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The circular folds slow the passage of the partly digested food along the intestines, and afford an increased surface for absorption. [5] They are covered with small finger-like projections called villi (singular, villus). Each villus, in turn, is covered with microvilli. The microvilli absorb fats and nutrients from the chyme.
The digestive tract continues as the jejunum which continues as the ileum. The jejunum, the midsection of the small intestine contains circular folds, flaps of doubled mucosal membrane which partially encircle and sometimes completely encircle the lumen of the intestine. These folds together with villi serve to increase the surface area of the ...
The circular muscle layer prevents food from travelling backward and the longitudinal layer shortens the tract. The thickness of the muscular layer varies in each part of the tract: In the colon, for example, the muscular layer is much thicker because the faeces are large and heavy and require more force to push along.
Circular folds are transverse folds that slow the passage of the luminal contents and serve to expand the total surface area threefold. Villi and intestinal glands serve to increase the mucosal surface area tenfold. (Intestinal villus) Microvilli covering the apical surface of the enterocytes increase the absorptive surface twentyfold.
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus.The GI tract contains all the major organs of the digestive system, in humans and other animals, including the esophagus, stomach, and intestines.
It appears rounded and is often covered by a fold on the uppermost side of the papilla; that is, the side which receives contents from the stomach. [4] The major duodenal papilla is seen from the duodenum as lying within a mucosal fold. The minor duodenal papilla is situated 2 cm proximal. [2]
These folds are about 12 mm. in width and are composed of the circular muscle coat of the rectum. They are usually three in number; sometimes a fourth is found, and occasionally only two are present. One is situated near the commencement of the rectum, on the right side.
Intestinal villi (sg.: villus) are small, finger-like projections that extend into the lumen of the small intestine.Each villus is approximately 0.5–1.6 mm in length (in humans), and has many microvilli projecting from the enterocytes of its epithelium which collectively form the striated or brush border.