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DIGESTION The process of preparing your food for absorption http://www.mhhe.com/cgi- bin/netquiz_get.pl?qfooter=/usr/web/home/mhhe/biosci/genbio/animation_quizz es/animate_30fq.htm&afooter=/usr/web/home/mhhe/biosci/genbio/animation_qu izzes/animate_30fa.htm&test=/usr/web/home/mhhe/biosci/genbio/animation_qui zzes/animate_
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What Happens to the Food We Eat?
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Digestion To break nutrients into smaller molecules Physical Digestion Mechanical breakdown of food particles Chemical Digestion Enzyme catalyzed breakdown of nutrient molecules
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Absorption Movement of digested nutrients through intestinal wall into: Blood (water soluble nutrients) Lymphatic system - > blood (fat soluble nutrients
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Digestion: The Mouth Chewing: physically breaks down food into smaller components Food stimulates salivary glands to release saliva –Saliva contains amylase-breaks down starch –Saliva moistens food for easy swallow Bolus: ball of chewed food mixed with saliva
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DIGESTION: THE PHARYNX Area responsible for swallowing During swallowing, air passage is blocked by epiglottis –Blocks the food from entering the trachea and the lungs –Bolus is directed down the esophagus
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DIGESTION: THE ESOPHAGUS Connects the pharynx and the stomach Bolus is moved towards the stomach by a contractile movement called peristalsis Allows food to move through thoracic cavity, through diaphragm, to peritoneal cavity and the stomach (peristalsis)
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Digestion: Chewing
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Digestion: Swallowing
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DIGESTION: THE STOMACH Food passes through a sphincter, (esophageal sphincter) a valve Bolus mixes with stomach secretions to become chyme HCl denatures proteins and kills bacteria Mucus protects stomach wall from acid Chyme released into small intestine through pyloric sphincter
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DIGESTION: STOMACH Stops salivary amylase and and slows lingual lipase activity (acid denatures enzyme) Starts protein digestion: pepsin activated and starts protein digestion Two Australians win Nobel Prize in medicine - More Health News - MSNBC.com
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Digestion: The Stomach
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DIGESTION: SMALL INTESTINE 20 feet in length divided into three segments: –duodenum –jejunum –ileum 95% of digestion occurs in small intestine Bile: made in liver, stored in gall bladder –Emulsifies fats
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Digestion: Accessory Organs
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Absorption
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DIGESTION: SMALL INTESTINES Pancreas: –Secretes bicarbonate into duodenum to neutralize stomach acid in the chyme –Secretes enzymes that act on protein (proteases) carbohydrate (carbohydrases) lipids (lipases)
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DIGESTION: LARGE INTESTINES Absorbs water and some minerals Supports growth of bacteria that produce Vitamin K Supports growth of other bacteria that partially breaks down fiber –We are then able to absorb some of the breakdown products
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Absorption and Transportation All nutrients must pass through intestinal lining Picked up by capillaries or lymphatic vessels
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DIGESTION: CARBOHYDRATES Begins in the mouth: salivary amylase –Amylase denatured in stomach Small intestine: pancreatic enzymes breakdown large CHO’s(starch) to smaller Small intestines: brush border cells produce disaccharidases (sucrase, maltase, lactase) –Breakdown sucrose, maltose, lactose Absorption occurs in duodenum & jejunum
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DIGESTION: PROTEIN Protein digestion begins in the stomach –Denaturation by HCl –Pepsin breaks large proteins into smaller peptides Pancreatic enzymes introduced into the duodenum –Break down peptides into amino acids, di- and tri- peptides –Intestine enzymes breakdown to amino acids
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DIGESTION: LIPIDS Mouth: Lingual Lipase, very little activity Stomach: very little activity Small Intestines: Major activity –Bile from gall bladder emulsifies –Enzymes from pancreas digest and makes the products ready for digestion monoglycerides, glycerol, fatty acids absorbed into cells of microvilli
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Other Systems Cardiovascular Hormonal and Nervous Storage –Liver –Muscle –Fat
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