Test 1 Notes - Lecture 3 September 5, 2007 Digestion,...

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Lecture 3 – September 5, 2007 Digestion, Absorption, Transport of Nutrients Digestion -Inputs: water/food, oxygen; what’s not absorbed is excreted. We absorb nutrients that produce end product waste product in the blood system. Waste system is thru the urine. -What: preparation of food nutrients for absorption into the body so they’re in the form that can be absorbed in the body. Digestion is preparation of food nutrients so that it can be absorbed into the body. -Where: Gastro intestinal (GI) tracts – tube outside of the body: goes thru mouth and thru anus – put things in and put things out. It protects body from absorbing potentially harmful nutrients or compounds by acting as a physical barrier and immune system in GI tract helps to destroy/kill potentially harmful microbes. It’s selective of what’s actually absorbed -Process: 3 basic aspects -Anatomy of GI tract -Muscle action of those organs -Secretions (chemical digestion): enzymes – facilitate and speed up chemical reactions; digest thru hydrolysis – split food using water Hormones – primarily regulators – they regulate digestive process -GI Tracts Anatomy 1) Mouth beginning of GI tract; saliva lubricates the food. Teeth = important for prepping food into small pieces that can be exposed to secretions in the stomach. Important to allow people to consume a wide variety of foods and allows them to chew them into small enough pieces. Secretion of saliva lubricates the food. 2) Swallowing – muscle action: peristalsis = the wave like action down the muscular tube that brings food from mouth to stomach . For food to reach stomach, food must go thru esophagus and pass thru esophageal sphincter . Sphincter – ring like muscle that closes door btwn esophagus and stomach- esophageal sphincter has to relax for the food to enter ; helps keep food and stomach contents in stomach. 3) Stomach – large sac that holds at least a quart – stores food that we eat and also prepare the food for further digestion. Muscle action is very important b/c it helps break down food into smaller pieces (smaller than what comes in thru mouth) as well as mix contents of stomach w/digestive secretions. Walls are longitudinal, diagonal, circular. Walls twist and turn in order to mix and break down food. Major secretions from stomach walls = pepsin ( secreted in the form of pepsinogin ) and presence of HCl changes pepsogin to pepsin. Pepsin = a protease = a enzyme that hydrolyzes protein. HCl functions: help destroy bacteria that we’ve consumed in foods promotes denaturing of proteins (long molecules that are folded on top of each other w/3 or 4-D configuration). In order for digestive enzymes to come in contact, that molecule needs to be denatured and spread out so that there’s more SA aval for digestive enzymes activates pepsonigin frees vitamin B12 enhance absorption of Fe, Ca by keeping them in the reduced state in the stomach (more easily absorbed later in the GI tract)
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Test 1 Notes - Lecture 3 September 5, 2007 Digestion,...

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