Digestive System Notes - Digestive System Function Acquires...

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Digestive System Function Acquires nutrients from environment Anabolism Uses raw materials to synthesize essential compounds Catabolism Decomposes substances to provide energy cells need to function Digestive (GI) Tract Actions of Digestive (GI) Tract Ingestion Occurs when material enters via the mouth Mechanical Processing Crushing / Shearing – makes material easier to move through the tract Digestion Chemical breakdown of food into small organic compounds for absorption Digestive (GI) Tract The Digestive Organs and the Peritoneum Lined with serous membrane consisting of Superficial mesothelium covering a layer of areolar tissue Serosa, or visceral peritoneum: covers organs within peritoneal cavity Parietal peritoneum: lines inner surfaces of body wall Histological Structure of the Digestive (GI) Tract Movement of Digestive Materials By muscular layers of digestive tract Consist of visceral smooth muscle Along digestive tract: Has rhythmic cycles of activities ( PERISTALSIS ) Consists of waves of muscular contractions
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Move a bolus along the length of the tract Controlled by pacesetter cells Surrounding the lumen of the tract Cells undergo spontaneous depolarization Triggering wave of contraction through entire muscular sheet Peristalsis Functions of Oral Cavity Sensory analysis Of material before swallowing Mechanical processing Through actions of teeth, tongue, and palatal surfaces Lubrication Mixing with mucus and salivary gland secretions Limited digestion Of carbohydrates and lipids Esophagus A hollow muscular tube About 25 cm (10 in.) long and 2 cm (0.80 in.) wide Conveys solid food and liquids to the stomach Begins posterior to cricoid cartilage Is innervated by fibers from the esophageal plexus Stomach Function Major Functions of the Stomach Storage of ingested food Mechanical breakdown of ingested food Disruption of chemical bonds in food material by acid and enzymes
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Production of intrinsic factor , a glycoprotein required for absorption of vitamin B 12 in small intestine Gastric Anatomy Digestion in the Stomach Stomach performs preliminary digestion of proteins by pepsin Some digestion of carbohydrates (by salivary amylase) Lipids (by lingual lipase) Stomach contents Become more fluid pH approaches 2.0 Pepsin activity increases Protein disassembly begins Although digestion occurs in the stomach, nutrients are not absorbed there Small Intestine 90% of absorption occurs in the small intestine Small Intestine The Duodenum The segment of small intestine closest to stomach 25 cm (10 in.) long “Mixing bowl” that receives chyme from stomach and digestive secretions from pancreas and liver Functions of the duodenum To receive chyme from stomach
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