# Microvilli: Definition, Structure, Functions and Location

> Microvilli are cell-surface projections that increase absorptive area. Explore their structure, functions, locations, and differences from villi and cilia.

Canonical URL: https://biologynotesonline.com/microvilli/
Author: Sourav Pan
Last updated: September 29, 2026

![Microvilli: Definition, Structure, Functions and Location](https://biologynotesonline.com/wp-content/uploads/2024/08/Location-of-Microvilli-in-Intestinal-and-Kidney-Epithelial-Cells.webp)

Microvilli are microscopic projections of the plasma membrane, covered by membrane and supported internally by actin. These extend from the surface of certain cells. A single projection is called a microvillus. The main function of microvilli is to increase the available surface area of the cell membrane. It is specially useful in absorptive epithelial cells, where more apical membrane surface is needed for absorption and exchange. They do not absorb every nutrient as separate independent structures. The parent epithelial cell performs the absorptive function, and microvilli provide more membrane area for this process.

Intestinal microvilli are present densely on the apical cell surface of intestinal absorptive epithelial cells, called enterocytes. Many such small projections remain packed together and form the brush border. This brush border faces the intestinal lumen and gives a large membrane surface to the enterocyte. Microvilli are the projections of individual cells. They are not same as [intestinal villi](https://biologynotesonline.com/human-digestive-system-organs-structure-functions/), because intestinal villi are much larger multicellular tissue projections of the intestinal mucosa.

## Location of Microvilli

- Microvilli are mostly present on the free or apical surface of some cells. They are not usually present all around the cell in same amount.

- They are common on epithelial cells where absorption and secretion takes place. The apical side faces the lumen or outer space, so microvilli remain exposed to that side.

- In the small intestine, microvilli are present on the apical surface of [enterocytes](https://biologynotesonline.com/physiology-of-digestion-organs-mechanism-regulation-functions/). These cells line the intestinal villi. The densely arranged microvilli form the brush border.

- They are also present in the large intestine, but the main absorptive brush border is more prominent in the small intestine. Here the microvilli remain towards the intestinal lumen.

- In kidney, microvilli are found on the luminal surface of [proximal tubule epithelial cells](https://biologynotesonline.com/nephron-definition-structure-physiology-functions/). These microvilli form a thick brush border. The border faces the filtrate inside the tubule.

- Microvilli may also be seen on epithelial cells of gall bladder. The apical surface of these cells has small projections which help in increasing the membrane surface.

- Some microvilli are present on cells of reproductive tract and other epithelial linings also. Their number and arrangement is not same in every tissue.

- In many locations, microvilli occur as scattered small projections. In enterocytes and proximal tubule cells, they are packed very densely and form a visible brush border under microscope.

- Microvilli are cellular projections. So their location is always on individual cells, not as a separate tissue layer like villi of the intestine.

![Microvilli on the apical surfaces of intestinal enterocytes and kidney proximal tubular epithelial cells, forming brush borders that face their respective lumens.](https://biologynotesonline.com/wp-content/uploads/2024/08/Location-of-Microvilli-in-Intestinal-and-Kidney-Epithelial-Cells-1024x725.webp)Microvilli on the apical surfaces of intestinal enterocytes and kidney proximal tubular epithelial cells, forming brush borders that face their respective lumens.

## Structure of Microvilli

A single microvillus is made up of the following structural components-

![Cutaway of a microvillus showing its plasma membrane, parallel actin filaments, bundling proteins, membrane linkages, rootlets, glycocalyx, and terminal web.](https://biologynotesonline.com/wp-content/uploads/2024/08/Microvillus-Structure-Showing-the-Actin-Core-and-Terminal-Web-819x1024.webp)Cutaway of a microvillus showing its plasma membrane, parallel actin filaments, bundling proteins, membrane linkages, rootlets, glycocalyx, and terminal web.

- [Plasma membrane](https://biologynotesonline.com/cell-membrane-plasma-membrane-structures-and-functions/) covering- Microvilli are covered by the plasma membrane of the same cell. The membrane goes up over each small projection and forms the outer boundary of the microvillus.

