Circular folds 5506202 207841360 2008-04-24T12:27:44Z ClueBot 4928500 Reverting possible vandalism by [[Special:Contributions/69.248.101.59|69.248.101.59]] to version by Arcadian. False positive? [[User:ClueBot/FalsePositives|Report it]]. Thanks, [[User:ClueBot]]. (337350) (Bot) {{Infobox Anatomy | Name = {{PAGENAME}} | Latin = plicae circulares | GraySubject = 248 | GrayPage = 1173 | Image = Gray1057.png | Caption = Interior of the descending portion of the duodenum, showing bile papilla. | Image2 = | Caption2 = | System = | Precursor = | MeshName = | MeshNumber = | DorlandsPre = p_24 | DorlandsSuf = 12648947 | }} 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]] {{digestive-stub}} {{Gray's}} {{Digestive tract}} [[sv:Cirkulära veck]]