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PowerPoint® Lecture Slide Presentation
by Patty Bostwick-Taylor,
Florence-Darlington Technical College
Digestive System
--if you’ve got the guts to try it.
14
PART A
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The Digestive System Functions
1)
2)
3)
4)
5)
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The Digestive System Functions
1) Ingestion—
2) Secretion—
3) Digestion—
4) Absorption—
5) Defecation—
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The Digestive System Functions
1) Ingestion—eating food
2) Secretion—adding cell products to food
3) Digestion—breaking down food (mechanical & chemical)
4) Absorption—getting nutrients into bloodstream
5) Defecation—rids body of indigestible waste
Insert your own poop joke here
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To accomplish these tasks: Mechanical
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To accomplish these tasks: Mechanical
1) Chewing
2)
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To accomplish these tasks: Mechanical
1) Chewing
Do you need a definition?
2) Swallowing
3) Churning/mixing
4) Moving
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To accomplish these tasks: Mechanical
1) Chewing—mastication
2) Swallowing—deglutition
3) Churning/mixing
4) Moving—peristalsis
These break up food into smaller
pieces. This exposes more food to
digestive enzymes.
More to come
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To accomplish these tasks: Chemical
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To accomplish these tasks: Chemical
Secretions from glands and mucosa contain
enzymes that break chemical bonds in food.
Bile helps emulsify fats in the diet.
More to come
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Organs of the Digestive System
Figure 14.1
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Organs of the
Alimentary Canal
Accesory organs
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Organs of the
Alimentary Canal
Accesory organs
 Mouth
 Tongue
 Pharynx
 Teeth
 Esophagus
 Salivary glands
 Stomach
 Pancreas
 Small intestine
 Liver
 Large intestine
 Gall bladder
 Anus
 (appendix?)
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Organs of the
Accesory organs
3 parts (only 2
Alimentary Canal
in digestive
 Mouth
system  Tongue
 Pharynx
 Teeth
 Esophagus
 Salivary glands
 Stomach
3 parts
 Pancreas
 Small intestine
 Liver
 Large intestine
 Gall bladder
 Anus
 (appendix?)
6 (?) parts
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From the top:
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Mouth (Oral Cavity) Anatomy
Figure 14.2a
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Mouth (Oral Cavity) Anatomy includes:
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Mouth (Oral Cavity) Anatomy includes:
 Lips (labia)
 Teeth
 Cheeks
 Gingivae (gums)
 Hard palate
 Salivary glands
 Soft palate
 Tonsils—Palatine and
Lingual
 Uvula
 Vestibule
 Tongue
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Mouth (Oral Cavity) Anatomy
Figure 14.2a
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Mouth (Oral Cavity) Anatomy
Figure 14.2b
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Mouth Physiology—Alternate airway and Piehole
 What does the mouth do in the digestive system?
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Mouth Physiology
 What does the mouth do in the digestive system?
 Mastication (chewing) of food
 Mixing chewed food with saliva—contains
salivary amylase to begin chem. digestion of
carbohydrates
 Initiation of swallowing by the tongue
 Allows for the sense of taste
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Pharynx Anatomy
Figure 14.2a
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Oropharynx & Laryngopharynx Physiology
(Nasopharynx—not part of the digestive
system)
 Passes air and food
 Food is propelled to the esophagus by
two muscle layers: a longitudinal inner
layer and a circular outer layer
 A bolus (ball) of food is moved by
peristalsis: an alternating contraction of
the muscle layers
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Oropharynx & Laryngopharynx Physiology
(Nasopharynx—not part of the digestive
system)
 Passes air and food
 Food is propelled to the esophagus by
two muscle layers: a longitudinal inner
layer and a circular outer layer
Consistent throughout
digestive system
 A bolus (ball) of food is moved by
peristalsis: an alternating contraction of
the muscle layers
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That’s the end of the mixed systems
…the following refers to all parts of the GI tract
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Peristalsis
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Peristalsis
For motion
For mixing
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Peristalsis.
 Muscles in the GI tract include longitudinal and
circular muscles.
 When circular muscles contract, they squeeze
their tube smaller.
