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Digestion as a Process

Digestion as a Process. Alimentary, my dear watson …. Digestion. Def: Changing of foods to a form that can be absorbed and used by cells Occurs in alimentary canal Consists of both mechanical and chemical types. Mechanical digestion. Break down food into tiny particles

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Digestion as a Process

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  1. Digestion as a Process Alimentary, my dear watson…

  2. Digestion Def: Changing of foods to a form that can be absorbed and used by cells Occurs in alimentary canal Consists of both mechanical and chemical types

  3. Mechanical digestion • Break down food into tiny particles • Mix them with digestive juices (produces a bolus) • Move them along digestive tract • Eliminates digestive wastes from the body

  4. Involves: • Chewing (mastication) • Swallowing (deglutition) • Peristalsis (wave-like contractions that move down a tube) • Defecation (elimination)

  5. Chemical digestion • Breaks up large, non-absorbable food molecules into compounds having smaller molecules • Can then pass through intestinal mucosa into blood/lymph • Brought about by digestive enzymes

  6. Carbohydrate digestion (Monosaccharide) (Disaccharide) (Polysaccharide)

  7. Carbohydrate digestion • Carbs = Sugars, starches • Starts in mouth, w/ salivary amylase • Mainly in small intestine • Pancreatic amylase – changes starches to maltose (disaccharide) • Intestinal juice enzymes • Maltase– changes maltose to glucose* • Sucrase– changes sucrose to glucose* • Lactase– changes lactose to glucose* • *Monosaccharide

  8. Lactose intolerance?

  9. Lactose Intolerance • Individual cannot synthesize lactase • Lactose passes undigested into large intestine • Here, bacteria (which have lactase) break down lactose, resulting in a “double whammy” • Releases gas • Plus… • Lactose is “osmotically active” • So… it draws water into your intestine… causing diarrhea.

  10. Protein digestion • Starts in stomach • Completed in small intestine • Gastric juice enzymes, rennin (in infants) and pepsin, partially digest proteins • Pancreatic enzyme, trypsin, completes digestion of proteins to amino acids • Intestinal enzymes, peptidases, complete digestion of partially digested proteins to amino acids

  11. Fat digestion • Bile • Not an enzyme • Emulsifies fats (breaks fat droplets into very small droplets) • Pancreatic lipase • Changes emulsified fats to fatty acids and glycerol in small intestine

  12. Absorption • Definition: Digested food moves from intestine into blood or lymph • Enhanced by: • Plica(folds in the lining mucosa) • Villi • Microvilli

  13. Absorption site: • Foods (and most water) absorbed within small intestine • Some water also absorbed through large intestine

  14. Where does it all go?

  15. Your task? • Using your textbook, fill out the chart on digestive structures • Describe their role in digestion

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