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Microvilli (singular form: microvillus) are tiny hair-like strands attached to the cell membrane.  Under a microscope, they look kind of like the little hairs on a toothbrush.  They help increase the surface area of cells to help them take in and let go molecules. Because of this, they are not found in plant cells, which have cell walls that keep their rigid shape and prevent surface area expansion.
 Illustration of microvilli on cell membrane

Microvilli Function in Small Intestine

Microvilli don’t appear on all cells. Rather, they are only found in specialized cells, like the villi in the small intestine and white blood cells.
Villi in the small intestine help us digest the food we eat. They are big strands, more like “fingers” than “hair”, and are made up of many cells. Villi make it easy for nutrients to move from the small intestine to our bloodstream. Microvilli are part of villi cells and help increase the surface area of the small intestine. Without them, the small intestine’s surface area would be 600 times smaller!
In the small intestine, microvilli also help with the intake of nutrients from our food. Microvilli contain enzymes that help break down big molecules into smaller parts. The enzymes in microvilli help turn chunky carbohydrates and proteins into nice amino acids and molecules. These are smaller and can easily pass through the villi into our bloodstream.
Here’s a helpful YouTube video! It will help to better explain how villi and microvilli work in the small intestine!

Altogether, there are thousands and thousands of microvilli in the small intestine. There are so many of them, in fact, that they form what is called the “brush border”. The brush border got its name because old microscopes weren’t strong enough to see individual microvilli. Instead, what scientists first saw on the surface of the small intestine was a large, fuzzy fringe. Hence, they named this cellular structure the “brush border”!
3d illustration of microvilli on white blood cells

White blood cells with microvilli on the cell membrane

Microvilli Function in White Blood Cells

Microvilli also exist on the surface of white blood cells. White blood cells are part of our immune system and act like bodyguards. If a dangerous bacteria or virus enters the body, white blood cells move to take down the threat. Because of this, white blood cells need to move quickly through the bloodstream. Microvilli are important because they help white blood cells migrate around the body!

Written by: Minh Nguyen