BIOL 221 Lecture Notes - Lecture 8: Ileocecal Valve, Brush Border, Circular Folds
4 Mar 2020
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Document Summary
The jejunum is the site of most chemical digestion and absorption. By the time the chyme has reached the end of the ileum, digestion by human enzymes is complete and most of the nutrients have been absorbed. The ileocecal valve controls movement of chyme into the large intestine. Numerous peyer"s patches are found in the submucosa of the small intestine. Modifications of the mucosa in the small intestine increase surface area around 6000x compared to a flat mucosa. Large-scale modifications include circular folds called plicae circulares (singular = plica circularis) and the villi (singular = villus) that are served by blood vessels and lacteals. The apical (luminal) membranes of absorptive cells are increased by the presence of microvilli (singular = microvillus) that form the. These microvilli allow the cell to have many more transport molecules than it would if the microvilli were not present.
