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Digestive SystemOct 2010.ppt - Nutrition 120

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Digestive SystemOct 2010.ppt - Nutrition 120 Powered By Docstoc
					Digestive
 System
 Mouth
           Esophogus


Liver
              Stomach
              Pancreas
              Large intestine
             Small intestine

         Rectum
         Anus
Digestion: Accessory Organs
               • Liver

               • Gall Bladder

               • Pancreas
            Digestion
• The process of PHYSICALLY
  (mechanically) and CHEMICALLY…
Changing the composition of food
  into simpler substances that your
  cells can use for growth, repair
  and maintenance.
        Digestive System
• As food is digested, it passes through
  a muscular tube leading from the
  mouth to the (GASTROINTESTINAL
  TRACT/ GI TRACT).
• The GI tract is about 25 to 30 feet
  in length and each part plays very
  important functions!
 Digestion: Physical/Mechanical
            Changes
• Grinding and mixing by teeth
  (MASTICATION) in the mouth and
  muscular actions of the stomach and
  small intestine and…
• Liquefying by the addition of water
  and digestive juices in the mouth,
  stomach and small intestine
Digestion: Chemical Changes
• In Chemical Digestion, food is mixed
  with powerful acids and enzymes!
• Complex nutrients are broken down
  into particles usable by cells:
- Polysaccharides and disaccharides to
  monosaccharides (carb chains)
- Proteins to amino acids
- Fats to fatty acids to glycerol
Chemical Environment of the GI
            Tract
               Neutral in mouth
               - (pH approx 7)

               Acid in stomach
               - (pH approx 2)

               Neutral in small
                  intestine
               - (pH approx 7)
         Enzymes
•Big food molecules can’t pass
through cell walls.
•ENZYMES are types of proteins used
to break up big molecules into small
ones (they act like chemical scissors).
•These small molecules can pass
through the wall of the small
intestine into the blood. They then
pass into cells and are used.
                       Big food molecules
                     can’t pass through cell
                              walls.


                       ENZYMES are used
                       to break up big
                       molecules into small
                       ones (they act like
These small            scissors).
molecules can
pass through the
wall of the small
intestine into the
blood.
         Digestion: Mouth
• Physical Changes:
- First step in
  digestion
- Teeth grind food
-Salivary glands add
  water (99%)

• Chemical Changes:
-Salivary amylase
 (digests starch…big
 sugars)
       Digestion: Esophagus
• Transport tube (10
  inches)
• Muscular (muscular
  contractions move the
  food - peristalsis)
• Enables swallowing to
  move bolus (food) from
  the mouth to the
  stomach
• No enzymes added
• Other tube in the
  throat region?
  Digestion: Stomach (3 hrs)
• pH Shift
• Inflow of gastric juice containing HCL
  (hydrochloric acid)…almost as strong as
  battery acid!!
• pH rapidly decreases
• Mucus (thick fluid) helps soften and
  lubricate food and protect it from the
  acids
• Protein digestion begins in the stomach as
  the major gastric enzyme that begins to
  break down protein is PEPSIN.
• The mixture of food and juices is called
  chyme…and it moves to the SI next!!
Digestion: Small Intestine(SI) –
           5-14 hours
• About 95% of digestion takes place in SI
• Coiled and folded
• Made of 3 sections: duodenum (12 inches),
  jejunum (4ft) and ilium (5ft)….can stretch
  to over 20 feet!!
• Peristalsis moves food through the SI
• Another pH shift…what happens?
• Site of NUTRIENT ABSORPTION!!!
• Walls of intestine pleated with folds
  covered with villi. (increase surface area)
  Digestion: Large Intestine
  (aka: colon) – up to 3 days
• The small intestine is
  connected to the large
  intestine (3-5 feet
  long in the body…5-6
  stretched)
• Chyme is very liquid
  when enters the LI, so
  main function is to
  ABSORB WATER!!
• Solid wastes called
  feces leave through
  the rectum and then
  finally out the anus
  (mucus/bile/cells from
  lining of LI and water)
        Accessory Organs
• Pancreas – gland behind stomach –
  secretes bicarbonate to neutralize
  environment of SI, produces 3 digestive
  enzymes to break down carbs, pro, fat.
• Liver – large gland above stomach.
  Produces digestive juice called bile.
  (Helps to digest fat)
• Gall Bladder – muscular sac that stores
  bile
Match the organ to its function!!
 Mouth      1. This is where water is absorbed.

            2. Makes bile which breaks up fats and it is alkaline to
Esophogus
            give the right pH for the enzymes in the S. intestine.

Stomach     3. Makes all 3 enzymes.
            4. Mixes the food with enzymes that digest proteins
  Liver
            AND contains acid to kill bacteria.
            5. Produces more enzymes AND this is where the food
Pancreas
            is absorbed through the gut wall into the blood.
  Small     6. Chew and mix the food with saliva (contains
intestine   enzymes).
  Large
            7. Links the mouth to the stomach.
intestine
            8. Here food that can’t be digested is stored as
 Rectum
            faeces and then leaves through the anus.
Well
Done!!

				
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posted:3/3/2012
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