- Actin core- The central part of each microvillus contains a bundle of [actin filaments](https://biologynotesonline.com/microfilaments/). These filaments run lengthwise from the tip of the microvillus towards the cytoplasm. It gives support and keeps the microvillus in its narrow finger-like shape.

- Bundling proteins- The actin filaments are packed closely with the help of actin-binding proteins such as villin and fimbrin. These proteins hold the actin filaments together. Because of this, the core remains stiff and organised.

- Membrane and actin attachment- The actin bundle is attached to the surrounding membrane by side linking proteins. Myosin I and calmodulin take part in this attachment. This linkage keeps the membrane covering connected with the inner actin core.

- Rootlet region- At the base, actin filaments of microvilli extend down into the apical cytoplasm as rootlets. These rootlets do not stop suddenly at the membrane base. They enter into the supporting region below the microvilli.

- Terminal web- The rootlets are anchored in a network of cytoskeletal proteins called the terminal web. It is present just below the apical surface of epithelial cells. The terminal web stabilizes the microvilli and holds them in proper position.

- Brush border arrangement- In absorptive epithelial cells, many microvilli are placed very close to each other on the apical cell surface. This packed arrangement forms the brush border. In enterocytes, the brush border looks like a dense apical margin under microscope.

- [Glycocalyx](https://biologynotesonline.com/cell-coat/)- The outer surface of intestinal microvilli is covered by a carbohydrate-rich coat called glycocalyx. It is present outside the plasma membrane. In intestinal cells, some digestive enzymes and surface molecules are associated with this covering.

- General size and shape- Microvilli are short, slender and cylindrical cell projections. They are much smaller than intestinal villi. A villus is a multicellular tissue projection, but a microvillus is only the projection of one cell.

## How Microvilli Support Nutrient Absorption

Microvilli support the [absorption of nutrients](https://biologynotesonline.com/mechanical-and-chemical-digestion-of-food-absorptions-of-differenet-molecules/) in the small intestine through the following steps-

![Intestinal brush-border diagram showing lactose digestion, glucose and galactose uptake through SGLT1, fructose uptake through GLUT5, peptide uptake through PEPT1, and basolateral nutrient transport.](https://biologynotesonline.com/wp-content/uploads/2024/08/Intestinal-Microvilli-and-the-Mechanism-of-Nutrient-Absorption-725x1024.webp)Intestinal brush-border diagram showing lactose digestion, glucose and galactose uptake through SGLT1, fructose uptake through GLUT5, peptide uptake through PEPT1, and basolateral nutrient transport.

- In the small intestine, the apical surface of each enterocyte is covered with large number of microvilli. These small projections increase the membrane surface of the cell. A larger area is made available for digestive enzymes and transport proteins.

- The partially digested food comes near the brush border. Here, the brush border is the densely packed microvillar surface of the enterocyte. Carbohydrates are present mostly as disaccharides and smaller sugars, and proteins are present as small peptides.

- Digestive enzymes are present on the microvillar membrane. Disaccharidases such as lactase hydrolyse disaccharides into monosaccharides. Lactose is broken down into glucose and galactose. Peptidases, such as aminopeptidase N, hydrolyse peptides from their N-terminal end. So final digestion occurs very close to the microvilli surface.

- The digested products then reach the transporters present in same apical membrane. Glucose and galactose enter through sodium-glucose cotransporter 1 (SGLT1). The entry of glucose is linked with the entry of Na+. Fructose enters through glucose transporter 5 (GLUT5). Di- and tripeptides enter through peptide transporter 1 (PEPT1).

- Some di- and tripeptides are absorbed directly without complete breakdown outside the cell. A part of these peptides enter into the enterocyte in peptide form.

- Inside the enterocyte, the remaining peptides are hydrolysed by cytosolic peptidases. Free amino acids are formed inside the cell.

