| Circular folds | |
|---|---|
 Small intestine (jejunus-ileum) with circular folds. | |
| Details | |
| Location | Small intestine |
| Identifiers | |
| Latin | plicae circulares |
| TA98 | A05.6.01.007 |
| TA2 | 2943 |
| FMA | 15071 |
| Anatomical terminology | |
Thecircular folds (also known asvalves of Kerckring,valves of Kerchkring,plicae circulares,plicae circulae, andvalvulae conniventes) are largevalvular flaps projecting into thelumen of thesmall intestine.
The entiresmall intestine has circular folds ofmucous membrane.[1] The majority extend transversely around thecylinder of the small intestine,[2] for about one-half or two-thirds of itscircumference. Some form completecircles. Others have a spiral direction. The latter usually extend a little more than once around the bowel, but occasionally two or three times. While the larger folds are about 1 cm in depth at their broadest part, most folds are smaller. There tends to be an alternating pattern between larger and smaller folds.[1]
They are not found at the commencement of theduodenum, but begin to appear about 2.5 or 5 cm beyond thepylorus.
In the lower part of the descending portion, below the point where thebile andpancreatic ducts enter the small intestine, they are very large and closely approximated.
In the horizontal and ascending portions of the duodenum and upper half of thejejunum, they are large and numerous.[3] From this point, down to the middle of the ileum, they diminish considerably in size.
In the lower part of theileum, they almost entirely disappear;[4] hence the comparative thinness of this portion of the intestine, as compared with the duodenum and jejunum.[citation needed]
Unlike thegastric folds in thestomach, they are permanent, and are not obliterated when theintestine is distended.
The spaces between circular folds are smaller than thehaustra of thecolon, and, in contrast to haustra, circular folds reach around the whole circumference of the intestine. These differences can assist in distinguishing the small intestine from the colon on anabdominal x-ray.
The circular folds slow the passage of the partly digestedfood along the intestines, and afford an increased surface forabsorption.[5] They are covered with small finger-like projections calledvilli (singular, villus). Each villus, in turn, is covered withmicrovilli. The microvilli absorb fats and nutrients from thechyme.
The circular folds are also called the valves of Kerckring,[3] valves of Kerchkring,[6] plicae circulares,[3][5]plicae circulae,[6] andvalvulae conniventes.[3]
This article incorporates text in thepublic domain frompage 1173 of the 20th edition ofGray's Anatomy(1918)
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