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Lecture 23

BIOL 212 Lecture 23: Digestive System Part 2

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Department
Biology
Course
BIOL 212
Professor
Garver
Semester
Spring

Description
Lecture #23 - The Digestive System Part 2 [4/26/17] I. Retroperitoneal Space A.Digestive organs 1.Ascending and descending colon 2.Rectum 3.Pancreas 4.Duodenum B.Other organs 1.Kidneys and adrenal glands 2.Ureters [come off the kidney] 3.Aorta and inferior vena cava II. Gastrointestinal [GI] tract - aka digestive tract or alimentary canal A.The mouth - aka oral cavity 1.Flexible lips and muscular cheeks to hold food in 2.Uvula helps guide food down pharynx [as opposed to going up into the nasal cavity] 3.Muscular tongue [anchored my lingual frenulum] moves food over teeth for mastication a)Teeth covered with hardest substance produced by the body - enamel B.Esophagus 1.One foot long muscular tube moves food to stomach 2.Lined with protective stratified squamous epithelia 3.Uses peristalsis - crunch up, push from behind, directing things down to stomach 4.Muscle throughout the esophagus a)⅓ of length of the esophagus is skeletal muscle b)Middle ⅓ is a mix of skeletal and smooth muscle c)Last ⅓ is smooth muscle only 5.Lower sphincter weak a)Stomach acids may move up into lower esophagus b)Acid reflux - damage tissue C.Stomach - root word gastro- 1.Function in protein digestion [breakdown] a)Amylase breaks down carbohydrates in mouth b)Rugae - nonpermanent folds 2.Gastric glands secrete pepsin -> protein a)Chief cells -> pepsinogen b)Parietal cells -> HCl c)Pepsinogen + HCl → Pepsin → protein 3.Stomach pH ~2-3 4.Three muscle layers allow for strong contractions [segmentation] a)circular, longitudinal, and oblique b)only in stomach 5.Large of amounts of alkaline mucus coats stomach to protect against self destruction [by the acidic pepsin] 6.Stomach absorbs… a)Water b)Electrolytes c)Some drugs [aspirin] d)Alcohol [the stomach secretes alcohol dehydrogenase to break down alcohol before it
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