- In the last step, monosaccharides and amino acids leave through the basolateral membrane. Glucose crosses this membrane mainly through glucose transporter 2 (GLUT2). From the interstitial fluid, the absorbed nutrients are passed into the blood capillaries.

## Functions of Microvilli

Some of the important functions of microvilli are as follows-

- The primary function is to increase the available surface area of the cell membrane. A larger membrane area makes the cell more efficient in nutrient absorption, which is seen in the intestinal enterocytes and in the cells of the kidney proximal tubule.

- The microvillar membrane of the intestine carries digestive enzymes, which complete the final breakdown of nutrients before uptake.

- Microvilli also enlarge the secretory surface of the cell.

- The intestinal brush border works as a protective barrier. It keeps the resident microbiota and the pathogens of the gastrointestinal tract away from the enterocytes. In addition, the microvillar membrane is displaced towards the tip and is shed off as vesicles. These vesicles are enriched with intestinal alkaline phosphatase (IAP) and contribute to the mucosal barrier function.

- In the kidney proximal tubule, the microvilli act as mechanosensors. They sense the fluid drag force generated by the tubular flow and pass it on to the cytoskeleton at the terminal web.

- On immune cells, the microvilli are flexible and dynamic structures. The T cell microvilli help in antigen sensing, adhesion and signal transduction. They carry clusters of the [T cell receptor (TCR)](https://biologynotesonline.com/t-cell-t-lymphocyte/) and work as signalling hubs for the immune response.

- Arrays of microvilli are also found in photoreceptor cells, where they absorb the light entering the eye. In insects, this photoreceptive structure is called the rhabdomere.

## Microvilli vs Villi

The following are the differences between microvilli and villi-

![Magnification sequence showing a multicellular intestinal villus containing blood capillaries and a lacteal, an individual enterocyte, and microvilli projecting from its apical membrane.](https://biologynotesonline.com/wp-content/uploads/2024/08/Microvilli-vs-Villi-Structural-Differences-in-the-Small-Intestine-1024x683.png)Magnification sequence showing a multicellular intestinal villus containing blood capillaries and a lacteal, an individual enterocyte, and microvilli projecting from its apical membrane.

BasisMicrovilliVilliBasic natureMicrovilli are very small projections of the plasma membrane of a single epithelial cell. They are actin-based membrane protrusions.Villi are larger finger-like projections of the intestinal mucosa. These are tissue projections, not single cell projections.Structural levelThey are cellular structures. A microvillus belongs to one cell only.They are multicellular structures. A villus contains many epithelial cells and inner connective tissue core.SizeMicrovilli are much smaller and can be seen clearly under electron microscope. The apical surface covered with many microvilli is called brush border.Villi are comparatively larger and can be seen in light microscopic sections of small intestine. They project into the intestinal lumen.LocationThey are present on the apical surface of absorptive epithelial cells, mainly on enterocytes of intestine and proximal tubule cells of kidney.Villi are present in the small intestine. They form projections from the intestinal mucosal surface.CompositionEach microvillus has a membrane covering and internal actin filament bundle. It is held with cytoskeletal support.Each villus is lined by epithelial enterocytes and contains lamina propria, blood capillaries, lacteal and smooth muscle fibres.ArrangementMany microvilli remain densely packed on the apical surface and form the brush border.Many villi are arranged over the inner surface of the small intestine. They give a velvety appearance to the mucosa.Main functionTheir main function is to increase the apical membrane surface area of the cell. This gives more space for transporters and digestive enzymes.Their main function is to increase the absorptive surface of the intestinal wall and bring nutrients close to blood and lymph vessels.Relation with brush borderBrush border is made by the close packing of microvilli on the surface of enterocytes.Villi are covered by epithelial cells, and these epithelial cells have microvilli on their apical surface.ExampleMicrovilli occur on intestinal enterocytes as the brush border. They also occur in kidney proximal tubule cells.Villi are seen in the small intestine, especially on the mucosal lining of jejunum and ileum.

