Difference between Cilia, Stereocilia and Microvilli

The difference between cilia, stereocilia, and microvilli is slight and we can observe it by knowing their structure and the place where they exist. These are hair-like microscopic structures that exist in the human body. Cilia are made of microtubules, while stereocilia and microvilli are made of actin filaments. The shortest is microvilli, intermediate height will be the cilia and the tallest will be stereocilia. Moreover, if we compare the stereocilia with the cilia they don’t have any central mechanism for movement. They are immobile and they do not have any microtubules what they have is only microfilaments like actin filaments.

What is Cilia?

Cilia are the surface projections that are located in the apical area of the cells and have a basal body. They will go upward from the basal body and have some microtubule arrangement. The centriole mechanism is present for motility, and the microtubules are arranged in (9+2) form for bending movement.

They have the protein dynein and ATPase for dynamic activity which can help to bend the cilia and to move the fluid in the lumen which could be the respiratory tract like the paranasal sinuses, or the trachea, bronchi, or maybe it is the female reproductive system where the uterine tube or the oviduct will move the fertilized conceptus towards the uterus for implantation. These cilia are present in the nutrient tube during fertilization. In the fallopian tube, there are two types of cells: peg cells, which lack cilia, and simple columnar cells, that contain cilia.

What is Stereocilia?

The Stereocilia are found in the inner ear, to detect movement. The epidermis and the ductus difference in the male reproductive system don’t have cilia, they have stereocilia. Stereocilia are stationary and serve only to increase the surface area of absorption in the epidydmis and vas deferens.

Stereocilia are quite long compared with the finger-like projections of microvilli. Columnar cells, also known as principal cells, have stereocilia. Stereocilia, like microvilli, features an inner core of actin filaments, but the distinction between the two is their extraordinary length. The length of the stereocilia is nearly equivalent to the length of the nucleus of the main cells.

What is Microvilli?

Some cells have projections that resemble fingers; they are known as microvilli. The central canal in brain is filled with CSF and lined by appending epithelium. The columnar epithelium found in the central canal will be modified with microvilli and cilia. Microvilli are used to increase the surface area of absorption and modify the contents of the CSF. The cilia that border the CSF-filled ventricles, such as the central canal, will transport CSF from the brain ventricles to the central canal, showing that the ventricular lining is composed of both cilia and microvilli.

Microvilli that resemble the striated border of the small intestine, are found in the gastrointestinal tube. The regular arrangement of microvilli in the small intestine is shown by the striated border.

Difference between Cilia, Stereocilia, and Microvilli

The following table lists the difference between cilia, sterocilia, and microvilli:

Characteristics	Cilia	Stereocilia	Microvilli
Definition	These are tiny hair-like structures found on the surface of some cells.	These are the bundles of actin-filament.	Microvilli are folds of cell membranes of certain cells.
Location	Found in the respiratory tract.	Found on the cochlea in the inner ear, in some parts of male reproductive tract such as epididymis and vas deferens.	Found in locations where absorption and secretion take place, especially in the digestive tract and kidneys.
Motility	Some are mobile and some are immobile. Cilia are shorter than stereocilia. Contractile	Non-motile Stereocilia are longer than cilia. Non-contractile	Non-motile Microvilli are shorter than cilia. Non-contractile
Function	Move cells and propel objects. In the respiratory tract, cilia sweep out mucus, dust and other foreign matter.	Stereocilia in the inner ear aid in the hearing and balance while stereocilia in the male reproductive tract facilitate absorption.	Increase the surface area for absorption.
Ultra-Structure	9+2 structure	No	No
Cytoplasmic or protoplasmic	Cytoplasmic	Protoplasmic	Protoplasmic
Protein Fibers	Microtubules	Actin filaments	Actin filaments
Shape	Long-cylindrical process (uniform diameter from base to apex)	Conical shape	Brush Border Minute process

FAQs on Cilia, Stereocilia and Microvilli

Is Stereocilia a Microvilli?

Stereocilia (or stereovilli or villi) are non-motile apical cell modifications. They are distinct from cilia and microvilli, but are closely related to microvilli. They form single “finger-like” projections that may be branched, with normal cell membrane characteristics.

What is Stereocilia and Cilia?

Cilia are short, hair-like structures present on cell surfaces. Stereocilia are bundles of actin filaments that are sometimes branched. Microvilli are bristle-like protrusions found on cell surfaces.

Where are Stereocilia?

The tips of these stereocilia are embedded in a proteinaceous membrane, the tectorial membrane, which covers the hair cells and is attached medially along the apex of the cochlear duct.

What Proteins are in Stereocilia?

Their cores are composed of parallel actin filaments that are cross-linked and stabilized by several actin-binding proteins, including fascin-2, plastin-1, espin, and XIRP2.

Is Stereocilia a Cell?

In the inner ear, stereocilia are the mechanosensing organelles of hair cells, which respond to fluid motion in numerous types of animals for various functions, including hearing and balance.

Where is Cilia Located?

Motile cilia are found in the airways (lungs, respiratory tract and middle ear), the brain ventricles and fallopian tube and are highly structurally related to sperm tails.

Is Cilia in the Eye?

All three layers of the eyeball contain primary cilia, which play important roles in maintaining normal eye function.