Microvillus
Microvillus | |
---|---|
Details | |
Identifiers | |
Latin | microvillus |
MeSH | D008871 |
TH | H1.00.01.1.01011 |
FMA | 67296 |
Anatomical terms of microanatomy |
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Microvilli (sg.: microvillus) are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume,
Structure
Microvilli are covered in plasma membrane, which encloses
Each microvillus has a dense bundle of cross-linked
In the enterocyte microvillus, the structural core is attached to the plasma membrane along its length by lateral arms made of
The space between microvilli at a cell's surface is called the intermicrovillous space. Intermicrovillous space increases with contractile activity of myosin II and tropomyosin, and decreases when contraction ceases.
Locations
Thousands of microvilli form a structure called the
Microvilli are also of importance on the cell surface of
Relationship to cell
As mentioned, microvilli are formed as cell extensions from the plasma membrane surface.
Actin filaments, present in the cytosol, are most abundant near the cell surface. These filaments are thought to determine the shape and movement of the plasma membrane.
The nucleation of actin fibers occurs as a response to external stimuli, allowing a cell to alter its shape to suit a particular situation.
This could account for the uniformity of the microvilli, which are observed to be of equal length and diameter. This nucleation process occurs from the minus end, allowing rapid growth from the plus end.
Though the length and composition of microvilli is consistent within a certain group of homogenous cells, it can differ slightly in a different part of the same organism.
For example, the microvilli in the small and large intestines in mice are slightly different in length and amount of surface coat covering.[3]
Function
Microvilli function as the primary surface of nutrient absorption in the gastrointestinal tract. Because of this vital function, the microvillar membrane is packed with enzymes that aid in the breakdown of complex nutrients into simpler compounds that are more easily absorbed. For example, enzymes that digest carbohydrates called
Glycocalyx
The microvilli are covered with
This layer may be used to aid binding of substances needed for uptake, to adhere nutrients or as protection against harmful elements.
It can be another location for functional enzymes to be localized.
Clinical significance
Destruction
The destruction of microvilli can occur in certain diseases because of the rearrangement of cytoskeleton in host cell. This is seen in infections caused by EPEC subgroup Escherichia coli, in celiac disease, and microvillus inclusion disease[5] (an inherited disease characterized by defective microvilli and presence of cytoplasmic inclusions of the cell membrane other than the apical surface).
The destruction of microvilli can actually be beneficial sometimes, as in the case of elimination of microvilli on white blood cells which can be used to combat auto immune diseases.[6]
Congenital lack of microvilli in the intestinal tract causes
See also
References
- ISBN 978-1-58112-468-2. Retrieved 25 November 2010.
- ^ The Cytoskeleton: Cytoskeleton in specialized tissues and in pathological states, edited by JE Hesketh and IF Pryme, Elsevier, 1996ISBN 1559386894, 9781559386890. Vol3, pp371, M1[permanent dead link]
- PMID 34599101.
- ^ Malathy Kapali, MD, Ronald Jaffe, MD and Rocco M Agostini Jr. B.Sc. Final Diagnosis: Microvillus Inclusion Disease. "Final Diagnosis -- Case 163". Archived from the original on 1999-10-06. Retrieved 2006-02-19.
- ^ Shattuck, T. (2004) Cells studied for immune function. "Cells studied for immune function". Archived from the original on 2016-08-20. Retrieved 2006-02-19..
External links
- Anatomy photo: TermsCells&Tissues/structures/microvilli - Comparative Organology at University of California, Davis
- Histology image: 21904loa – Histology Learning System at Boston University - "Ultrastructure of the Cell: microvilli and basal enfoldings, endocytic vesicles"
- Histology image: 20601loa – Histology Learning System at Boston University - "Ultrastructure of the Cell: microvillous border and Junctional Complex, oblique section"