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DIGESTION

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					DIGESTION

  The process of preparing your
   food for absorption
What do you know about the
digestive system?
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
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
DIGESTION:
THE ESOPHAGUS
 Connects   the pharynx and the stomach
 Bolus is moved towards the stomach by
  a contractile movement called
  peristalsis. Extra Credit??
 Allows food to move through thoracic
  cavity, through diaphragm, to peritoneal
  cavity and the stomach
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
DIGESTION:
STOMACH
 Stops  salivary amylase and slows
  lingual lipase activity (acid denatures
  enzyme)
 Starts protein digestion: pepsin
  activated and starts protein digestion
What does the hydrochloric acid
of the stomach do to protein?
1.   adds amino acids
     to it
2.   Denatures it
3.   Provides
     additional CHO
     for it
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4.   Preserves it


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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
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)
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
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
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
What enzyme in the stomach starts
the chemical breakdown of protein?
1.   lipase
2.   carbohydrase
3.   pepsin
4.   Hydrochloric acid
5.   sucrase
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DIGESTION:
LIPIDS
 Mouth: Lingual Lipase, very little activity
 Stomach: very little activity
 Small Intestines: Major activity
   Bilefrom gall bladder emulsifies
   Enzymes from pancreas digest and makes
    the products ready for digestion
      monoglycerides, glycerol, fatty acids
      absorbed into cells of microvilli
Digestion of CHO begins in the
mouth with
1.   lingual lipase
2.   salivary amylase
3.   pancreatic source
     enzymes
4.   liver source
     enzymes                               0% 0% 0% 0% 0%

5.   None of the above
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Generally, where do the enzymes that break
down the large molecules such as starch, and
protein, come from?

1.   The mouth
2.   The stomach
3.   The small
     intestine
4.   The pancreas
5.   The large                            0%         0%          0%           0%           0%
     intestine



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posted:10/20/2011
language:English
pages:17