BIOL 221 Study Guide - Final Guide: Gastrointestinal Tract, Muscular Layer, Brush Border
11 Feb 2020
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Document Summary
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 circularis (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 brush border . These microvilli allow the cell to have many more transport molecules than it would if the microvilli were not present. Some of the integral membrane proteins serve as brush border enzymes and are important to the digestion of disaccharides and di- and tripeptides. Goblet cells secrete mucus that helps to protect the wall of the intestine from chemicals in the lumen. Absorptive cells are joined by tight junctions so that nutrients must pass through the cells to be absorbed. Microvilli contain enzymes and transporters important to digestion and absorption of nutrients.
