Epithelial Cells: Difference between revisions
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An epithelium can be defined as a ‘sheet’ of [[Cells|cells]] coating the external surface of a structure or covering a cavity. Epithelial cells are what make up this cellular layer | An epithelium can be defined as a ‘sheet’ of [[Cells|cells]] coating the external surface of a structure or covering a cavity. Epithelial cells are what make up this cellular layer, often used to seperate body tissue from the external environment it's found in: | ||
#[[Skin|Skin]] | #[[Skin|Skin]] | ||
#Intestine | #[[Intestine|Intestine]] | ||
#[[Lungs|Lungs]] | #[[Lungs|Lungs]] | ||
#[[Kidney|Kidney]]<br> | #[[Kidney|Kidney]]<br> | ||
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=== Classification<br> === | === Classification<br> === | ||
An epithelial tissue can be made of one | An epithelial tissue can be made up of one or more layers of [[Cells|cells]], which are classified as ''simple'' or ''stratified''. The epithelial cells can be categorised further with regards to their shape: flat, which are known as ''squamous;'' roughly cubed, or ''cuboidal''; and finally the taller ones are known as ''columnar''. <ref>Fry, M. Page, E. (2008) Catch up Biology, 3rd Edition, Banbury: Scion Publishing Ltd.</ref><br> | ||
=== Properties & Structure<br> === | === Properties & Structure<br> === | ||
There are two sides to an epithelial cell, the [[Apical membrane|apical membrane]] is | There are two sides to an epithelial cell, the [[Apical membrane|apical membrane]] which is usually exposed to the extracellular fluid in the [[Lumen|lumen]] and the [[Basolateral membrane|basal membrane]] which is secured to another cell.<br> | ||
[[Cilia|Cilia]] are often found on the [[Apical membrane| | [[Cilia|Cilia]] are often found on the [[Apical membrane|apical membrane]] and these significantly increase surface area to aid absorption, and even in some organs are used as a brush boarder to prevent infection. | ||
In a layer of epithelia there are junctions between each cell known as '[[Tight junction|tight]]' or '[[Leaky junctions|leaky]]' junctions. The tight junctions limit small [[Molecules|molecules]] or [[Ions|ions]] moving laterally, creating and upholding membrane domains.<br> | In a layer of epithelia there are junctions between each cell known as '[[Tight junction|tight]]' or '[[Leaky junctions|leaky]]' junctions. The tight junctions limit small [[Molecules|molecules]] or [[Ions|ions]] moving laterally, creating and upholding membrane domains.<br> | ||
=== References === | === References === | ||
<references /> | <references /> | ||
Revision as of 16:18, 15 October 2014
An epithelium can be defined as a ‘sheet’ of cells coating the external surface of a structure or covering a cavity. Epithelial cells are what make up this cellular layer, often used to seperate body tissue from the external environment it's found in:
Classification
An epithelial tissue can be made up of one or more layers of cells, which are classified as simple or stratified. The epithelial cells can be categorised further with regards to their shape: flat, which are known as squamous; roughly cubed, or cuboidal; and finally the taller ones are known as columnar. [1]
Properties & Structure
There are two sides to an epithelial cell, the apical membrane which is usually exposed to the extracellular fluid in the lumen and the basal membrane which is secured to another cell.
Cilia are often found on the apical membrane and these significantly increase surface area to aid absorption, and even in some organs are used as a brush boarder to prevent infection.
In a layer of epithelia there are junctions between each cell known as 'tight' or 'leaky' junctions. The tight junctions limit small molecules or ions moving laterally, creating and upholding membrane domains.
References
- ↑ Fry, M. Page, E. (2008) Catch up Biology, 3rd Edition, Banbury: Scion Publishing Ltd.