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Digestion

Digestion. Mechanical Digestion : Break down of large food pieces into smaller pieces Teeth and hard palate help in this process. Chemical Digestion : enzymes chemically change the food into other substances saliva, stomach acid, liver and pancreatic juices help in this process.

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Digestion

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  1. Digestion • Mechanical Digestion: Break down of large food pieces into smaller pieces • Teeth and hard palate help in this process

  2. Chemical Digestion: enzymes chemically change the food into other substances • saliva, stomach acid, liver and pancreatic juices help in this process

  3. Pathway of Food • Food enters the mouth • Bolus passes through the pharynx • Bolus goes down the esophagus (peristalsis) • Bolus passes the cardiac sphincter into the stomach (“food” now called chyme)

  4. Chyme passes the pyloric sphincter and enters the small intestine • nutrients absorbed in small intestine • Undigested food circulates in the large intestine • water is absorbed in large intestine • waste is released out the anus

  5. The Stomach A J-shaped organ with thick walls that lies beneath the diaphragm

  6. Stomach continued • Stores food • Helps in digestion (no food is absorbed in stomach) • Connects to esophagus (top) and duodenum/small intestine (bottom) by sphincters • Contains gastric juices (produced by gastric glands) • Produce pepsin • Produce hydrochloric acid

  7. Gastric Juices contain: -Pepsin (breaks down protein) -HCl (causing stomach=pH2) breaks down food kills bacteria • The stomach wall is protected by mucus produced by globet cells • An ulcer (open sore) is formed when the stomach wall breaks down gradually from acid

  8. Food leaves the stomach in the form of chymeenters small intestine/duodenum.

  9. Small Intestine (3-6 meters in length, small diameter) • Parts of the Small Intestine -First 25cm=duodenum -connects to liver and pancreas -liver produces bile (emulsifies fat) -pancreas releases pancreatic juices (enzymes) -digestion finishes here Other two parts: jejunum and ileum where particles are absorbed in blood stream

  10. small intestine • Surface area=size of tennis court -villi (fingerlike projections) -microvilli (contain enzymes and are called brush-border enzymes)

  11. Sugars and Amino Acids -pass through to blood vessel (cardiovascular system) • Fats-enter smooth ER or Golgi and enter the lymphatic system • digestion review • http://kitses.com/animation/swfs/digestion.swf

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