 A wave of contractions like this forces a bolus
(ball) of food or waste along its way
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Unusual Structures to come:
 Lumen
 Rugae
 Epiglottis
 Sphincters
 Villi
 Lacteals
 Appendix
 Mesentery
 Peritoneum
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Unusual Structures to come
 Lumen—the center of a tube
 Rugae—folds in the lining of the stomach
 Epiglottis—covers the trachea during swallowing
 Sphincters—circular muscles that close a tube
 Villi—projections on lining for more surface area
 Lacteals—center of a villus, lead to lymph vessel
 Appendix—could be vestigal
 Mesentery—membrane attached to intestines
 Peritoneum—lining of the abdominal cavity
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Layers of Alimentary Canal Organs
Figure 14.3
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Layers of GI tract organs—Inside to Out
 Mucosa
 Submucosa
 Muscularis externa
 Serosa
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Layers of GI tract organs—Inside to Out
 Mucosa —membrane consisting of surface epith.,
CT layer (lamina propria), smooth muscle layer
 Submucosa —soft CT w/ blood vessels & nerve
endings
 Muscularis externa —smooth muscle,inner
circular & outer longitudinal layer
 Serosa —Visceral peritoneum—continuous with
parietal peritoneum that lines the abdominopelvic
cavity
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Secretions
 Saliva —from salivary glands, into pharynx
 Gastric fluid —from stomach, into stomach
 Pancreatic secretions —from pancreas, into small
intestine
 Bile —from liver, stored in gall bladder, into small
intestine.
 …and mucus.
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Glands
Salivary glands
 3 pairs, sublingual, submandibular, parotid
 Secrete watery saliva—with salivary amylase and
mucus
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Glands
Mucus glands
 All parts of GI tract
 Mucus lubricates a bolus of food
 Mucus will be digested and recycled
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Glands
Gastric glands
 In stomach
a) Goblet cells make mucus
b) Parietal cells make hydrochloric acid
c) Chief cells make digestive enzymes, mainly
for protein digestion
 Secretions controlled by ANS and hormones of
stomach
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Glands
Pancreas
 Behind stomach
 Digestive part is an exocrine gland
 Duct joins the bile duct to enter SI
 Secretions contain many enzymes and
bicarbonate ions to neutralize stomach acids
 Stimulated by chyme entering SI
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Glands
Pancreas
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Glands
Liver
 Top right quadrant of abdomen
 Largest gland in the body
 Produces bile—bile salts, bile pigments (from
RBC destruction), excess ions and cholesterol
(removed from blood)
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Glands
Liver
Gall bladder
Gall bladder
 Under the liver
 Stores bile
Hepatic
duct
Cystic duct
 Duct system shown at
right
Common
Bile duct
Pancreas
Pancreatic
duct
Sphincters
Small intestine
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Glands
Intestinal glands
 Between villi of SI
 AKA Crypts of Lieberkuhn —secrete lots of water
to help absorption of digestion products
 Goblet cells and Brunner’s glands make mucus
 Enzymes are embedded in epithelium— not
secreted into lumen
Why?
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Sphincters
 Lips
 Cardiac sphincter
 Pyloric sphincter
 (ligament of Treitz)
 Ileocecal sphincter
 Internal anal sphincter
 External anal sphincter
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Steps in Chemical digestion
Carbohydrates
 Mouth: Salivary amylase breaks starch into
smaller carbohydrates
 SI: Pancreatic amylase breaks starch into smaller
carbohydrates, mainly disaccharides
 SI: Lactase, maltase, and sucrase break
disaccharides into monosaccharides
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Functions of the Digestive System
Figure 14.13 (1 of 3)
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Steps in Chemical digestion
Proteins
 Stomach: Pepsinogen (inactive)/pepsin (activated
by HCl) clips proteins to smaller amino acid
chains
 SI: Trypsin and chymotrypsin (endopeptidases)
clip proteins to smaller amino acid chains.
