Cilia Structure

In eukaryotic cells, the Cilia structure is cylindrical protuberances that project from the larger cell body. Cilia are classified as motile (moving) or non-motile (stable). Those non-motile cilia that function as sensory organelles are also known as primary cilia. A cell’s primary cilium functions as the cell’s antenna and is found in most mammalian cell types. Olfactory neurons have several non-motile cilia, as do transient embryonic nodes, which have one motile cilium, termed nodal cilia, which is crucial in establishing the asymmetry between the right and left sides of the body.

Eukaryotic Cilia structure and flagella, or undulipodia, resemble each other structurally, though some distinction is made based on function or length. The immotile cilia, referred to as primary cilia, communicate with other cells or the environment.

Cilia structure

Axonemes are microtubule-based cytoskeletons that are found inside the Cilia structure and flagella. Primary cilium axonemes typically have nine microtubules, while motile cilia have two singlets of microtubules, plus the outer doublets (referred to as a 9+2 cilium). Intraflagellar transport (IFT) is a process in which proteins travel along the length of cilia thanks to transporters in the axoneme.

Inner and outer dynein arms on the axoneme move motile cilia. As part of this retrograde movement, IFT uses cytoskeletal dynein motor 2 to move back toward the cell body. Membranes contiguous with, but not identical to, the plasma membrane surround the cilium.

If a mother centriole is associated with a cilium, it is called the basal body, upon which the cilium rests. A mammal’s basal body comprises a barrel-shaped bundle of nine microtubules, three subdistal appendages and nine strut-like structures called distal appendages, which attach the barrel to the membrane at the base of cilia. As the ciliary axoneme extends, two of the triplet microtubules extend to become doublets. This is all about Cilia’s structure. 

Cilia Function

 A cell can move or be passed by other substances or objects. A Cilia structure is a cellular structure responsible for the movement of an entire organism and is found in some organisms called ciliates. It’s important to remember that cilia cover the surface of the unicellular protist Paramecium, which is capable of both moving and feeding. The cilia are also responsible for moving food into the organism’s mouth and covering the organism’s exterior.

Cilia can help remove contaminants from organs and tissues by moving fluids over cells. Nasopharynxes and tracheas are lined with cilia. Mucus, bacteria, and other debris are removed from the lungs by these ciliated epithelial cells during the respiratory process. Fallopian tubes have ciliated epithelial cells as well. As the egg moves towards the uterus, the cilia help in fertilisation.

An example of a kinocilium is found at the apex of hair cells in vertebrates. Associated with stereocilia are non-motile collections of actin filaments called mechanoreceptors.

Cilia Types

There are two different types of cilia.

Motile Cilia

These can be seen in a large number on the surface of a cell. A human’s respiratory epithelium is made up of these cells. In this place, they function to purge the lungs of mucus and dust.

Non-motile Cilia

It was discovered in 1898 that the primary cilia are non-motile. Until then, they were thought of as vestigial organelles. Research has recently revealed the biological role of primary cilia as a sensory cellular antenna that coordinates a wide range of cell signalling pathways. Apart from these, they also help in: Signaling the kidneys to produce urine properly. They serve as sensory receptors (mechanoreceptors). It helps transfer the particle from light-sensitive cells to the other in the retina.

Cilia Characteristics 

Cilia structure anatomy differs from that of other protists in several ways. Now let’s see what the characteristics of cilia are:

• Cilia:

Due to the presence of cilia, ciliated protozoans are known as ciliates. Cellular Cilia structure is hair-like projections or organelles that originate in the cytoplasm. Cilia facilitate the movement of an organism. Cilia enables the ciliates to sense changes in their environment and move from one place to another. They can then react appropriately to changing conditions. Almost the entire surface of the being is covered with cilia, which are short and numerous. While some organisms, such as Euplotes and Aspidistra, swim in water using their cilia, some, such as Paramecium, swim without cilia.

• Nuclei: 

There are two types of nuclei found in ciliates: macronucleus and micronucleus. The micronucleus is called a diploid nucleus because it contains two copies of each chromosome. The number of micronuclei in one cell can be large or small. Macronuclei are essentially short pieces of DNA. Micronuclei undergo mitosis during cell division, and macronuclei get divided into two.

• Oral vacuole: 

It is known as oral grooves that some ciliates, such as Paramecia, have a mouth-like structure to feed themselves. Food is transported through cilia to the food vacuole via the cytopharynx. This is where it breaks down. Ciliates absorb food and nutrients without an oral groove.

• Contractile Vacuole:

Ciliates use the contractile vacuole to drain the cell of excess water. As well as the anterior contractile vacuole, the paramecia contain posterior contractile vacuoles. The water in the cell moves to the contractile vacuole whenever its concentration is high. This process maintains both osmotic pressure and ionic balance. A high water level inside the cell may also cause the cells to burst. When this procedure is implemented, the cells will also not burst.

Conclusion

Ciliates are classified as parasitic or free-living. Free-living ciliates are found anywhere in the environment because they are not attached to a host. On the other hand, parasitic ciliates live entirely inside their hosts. Paramecium is a free-living ciliate that lives in freshwater bodies and feeds on bacteria. Balantidium coli is a parasitic ciliate that lives in human bodies as endoparasites and causes dysentery. In addition, soil contains other ciliates, such as Paraenchelys terricola and Apospathidium terricola. Ciliates of this type live in soil that has a high water level. The concentration of ciliates in the soil varies globally based on water, nutrients, and other factors.