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Digestive system Functions of the digestive system Digestion mechanical and chemical breakdown of material Motility movement of material from the oral cavity to the anus swallowing peristalsis Secretion exocrine release of enzymes into the lumen of the digestive tract for chemical digestion Absorption movement of material from the lumen into the blood stream Alimentary canal or GI tract a continuous tube about 30 feet in length oral cavity esophagus stomach small intestines large int rectum Accessory organs digestive organs outside of canal communicate with GI tract via ducts salivary glands pancreas liver gallbladder teeth tongue Gastrointestinal tractFour layers Tunica mucosa Tunica submucosa Tunica muscularis externa Tunica serosa visceral peritoneum mucosa submucosa muscularis externa serosa Fig 25 2 Tunica mucosa mucus membrane moist epithelial tissue different types loose connective tissue Folding increases surface area Tunica submucosa areolar connective tissue usually contains glands Tunica muscularis externa 2 or 3 layers of smooth muscle 3 in stomach only Tunica serosa connective tissue serous membrane NOT in esophagus rectum adventitia Smooth muscle No sarcomere arrangement No striations Many have no efferent innervation Gap junctions Arranged in sheets Ability to stretch Two forms of contraction Peristalsis segmentation Peristalsis Net movement of material towards the rectum Fig 25 3 Segmentation No net movement of material mixing and churning Enteric nervous system nerves network that control digestive reflexes Visceral parietal peritoneum in folding that suspend organs Falciform ligament connect liver to diaphragm and anterior wall Greater omentum fold laying over large intestines connects the greater curvature of stomach to transverse colon filled with fat globules and lymph nodules lesser omentum from liver to lesser curvature of stomach mesentery proper sm intestines to posterior abdominal wall mesocolon suspends lg intestines from posterior

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