Carboxypeptidase (exopeptidases) cuts off
terminal amino acids
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Functions of the Digestive System
Figure 14.13 (2 of 3)
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Steps in Chemical digestion
Lipids
 Stomach: Lipase separates fatty acids from
glycerol
 SI: Pancreatic lipase separates fatty acids from
glycerol, bile emulsifies fatty acids into
chylomicrons
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Functions of the Digestive System
Figure 14.13 (3 of 3)
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Enzymes of digestion
 For carbohydrates
Salivary amylase
Pancreatic amylase
Lactase
Maltase
Sucrase
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Enzymes of digestion
 For proteins
Pepsinogen (inactive)
Pepsin (activated by HCl)
Trypsin
Chymotrypsin
Carboxypeptidase
Please note the distinction:
Exopeptidase vs Endopeptidase
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Enzymes of digestion
 For lipids
Lipase
Pancreatic lipase
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Absorption
Proteins
--as amino acids, into capillaries of villi of small
intestine
--to hepatic portal vein, to liver.
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Absorption
Carbohydrates
--as simple sugars, into capillaries of villi of small
intestine
--to hepatic portal vein, to liver.
(Fiber-cellulose-is not digested or absorbed)
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Absorption
Lipids
--as chylomicrons, into lacteals of villi of small
intestine
--to lymph vessels, eventually back to bloodstream.
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Absorption
Other stuff:
 You can absorb water, alcohol, several drugs in
mouth, esophagus, and stomach
 Large intestine absorbs water, several vitamins
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Review
 A cheeseburger has:
-Fats in the meat, cheese, and mayonnaise
-Protein in the meat and cheese
-Carbohydrates in the bun, tomato, and ketchup
-Fiber in the lettuce, tomato and bun
Describe the digestion of a cheeseburger
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Villus
Goblet cell
Lacteal
Capillary network
Arteriole
Lacteal
Venule
Lymphatic vessel
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Stomach
Esophagus
Cardiac sphincter
Smooth muscle layers
Pyloric sphincter
Duodenum
Rugae
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Pancreas
Bile duct
Pancreas
Duodenum
Common bile duct
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Liver
Liver
Gall Bladder
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Aorta
Transverse colon
Ascending colon
Descending
colon
Iliocecal
sphincter
Cecum
Appendix
Sigmoid colon
Rectum
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Esophagus Anatomy and Physiology
 ~10 inches long
 Pharynx  stomach (through diaphragm)
 Moves food by peristalsis
 Passageway for food only (not resp. system)
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Stomach Anatomy
Figure 14.4a
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Stomach –Left upper quadrant
 Regions:
 Cardiac region—(near the heart) Food enters at the
cardiac sphincter
 Fundus
 Body
 Pylorus— Food empties into SI at the pyloric
sphincter
 Rugae—internal folds of the mucosa
 External regions:
 Lesser curvature—medial
 Greater curvature—lateral
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Stomach Anatomy
Figure 14.4a
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Stomach Anatomy
Figure 14.4b
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Stomach Anatomy
 Peritoneum attached to stomach (AKA mesentery)
 Lesser omentum—attaches liver to lesser
curvature
 Greater omentum—attaches greater curvature
to posterior body wall
 Contains fat to insulate, cushion, and
protect abdominal organs
 Has lymph nodules with macrophages
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Stomach Anatomy
Figure 14.5a
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Stomach Anatomy
Figure 14.5b
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Structure of the Stomach Mucosa
Simple columnar ET has:
 Mucous neck cells— produce alkaline mucus
 Gastric glands—in gastric pits, secrete gastric juice
 Chief cells, Parietal cells, Goblet cells
 Enteroendocrine cells —produce gastrin (a
hormone)
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Structure of the Stomach Mucosa
Figure 14.4c
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Structure of the Stomach Mucosa
Figure 14.4d
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Small Intestine—SI
 Primary digestive organ--site of absorption into blood
 Extends from pyloric sphincterileocecal valve
 Suspended from posterior abdominal wall by mesentery
 Ligament of Treitz acts as an external sphincter / oneway valve

Duodenum-Jejunum-Ileum
To increase
surface
area Microvilli—tiny projections of the plasma

membrane (create a brush border appearance)
 Villi—fingerlike structures formed by the mucosa
 Plicae circulares-deep folds of mucosa & submucosa
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Chemical Digestion in the SI
Figure 14.6
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Small Intestine Anatomy
Figure 14.7a
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Small Intestine Anatomy
Figure 14.7b
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Small Intestine Anatomy
Figure 14.7c
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Large Intestine
Larger in diameter, shorter in length, than SI
 Cecum—saclike first part (Appendix attached here)
 Colon
 Ascending—travels up right side
 Transverse—travels across top of abdominal cavity
 Descending—travels down the left
 Sigmoid—enters the pelvis
 Rectum and anal canal—also in pelvis
Internal anal sphincter—involuntary (smooth muscle)
External anal sphincter—voluntary
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Large Intestine
Figure 14.8
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Large Intestine Anatomy
 No villi
 Goblet cells produce alkaline mucus--lubricates
passage of feces
 Muscularis externa layer = three bands of muscle
called teniae coli, cause the wall to pucker into
haustra (pocketlike sacs)
 Gut bacteria make vitamin K and B12
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Control of Digestion
 Hormonal
 CCK, gastrin, secretin
 Neural
 ANS (parasympathetic) through vagus n.
