Cilia
Cilium (plu: cilia) is an organelle that is short and filament-like. It looks like an eyelash that protrudes from eukaryotic cells, and can be motile or non-motile. Motile cilia help in movement and locomotion, such as in Protozoans. Primary cilia are nonmotile, they are used to sense external cues such as light and odour. Additionally, it also senses internal fluid flow and other growth factors.
Cilia is a microtubule based cylindrical-structure that is composed of a central core called axoneme. The core is composed of two central microtubules that are surrounded by nine pairs of outer microtubules. The outer layer of the microtubule is surrounded by a membrane that is continuous with the cell membrane.
The cilia beat in unison to move the mammalian ova through the oviducts. It helps carry food through the digestive system of snails, circulates cerebrospinal fluid in animals and swipes off debris from the respiratory tracts of mammals.
Stereocilia
Stereocilia are non-motile apical modifications of cells. They are composed of parallel actin filaments (cross linked with fibrin) that are bound by a plasma membrane. They are finger-like projections that are sometimes branched. They are cylindrical, long structures that have the same characteristics as a cell membrane.
Stereocilia can be seen in vas deferens, sensory cells of the ear and epididymis. They lack axoneme and may or may not be covered by a glycocalyx coating.
Microvilli
Microvilli are protrusions that look like bristles. They are present as protrusions on cellular membranes that help in increasing the surface area for diffusion. Additionally, it helps in absorption, cellular adhesion and secretion. Structurally the microvilli are made of cross linked actin filaments that are covered by a plasma membrane.
The microvilli can be seen on the surface of small intestines forming a brush border, on the plasma surface of eggs, and around sperms in clusters. In the egg, it helps in anchoring the sperm cells, and by forming clusters around the sperm cells, it allows easy fusion of the egg and sperm.
The microvilli are coated with glycocalyx. In the intestine, the presence of glycocalyx coated microvilli helps in nutrient digestion and absorption. It contains enzymes that help in digestion. If the layer is damaged, it can lead to diarrhoea or intestinal malfunction. A common example is lactose intolerance. Organisms that lack the enzyme lactase in their glycocalyx coating, cannot digest lactose from the dairy products.
Cilia vs. Stereocilia vs. Microvilli
| Cilia | Stereocilia | Microvilli |
| Description | ||
| 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. |
| Motility | ||
| Motile or non-motile | Non-motile | Non-motile |
| Glycocalyx Coating | ||
| Absent | May or may not be present. | Present |
| Core Structure | ||
| The core structure of cilia is made up of microtubules. | The core structure is made up of actin filaments. | The core structure is made up of actin filaments. |
| Ultrastructure | ||
| 9+2 | Absent | Absent |
| Location | ||
| Cilia can be seen on protozoans and respiratory epithelium cells. | Stereocilia are seen in vas deferens, sensory cells of the ears and epididymis. | It can be seen on the surface of small intestines, the surface of eggs and around sperm in clusters. |
| Functions | ||
| It helps in movement and locomotion. | Stereocilia increase the conductance of membranes by depolarising and hyperpolarising the cells. | It helps in nutrient absorption, digestion, secretion and cellular adhesion. |
Explore BYJU’S Biology for more related topics.
Also Read:
- Difference Between Cilia And Flagella – An Overview
- Why are villi present in the intestine and not in the stomach?
- How do we hear sound through the ear?
Frequently Asked Questions on the Difference between Cilia, Stereocilia and Microvilli
What are the structural differences and similarities between cilia and stereocilia?
The cilia are motile structures that are made up of microtubules, whereas stereocilia are non-motile structures that are made up of actin filaments.
What’s the difference between villi and microvilli?
Size of villi ranges between 0.5 to 1.6 mm while that of microvilli is about 1 µm in length. Additionally, villi are seen on the mucous membrane, specifically in the small intestine. Microvilli, on the other hand are small extension seen on the cell membrane of various structures.
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