Digestion 071410 - DIGESTIVE TRACT Contains: DIGESTION...

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1 (CH. 2) Lia M. Nightingale, Ph.D. DIGESTIVE TRACT Contains: Mouth Esophagus Stomach Small intestine Large intestine Accessory organs (salivary glands, pancreas, gallbladder, liver) MOUTH Chewing food increases ____________ for maximum digestion Salivary glands release saliva Parotid, submandibular & sublingual glands Saliva contains water , electrolytes, enzymes ENZYMES IN THE MOUTH Carbohydrates Lipids Salivary amylase Lingual lipase Proteins NONE ESOPHAGUS Bolus = food + saliva Swallowing is regulated by the medulla Esophageal sphincter relaxes Epiglottis shifts to cover trachea Once bolus is in esophagus, epiglottis reopens ESOPHAGUS Voluntary & involuntary muscles are stimulated by parasympathetic nerves Peristalsis = wavelike motion moving bolus from mouth to stomach
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2 ESOPHAGUS Between esophagus & stomach lies gastroesophageal sphincter (lower esophageal sphincter) Prevents reflux of stomach contents into esophagus (gastroesophageal reflux disorder; GERD) STOMACH J-shaped organ between esophagus & small intestine Empty = ¼ cup Can stretch to ~6 cups STOMACH Four main regions: Cardia receives bolus from esophagus Fundus Body gastric juice production Antrum (distal pyloric region) grinds & mixes food with gastric juice ( peristalsis ) Chyme = partially digested food STOMACH Neck cells secrete mucus Parietal cells secrete HCl & intrinsic factor (IF) Chief cells secrete enzymes Enteroendocrine cells secrete hormones ‘G’ cells STOMACH Gastric juice contains: Water Electrolytes Intrinsic factor Hydrochloric acid Enzymes Mucus Bacteriocide Denatures proteins Converts pepsinogen to pepsin Release nutrients from organic complexes pH ~2 1. Pepsin – endopeptidase 2. Gastric lipase – digests short & medium-chain triglycerides Composed of glycoproteins, Needed to absorb Vitamin B 12 STOMACH Pepsinogen (inactive zymogen ) Pepsin (active enzyme) HCl or pepsin
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3 ENZYMES IN THE STOMACH *Activated enzymes formed from zymogen precursors. Carbohydrates Lipids NONE Gastric lipase Proteins Pepsinogen* PEPTIDE HORMONES AFFECTING THE STOMACH Hormone Site of Release Stimulants for Release Effect on Stomach Gastrin G cells of the antrum, Antrum distention; vagus nerve impulses triggered by site/smell of food; proteins Stimulates HCl secretion & mucosal growth Secretin (opposes gastrin action) S cells of the duodenum, Acidic chyme in duodenum Stimulates pepsinogen secretion; decreases gastric motility Cholecystokinin (CCK) I cells of the duodenum, Fat or protein-rich chyme in duodenum Decreases gastric emptying Gastric inhibitory peptide (GIP) K cells of the duodenum Fatty acids, amino
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This note was uploaded on 01/07/2012 for the course PHCH 51311 taught by Professor Nightingale during the Summer '11 term at Palmer Chiropractic.

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Digestion 071410 - DIGESTIVE TRACT Contains: DIGESTION...

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