 Chemical
 pH receptors
 Physical
 Stretch receptors
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Pathology
 Food allergies
 Cancer
 Hepatitis
 Ulcers
 Spastic colon
 Cirrhosis
 Diverticulosis
 Dental caries
 Peritonitis
 Scurvy
 Diarrhea /
constipation
 Crohn’s disease
 Kwashiorkor
 Hemorrhoids
 Lactose
intolerance
 Cholecystitis
 Appendicitis
 Heartburn
 Nausea/ Dyspepsia
 Hernia
 Pancreatitis
 Morbid obesity
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Why “Supersize” Means Expanding Waistlines
Whether they're called "value meals" or "mega
meals," whether they're "supersize" or "kingsize," fast-food portions are notoriously high in
fat and calories.
Now, in a recent study published in the American
Journal of Public Health, researchers confirm
that fast-food portion sizes have increased in
recent years and indicate that they may be a
major cause of obesity in the United States…
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…in a study conducted by researchers at
Tufts University […] to compare the
effectiveness of four popular diet
programs. The researchers who led the
study found that the four diets were
equally effective in those who stayed on
them […] more than half of the subjects on
each diet dropped out before the one-year
study period was completed
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…from recent searches
Results 1 - 50 of about 91,400,000 for
weight loss
Results 1 - 50 of about 17,000,000 for
weight loss diet
Results 1 - 50 of about 4,740,000 for
dangerous diet
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Nutrition
 Nutrient—
.
 Major nutrients
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 Minor nutrients
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Nutrition
 Nutrient—substance used by the body for growth,
maintenance, and repair
 Major nutrient
 Carbohydrates
 Lipids
 Proteins
 Water
 Minor nutrients
 Vitamins
A, D, E, and K
are the fat-soluble
vitamins
 Minerals
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The old food pyramid
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Five Basic Food Groups and
Some of Their Major Nutrients
Table 14.2 (1 of 2)
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Five Basic Food Groups and
Some of Their Major Nutrients
Table 14.2 (2 of 2)
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USDA Food Guide Pyramid
Figure 14.17
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Dietary Sources of Major Nutrients
 Carbohydrates
 Lipids:
 Proteins
 Vitamins
 Minerals
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Dietary Sources of Major Nutrients
 Carbohydrates mainly from plants
 Lipids: meats,
seeds,
animal products
(saturated fats) (unsaturated fats) (cholesterol)
 Proteins--animal products, legumes, beans
 Vitamins--all major food groups
 Minerals-vegetables, legumes, milk, some meats
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Today the average person gets two-thirds of
his daily calories from just four species:
corn, soybeans, wheat and rice. That can't
be optimal…
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Recommendations
 Eat food. Not too much. Mostly plants
 A little meat won’t kill you, though it’s better
approached as a side dish than as a main. And
you’re much better off eating whole fresh foods
than processed food products. That’s what I mean
by the recommendation to eat “food.” Once, food
was all you could eat, but today there are lots of
other edible foodlike substances in the
supermarket.
--M Pollan, NYT, 2007
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