We have already discussed various important cell organelles in a living cell but now we are going to discuss the structure and function of cilia which is frequently observed in different cells where movement is required.
Table of Contents
What is Cilia?
We will mainly focus on the structure and function of cilia but we need to know the basics about cilia and we will introduce you to the special structure found in eukaryotic cilia, what is cilia, different types of cilia, different disorders associated with cilia.
On the surface of some eukaryotic cells, fine hair-like structures are observed and they may be numerous in number or only one such structure can be present on the surface of the cell and this structure is known as cilia.
Some cells have to show different types of movement, sometimes some cells can move from one place to another place due to various reasons, and to move they need a structure that can create a propulsion force to move the cell and fine hair-like cilia help to move the cells and the organism or cell have cilia are known as ciliates.
Structure of Cilia:
In external appearance, cilia look like hair-like slender structures and emerge from the surface of the cell and can present in many numbers or may be present in a single.
An outer extension of the plasma membrane forms a sheath around the cilia and inside the plasma membrane covers the proteinaceous structure of the cilia present.
At the point from where the cilia originated, the plasma membrane has a microtubules structure known as the basal body and the basal body is made of nine peripheral triplet proteins.
The long cylindrical body of cilia is made of nine pairs of peripheral microtubules and in the center, two microtubules are present so the structure of cilia can be represented as (9 + 2) microtubular arrangement and this structure is also known as axoneme.
The outer peripheral nine pairs of microtubules are very flexible due to their dynein protein structure and it helps to move the cilia easily.
Function of Cilia:
In our nasal chamber when we inhale external air for oxygen than with air different types of material enter into our nasal passages and some of them are unwanted and some are harmful.
Different microbes, pollen grains, dust particles enter along with air through the nasal passages but the epithelial present on the nasal passages have cilia which help to move the unwanted or harmful substances in a certain direction to prevent their entry.
Always the cilia do not perform the movement, sometimes they act as sensory structure, and in that case, they are non-movable but help to sense some stimulation.
For example, some cell in the kidney have cilia and when the urine pass through then the cilia bend due to the flow of urine, and this trigger a stimulation which means urine is passing out one another example of non-motile cilia when the cilia act as a sensory structure is the cilia present on the retina.
Different Types of Cilia:
Motile Cilia:
This type of cilia is involved in different types of movement as seen in the epithelial cells of respiratory pathways. In the respiratory tract, the movable cilia help to move different types of particles that are not required for our body, and the mucus secreted by mucous cells is also removed by motile cilia present on the respiratory tract epithelium.
Non Motile Cilia:
Some cilia are non-motile and when we had not enough information about those non-motile cilia scientists thought that they may be vestigial cell organelles but when much research is done on them scientists find that they also perform some very important functions, most of them work as sensory cell antenna and it is most commonly observed in retina, kidney and most of the cases they receive mechanical stimulation.
Read More: Structure and Function of Centrioles
How Cilia Help Cell in Moving From One Place to Another Place?
In a living organism, most of the cells remain fixed in the tissue but some cells in a living organism need to show different types of movement and some of them move from one place to another place. The cilia show special movements which creates a propulsion force and enable the cells to move from one place to another.
What is the Function of Cilia Present on Our Nasal Chamber Lining?
We inhale and exhale through the nasal chamber and take oxygen from the air and exhale carbon dioxide into the air. When we inhale oxygen with air, different harmful dust particles present in the air also enter into our nasal chamber, if they reach the lungs then they can accumulate in the lungs. The cilia present on the epithelium of the nasal chamber prevent the entering of dust particles present in the air.
How Cilia Act As a Sensory Structure in our Body?
In some organs cilia help in other functions other than movement, in the retina, the cilia in the photosensitive areas take part in sensation. In some part of our urinary system cilia act as sensory structure, when urine flow through a specific part of the urinary system the cilia present on the tract bend and it stimulates the sensation of urge for urination.
What is Ciliates?
Some cells have a special hair-like fine structure on their surface which takes part in different types of function cell to cell, cilia. The organisms that have the cells with cilia are known as ciliates, cilia occur in different parts of our body, in the epithelium of the nasal chamber, on the retina, in the urinary tract.
What is Basal Body?
In those cells where cilia are present, cilia originate from a point on the surface of the cell and the base of the cilia occurs inside the cytoplasm. The structure from where the cilia extent throughout the plasma membrane and extend outside of the cell are known as the basal body.
What is Axoneme?
In some cells, hair-like slender cell organelle is present which is formed by a proteinaceous structure in which 9 pairs of microtubules are present on the periphery and 2 microtubules present in the center, this arrangement of microtubule is known as (9 + 2) microtubular arrangements and this structure is known as Axoneme.
Which Components Give Flexibility to Cilia?
Cilia show different types of movement and it is possible due to their flexibility but the flexibility comes in cilia due to its special structure. In cilia, nine peripheral microtubular structures give it a hollow structure and the dynein protein present on peripheral nine pairs of microtubules give it extra flexibility.
What is Motile Cilia and Their Functions?
Motile cilia are able to show different types of movements and this movement gives some cells in our body some special features. In our respiratory tract, epithelial tissue has cilia which help in removing the mucus and it is possible due to the ability to show different types of movements in cilia.
What are the Non-Motile Cilia and What are Their Functions?
All the cilia present in a living tissue may not be motile, some of them are non-motile, but they are not useless. Those non-living cilia also have some important functions, most of them receive sensory information, for example, cilia in the retina, cilia in the kidney act as sensory cell organelles.
In Which Organisms Cilia Are Locomotory Organ?
In the case of some protozoa and some other animals that locomote through cilia, they help the animal to swim in fluid medium at a very fast rate. It is a locomotory organ in smaller animals but in higher animals, they perform different types of functions like receiving sensory stimulus, movement of small particles.
Reference:
Structure and Function of Cilia
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