
  2. Which paper towel was able to absorb more water and why?
  3. How does this model relate to the microvilli in the small intestine?

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