GI system lectures 30-33 W2012

GI system lectures 30-33 W2012 - The Gastrointestinal...

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The Gastrointestinal System Lectures 30 - 33 Recommended reading Sherwood 7 th edition Chapter 16 pp. 589-637
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Topics to be covered in these lectures Overview of the Gastrointestinal (Digestive) System A. Primary jobs of the GI system B. Other functions Overview of Digestive Processes A. Ingestion B. Secretion C. Propulsion and mixing (Motility) D. Digestion E. Absorption General structure of the digestive tract A. Serosa B. Muscularis externa C. Submucosa D. Mucosa Detailed Structure and Function of the Digestive Tract (section by section) A. Buccal cavity (mouth) B. Pharynx and Esophagus C. Stomach D. The small intestine and accessory organs 1. The pancreas and its exocrine secretions 2. The liver E. Final steps of digestion and absorption in the small intestine 1. Carbohydrate absorption 2. Protein absorption 3. Fat absorption F. Large Intestine
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Gastrointestinal (Digestive) System A. Primary jobs of the GI system: – We are heterotrophs: must obtain nutrients from environment – Must break down food stuff into absorbable units – Must allow assimilation of units (absorption) – Must respond, change,and adjust to different food types B. Other functions - Role in water and ion balance - Vitamin absorption - Cholesterol and iron homeostasis It ` s activities are controlled by an intricate and overlapping network of nerves and hormones : =>The term l hormone z was first used to describe secretin =>The digestive tract has its own autonomously functioning nervous system ( the enteric nervous sytem ) with more neurons than in the spinal cord
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Digestive Processes A. Ingestion - Move food into digestive tract B. Secretion - 1) EXOCRINE secretions (ie into digestive tract lumen, essentially OUTSIDE the body) Secretion under neural and hormonal control Promote digestion, adjust tonicity, lubrication -Enzymes, acid, buffers, electrolytes, H 2 O We produce as much as 10 liters per day; 88-90% reabsorbed 2) ENDROCRINE secretions (ie INSIDE body into blood stream) i.e. Hormones Regulate digestive tract and non-digestive tract functions : Control both motility/contraction and secretions, as well as food intake and energy balance
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Digestive Processes, cont. C. Propulsion and mixing- muscular activity of digestive tract: primarily smooth muscle Two primary motor activities: 1) Peristalsis (throughout) 2) Segmentation (mostly small intestine) Fig. 16-19, p. 621 Fig. 16-6, p. 600
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-Breakdown of structurally complex foodstuffs into small absorbable units 1) Mechanical digestion: Chewing, and contractions in GI tract 2) Chemical digestion: Enzymatic hydrolysis a) Carbohydrates (60-80% of diet, major caloric source) Starches: amylose and amylopectin (linear and branched polysaccharides) Lactose (galactose- β -1,4-glucose) (disaccharide) Sucrose (glucose- α -1,2-fructose) ( ) Maltose (glucose- α -1,4-glucose) ( ) Glucose (monosaccharide) Fructose ( ) Monosaccharides are absorbable units Digestive Processes, cont. Fig. 16-1, p. 591
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This note was uploaded on 04/05/2012 for the course NPB 101 taught by Professor Fuller,charles/goldberg,jack during the Spring '08 term at UC Davis.

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GI system lectures 30-33 W2012 - The Gastrointestinal...

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