Circular folds
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2008-04-24T12:27:44Z
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{{Infobox Anatomy |
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Latin = plicae circulares |
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GrayPage = 1173 |
Image = Gray1057.png |
Caption = Interior of the descending portion of the duodenum, showing bile papilla. |
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DorlandsPre = p_24 |
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}}
The '''circular folds''' ('''valves of Kerckring''') (also, '''plicae circulares''') are large [[valvular]] flaps projecting into the lumen of the [[bowel]].
==Composition==
They are composed of reduplications of the [[mucous membrane]], the two layers of the fold being bound together by submucous tissue; unlike the folds in the [[stomach]], they are permanent, and are not obliterated when the [[intestine]] is distended.
==Location==
The majority extend transversely around the cylinder of the intestine for about one-half or two-thirds of its circumference, but some form complete circles, and others have a spiral direction; the latter usually extend a little more than once around the bowel, but occasionally two or three times.
==Size==
The larger folds are about 8 mm. in depth at their broadest part; but the greater number are of smaller size.
The larger and smaller folds alternate with each other.
==Distribution==
They are not found at the commencement of the [[duodenum]], but begin to appear about 2.5 or 5 cm. beyond the [[pylorus]].
In the lower part of the descending portion, below the point where the [[bile duct|bile]] and [[pancreatic duct]]s enter the intestine, they are very large and closely approximated.
In the horizontal and ascending portions of the duodenum and upper half of the [[jejunum]] they are large and numerous, but from this point, down to the middle of the ileum, they diminish considerably in size.
In the lower part of the [[ileum]] they almost entirely disappear; hence the comparative thinness of this portion of the intestine, as compared with the duodenum and jejunum.
==Function==
The circular folds slow the passage of the [[food]] along the intestines, and afford an increased surface for [[absorption]]. They are covered with small fingerlike projections called [[intestinal villi|villi]] (singular, villus). Each villus, in turn, is covered with microvilli. The microvilli absorb fats and nutrients from the [[chyme]].
==External links==
* {{SUNYAnatomyLabs|39|12|03|02}} - "Intestines and Pancreas: The Jejunum and the Ileum"
* [http://wwwartsci.clarion.edu/biology/bbarnes/digestivesystem/sm_intestine/villi_draw1.GIF Diagram] at [[Clarion University of Pennsylvania]]
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