Ch25_Digestion

Ch25_Digestion - Digestive system Functions of the...

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Digestive system
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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
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• Alimentary canal or GI-tract- a continuous tube – about 30 feet in length – oral cavity Æ esophagus Æ stomach Æ small intestines Æ large int. Æ rectum • Accessory organs- digestive organs outside of canal – communicate with GI tract via ducts – salivary glands, pancreas, liver, gallbladder, teeth, tongue
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Gastrointestinal tract- Four layers: Tunica mucosa Tunica submucosa Tunica muscularis externa Tunica serosa- visceral peritoneum mucosa submucosa muscularis externa serosa
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Fig 25.2
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• 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
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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
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This note was uploaded on 11/10/2011 for the course PDBIO 220 taught by Professor Tomco during the Winter '09 term at BYU.

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Ch25_Digestion - Digestive system Functions of the...

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