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Overview: Digestion and Absorption NFSC 303 McCafferty Digestion & Absorption: Overview Digestion: breakdown of nutrients in the GI tract – Mechanical and chemical Absorption: transfer of nutrients through the wall of the GI tract, into circulation Involved in D&A – GI tract – Auxiliary organs: ________________________________ Pancreas: – Exocrine function: – Endocrine function: Liver: (many functions…) – Digestive function: Gallbladder – Digestion Mouth – Mechanical action: biting, chewing – Chemical action: • Saliva • Enzymes – Esophagus – Passage tube to stomach only – Muscular contractions propel food down • Stomach – Mechanical “churning” and peristalsis – Chemical: • water • enzymes • HCl = – – Semi-liquid _______________ – Released into small intestine in small amounts Small Intestine – Most digestion and absorption occur here – Peristalsis and Segmentation • chyme mixed with more enzymes • bicarbonate (to reduce acidity), and • bile (involved in fat absorption) “Lower” small intestine: – – Large Intestine (Colon): – Removes excess water and salts (electrolytes), forms feces. Rectum and Anus: – Feces is held in rectum until eliminated through the anus. Absorption Most absorption occurs in the small intestine… so let’s go back to the small intestine for a moment… Small folds intestine wall – thousands of Nutrients pass through the intestinal cells and then into blood or lymph – Capillaries: – Lymph vessels: Now we have all the nutrients on the inside of the body. – In the next section, we’ll learn all about 1)carbohydrates, 2) digestion and absorption of CHO, and 3) utilization of CHO once inside the body.