## Microvilli vs Cilia

The following are the differences between microvilli and [cilia](https://biologynotesonline.com/cilia-definition-structure-types-function/)-

![Comparison of an actin-supported microvillus and a microtubule-supported motile cilium, with cross-sections showing actin filaments and the typical 9+2 ciliary axoneme.](https://biologynotesonline.com/wp-content/uploads/2024/08/Microvilli-vs-Cilia-Differences-in-Internal-Structure-1024x683.webp)Comparison of an actin-supported microvillus and a microtubule-supported motile cilium, with cross-sections showing actin filaments and the typical 9+2 ciliary axoneme.

BasisMicrovilliCiliaBasic natureMicrovilli are small finger-like projections of the plasma membrane. These are mostly found on absorptive cells.Cilia are hair-like projections present on the cell surface. They are membrane-bound structures with internal cytoskeletal support.Structural supportThe core of microvilli is made up of actin filaments. These actin bundles keep the projection straight and narrow.Cilia have a microtubule based core called axoneme. In motile cilia, the axoneme usually has 9+2 arrangement.Main functionTheir main function is to increase the surface area of the cell membrane. This helps mostly in absorption.Motile cilia help in movement of fluid or materials over the cell surface. Primary cilia mainly act in sensing and signalling.MovementMicrovilli are generally non-motile. They do not beat.Some cilia are motile and show beating movement. Some are non-motile, like primary cilia.Position on cellMicrovilli occur on the apical surface of epithelial cells. In intestine, many microvilli form the brush border.Cilia also project from the cell surface, but they are not brush border structures. They may occur singly as primary cilium or many in ciliated epithelium.Basal attachmentMicrovilli are attached with the terminal web at their base. The actin rootlets pass down into this supporting region.Cilia arise from a basal body. The basal body is related to centriole structure and gives origin to the axoneme.ExamplesThey are seen on intestinal enterocytes and kidney proximal tubule cells. These cells need more membrane surface for absorption or reabsorption.Motile cilia are present in respiratory epithelium and help in moving mucus. Primary cilia are present in many vertebrate cells and work as sensory structures.Size and numberMicrovilli are shorter and usually very numerous on absorptive cells. They give a dense apical border.Cilia are usually longer than microvilli. They may be single or present in large number depending on the cell type.Relation with enzymesIn intestinal cells, microvilli carry digestive enzymes on the brush border surface. Final digestion occurs near this region.Cilia are not mainly enzyme-bearing absorptive surfaces. Their work is more related with movement or sensory signalling.General role in epitheliumMicrovilli make the epithelial surface more absorptive. The surface area is increased without making a separate tissue projection.Cilia make the epithelial surface active in movement or sensing. In motile ciliated cells, the beating helps to move substances along the epithelial surface.

## Microvilli at a Glance

BasisQuick summaryDefinitionMicrovilli are microscopic projections of the plasma membrane present on the surface of some cells.Singular formA single projection is called a microvillus.Main structural supportEach microvillus has an internal bundle of actin filaments. It keeps the projection narrow and supported.Main functionIt increases the surface area of the cell membrane. This is the major function.Common locationThey are mostly present on the apical surface of absorptive epithelial cells.Important exampleIn small intestine, enterocytes have many microvilli on their apical surface.Brush borderDensely packed microvilli together form the brush border. It is seen clearly in intestinal enterocytes and kidney proximal tubule cells.Role in intestineThey help in nutrient absorption by giving more membrane area for enzymes and transporters.Role in digestionSome digestive enzymes are present on the brush border surface. Final digestion of some carbohydrates and peptides occurs near this region.Role in kidneyIn kidney proximal tubule cells, microvilli help in reabsorption from the filtrate.MotilityMicrovilli are generally non-motile. They do not beat like cilia.Difference from villiMicrovilli are projections of a single cell. Villi are large multicellular tissue projections of the intestine.Difference from ciliaMicrovilli have actin filaments and mainly increase surface area. Cilia have microtubules and may help in movement or sensing.Exam pointMicrovilli = actin-based, non-motile, plasma membrane projections that increase surface area for absorption.

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