 Two Key Functions:
 Digestion - breaking
down food into
smaller molecules
(nutrients).
 Absorbing these
nutrients into the
bloodstream
MECHANICAL
CHEMICAL
 Parts
 Mouth
 Pharynx
 Esophagus
 Stomach
 small intestine
 Liver
 Gallbladder
 Pancreas
 large intestine
 Rectum
 Mechanical Digestion
 Tongue and teeth work
together to break down
food mechanically
 Chemical Digestion
 Amylase - enzyme in
saliva that breaks the
carbohydrates
 Starch
Simple Sugars
 No digestion
 Food is directed from mouth to stomach using peristalsis
 Epiglottis – flap of cartilage
 Ensures food travels to esophagus and not wind pipe (larynx)
 Large muscular sac that continues digestion
 Acidic pH – 2-3 on the pH scale
 Cardiac sphincter – circular muscle that keeps food in
stomach
 Mechanical Digestion  Peristalsis
 Chemical Digestion – protein digestion begins here
 HCL and Pepsin - pepsin (enzyme) and hydrochloric acid begins
protein digestion.
 HCL changes inactive enzyme, pepsinogen  active
pepsin
 Chyme - mixture of stomach fluids and food produced in the
stomach by contracting stomach muscles
 Digestion is completed and nutrients are absorbed here.
 Small in diameter, not in length (> 6m)
 Chemical Digestion completed here.
 Digestion
 Intestinal Enzymes
 Pancreatic amylases – starch
 Peptidases (trypsin, chymotrypsin) – proteins 
amino acids
 Nucleases – nucleic acids  nucleotides
 Lipases – break down fat
 Nutrient Absorption – Villi (villus-singular) – millions of
fingerlike projections (latter portion of small intestine)
 Increase surface area
 Liver - large organ just above the
stomach that produces bile, a
fluid loaded with lipids and salts
 Produces bile that digests fat
 Sends bile to gallbladder for
storage
 Gallbladder
 Stores bile
 Cholesterol
Deposits
(gallstones)
 Pancreas
 Secretes
peptidases –
protein digestive
enzymes
 large intestine
 No digestion
 2 major functions
 Egestion – removal of
undigested waste
 Rectum – stores
feces for release
 Anus – Releases
feces
 Reabsorption
 Water is absorbed
 Belching / Burping
 swallowed air, eat fast, improperly fitted dentures, & chewing gum
 Intestinal gas
 foods rich in fiber, starches, & sugar
 beans, dairy, some vegetables
 bacteria in the GI
 fat substitutes
 GERD - gastroesophageal reflux disease
 painful, persistent heartburn (acid in esophagus)
 cause: hiatal hernia, cigarette smoking, alcohol, overweight, pregnancy,
chocolate, citrus, spicy or fried foods, large high-fat meal
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 Peptic ulcers
 areas of GI eroded by HCL & pepsin
 Helicobacter pylori – bacteria
contributes to production of
gastric & duodenal ulcers
 Food allergy
 hypersensitivity reaction of immune
system
 Food intolerance
 GI gas, pain, diarrhea, or constipation
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 Celiac disease (celiac sprue)
 genetic disorder
 inability to absorb gluten - protein in wheat, rye, & barley
 Immune cells damage the small intestine
 leads to poor nutrient absorption
 requires a diet lacking wheat, rye, & barley
 early diagnosis avoids delayed growth & malnutrition
 Crohn’s disease
 inflammatory bowel can affect any area of the GI tract
 possible immune system reaction to a virus or bacteria
 diarrhea, abdominal pain, rectal bleeding
 weight loss, fever, anemia
 children can experience delayed growth
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 Ulcerative colitis
 chronic disease of the colon
 inflammation & ulceration of inner most lining
 possible immune response to a virus or bacteria
 symptoms are similar to Crohn’s disease
 not caused by food
 patients may avoid foods that cause discomfort
 Diarrhea
 frequent passage of loose, watery stools
 Infection, stress, food intolerances
 reactions to medications, or bowel disorders
 can lead to severe dehydration
 more dangerous for children & the elderly
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 Constipation
 infrequent hard, small, difficult to pass stools
 prevention includes fiber-rich foods & regular exercise
 Irritable bowel syndrome (IBS)
 interferes with normal colon function
 abdominal cramps & bloating
 diarrhea or constipation
 stress, caffeine, large meals, chocolate, alcohol, dairy, wheat
 more common in women
 treatment includes stress management, high fiber diet, fluids,
avoiding offending foods
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