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Digestion Processes Digestion Steps in digestion Ingestion propulsion mechanical digestion chemical digestion absorption and defecation Starts in the mouth mechanical and chemical digestion Chemical digestion through saliva secreted by the salivary gland Salivary glands 1 Parotid glands 2 Submandibular glands 3 Sublingual glands Saliva contains 1 Salivary lingual amylase converts glycogen and starch into simple sugars 2 Salivary lingual lipase enzymes that break triglycerides into fatty acids and glycerol 3 Contains mostly water 4 Note fat and carbohydrate CHO starch digestion starts in the mouth and protein digestion starts in the stomach Mechanical digestion chewing food is called mastication in addition to the tongue moving food intrinsic skeletal muscles are involved in speaking and swallowing deglutition The esophagus connects the laryngopharynx with the stomach A bolus moist ground food a clump of food drops into the esophagus having passed over the epiglottis which prevents aspiration chocking and prevents food from entering the airways during swallowing deglutition From the esophagus food goes to the stomach The stomach and most GI tract have 4 layers gastrointestinal the only exception is the esophagus The stomach is where protein digestion begins Parietal cells of the mucosa secrete HCL and intrinsic factor for vitamin B 12 HCL dentures proteins Chief cells secretes pepsinogen and gastric lipase inactive state in the presence of HCL pepsinogen becomes pepsin active enzyme for protein digestion pepsin digests proteins G cells secrete the hormone gastrin gastrin stimulates the release of more HCL from parietal cells The reason autodigestion of the stomach doesn t occur is 1 The stomach is protected by alkaline mucous membrane 2 Pepsinogen is in its inactive state only when food is present in the stomach and parietal cells secrete HCL does pepsin become active 4 regions of the stomach Trace a bolus until it becomes chyme 1 Cardiac bolus enters 2 Fundus 3 Body most muscular region of the stomach 4 Pylorus chyme for mush is formed Absorption in the small intestine Primary absorption site of nutrients Higher pH Is essential for enzymes to work 7 8 8 1 PH enzymes work best increase bicarbonate product Regions of the small intestine Duodenum receives secretions from the liver gallbladder and pancreas enzymes and bicarbonate Jejunum site of most absorption in small intestine Ileum last section of small intestine The duodenum secrets 2 hormones Cholecystokinin stimulates gallbladder liver and pancreas Secretin stimulus the liver and pancreas to secrete more bicarbonate which raises pH of small intestine Production of enzyme and bicarbonate Cholecystokinin stimulates the pancreas to release its enzymes lipase amylase proteases Proteases released by the pancreas chymotrypsin trypsin carboxypeptidase Cholecystokinin stimulates gallbladder to secrete bile emulsifies fat Secretin stimulates the release of bicarbonate by the pancreas and liver Large intestine Completion of absorption mainly water Production of certain vitamins Formation and elimination of feces Accessory organs of digestion Produces bicarbonate Pancreas located posterior to stomach passes pancreatic juices into the duodenum Liver function include Makes bile stored in gallbladder Makes clotting factors and albumin Detoxifies alcohol and drugs Hematopoiesis blood component production Gallbladder cholecystitis Lipid and protein metabolism Excretes bilirubin Stores bile

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BROCKPORT BIO 202 - Digestion

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