Cilia vs Microvilli
Both cilia and microvilli are the projections of the plasma membrane, and they are found only in certain cells. These components have specific functions and most of them are found on the apical surface of epithelial cells. Cilia are considered as a fundamental component of eukaryotic cells and are absent in prokaryotes.
Long hair- like projections of the plasma membrane with cores made up of microtubules are known as cilia. Normally, the length of a cilium is around 5 to 10 µm and the diameter is about 0.2 µm. These structures are motile and can beat toward one direction so that they can move the entangle particles from the surface. Also, cilia can be found in some specialized cells like the sensory cells of a vertebrate ear as conventional cilia surrounded by actin-based stereocilia, which are responsible to provide initial sensory input for hearing.
The core of the cilium is made up of microtubules that are arranged uniformly in longitudinal orientation, known as, (9+2) orientation. 9+2 means that the core of each cilium contains nine microtubules doublets located peripherally and two single microtubules in the center. Each cilium originates directly from a special structure called basal body. Basal body has a different arrangement of microtubules. Instead of peripherally arranged nice microtubules in a cilium core, the basal body has nine microtubule triplets and has no central microtubules.
Microvilli are the minute finger- like elongated projections of the plasma membrane which exhibit a core of thin microfilaments. These microfilaments are held together to form bundles by cross-linking proteins known as villin and fimbrin. The main function of the microvilli is the absorption of certain substances. Cells produce microvilli, mainly, to increase the surface area for absorption (intestine surface), to transport absorbed materials, and to participate in the digestion of carbohydrates.
In general, the length of a microvillus is about 0.5 to 1.0 µm and the diameter is about 0.1 µm. Microvilli are packed in large numbers and make the surfaces called brush boarders. These brush boarders are present on the luminal surfaces of many epithelia like intestine, specialized for absorption.
What is the difference between Cilia and Microvilli?
• Cilia are longer than microvilli.
• Cilia have a wider diameter than microvilli does.
• The core of microvilli is made up of microfilaments while that of cilia is made up of microtubules, arranged in a (9+2) pattern.
• Microvilli are non-mortile whereas cilia are motile components.
• Cilia are used to move the cell bodies and other sweeping processes, whereas microvilli are used in the absorption process.
• Microvilli are located on the surfaces of the columnar epithelial cells of the small intestine and kidney tubule. In contrast, cilia are located on the surfaces of the columnar epithelia cells of the respiratory tract and uterine tube.
• Unlike microvilli, cilia extend slightly into the cell and are anchored via a special structure called basal body, which is made of microtubules.