- absorptive area increased by plicae circulares, villi and microvilli
- villi extend into lumen
- contain network of fenestrated capillaries
- contain lymphatic capillary (lacteal)
- Mucosa
- intestinal glands (crypts of Lieberkühn)
- simple columnar epithelium
- enterocytes
- absorption
- hence microvilli
- actively move subsstance saround
- secret digestive enzymes
- goblet cells
- mucus secreting
- appear empty in histological section, or stain read with PAS reaction
- Paneth cells
- secrete lysozyme and other enzymes
- regulate gut bacteria
- enteroendocrine cells
- produce cholecystokinin and GIP
- M (microfold) cells
- endocytose macromolecules
- important in immune response of gut
- submucosa
- dense connective tissue
- Brunners glands in duodenum
- secretion in alkali (pH 8.1-9.3)
- muscularis externa
- movements involve segemntation and peristalsis
- smooth muscle
- serosa
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