System II
2026-2027 Updated
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, Structures in small intestine that increase surface area circular folds, villi, microvilli
Intestinal crypts tubular glands scattered between villi
Five main cell types found in villi and crypts enterocytes (main), enteroendocrine, goblet, paneth, stem cells
Enterocytes are simple columnar cells bound by tight junctions that contain many microvilli
Function of enterocytes in villi absorb nutrients and electrolytes
Function of enterocytes in crypts produce intestinal juice that's a watery mixture of mucus that carries chyme
Goblet cell function in small intestine mucus-secreting cells found in epithelia of villi and crypts
Enteroendocrine cells in small intestine secrete secretin and cholecystokinin (CCK)
Paneth cells in small intestine secrete defensins and lysozymes
Stem cells in small intestine continuously divide to produce other cell types
Mucous associated lymphoid tissue function protects intestine against microorganisms
MALT includes 1. individual lymphoid follicles
2. Peyer's patches (aggregated lymphoid nodules) in lamina propria
Lamina propria in MALT has large number of plasma cells that secrete IgA
Submucosa tissue type areolar connective tissue
Duodenal glands of the duodenum submucosa secrete alkaline mucus to neutralize acidic chyme from the stomach
Intestinal juice secreted in response to distention or irritation of mucosa