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Chapter 14
The Digestive
System and Body
Metabolism
Lecture Presentation by
Patty Bostwick-Taylor
Florence-Darlington Technical College
© 2015 Pearson Education, Inc.
The Digestive System Functions
 Ingestion—taking in food
 Digestion—breaking food into nutrient molecules
 Absorption—movement of nutrients into the
bloodstream
 Defecation—elimination of indigestible waste
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Organs of the Digestive System
 Two main groups of organs
 Alimentary canal (gastrointestinal or GI tract)—
performs the whole menu of digestive functions as it
propels the foodstuffs along its tract
 These organs ingest, digest, absorb, defecate
 Accessory digestive organs- Assist the process of
digestive breakdown in various ways.
 Includes teeth, tongue, and other large digestive
organs
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Figure 14.1 The human digestive system: Alimentary canal and accessory organs.
Mouth (oral cavity)
Tongue
Parotid gland
Sublingual gland
Submandibular
gland
Salivary glands
Pharynx
Esophagus
Stomach
Pancreas
(Spleen)
Liver
Gallbladder
Small
intestine
Duodenum
Jejunum
Ileum
Anus
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Transverse colon
Descending colon
Ascending colon
Cecum
Sigmoid colon
Rectum
Appendix
Anal canal
Large intestine
Organs of the Alimentary Canal
 The alimentary canal ( GI Tract) is a continuous,
coiled, hollow tube that runs through the ventral
cavity from stomach to anus:
 Mouth
 Pharynx
 Esophagus
 Stomach
 Small intestine
 Large intestine
 Anus ( the terminal opening of the large intestine)
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Mouth (Oral Cavity)
 Anatomy of the mouth
 The mouth (oral cavity)—mucous membrane–lined
cavity
 Lips (labia)—protect the anterior opening
 Cheeks—form the lateral walls
 Hard palate—forms the anterior roof
 Soft palate—forms the posterior roof
 Uvula—fleshy projection of the soft palate
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Mouth (Oral Cavity)
 Anatomy of the mouth (continued)
 Vestibule—space between lips externally and teeth
and gums internally
 Oral cavity proper—area contained by the teeth
 Tongue—attached at hyoid bone and styloid
processes of the skull, and by the lingual frenulum to
the floor of the mouth
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Mouth (Oral Cavity)
 Anatomy of the mouth (continued)
 Tonsils
 Palatine—located at posterior end of oral cavity
 Lingual—located at the base of the tongue
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Figure 14.2a Anatomy of the mouth (oral cavity).
Nasopharynx
Hard
palate
Oral
cavity
Soft palate
Lips (labia)
Palatine tonsil
Vestibule
Lingual tonsil
Lingual
frenulum
Tongue
Hyoid bone
Trachea
(a)
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Uvula
Oropharynx
Epiglottis
Laryngopharynx
Esophagus
Figure 14.2b Anatomy of the mouth (oral cavity).
Upper lip
Gingivae
(gums)
Hard palate
Soft palate
Uvula
Palatine tonsil
Oropharynx
Tongue
(b)
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Mouth
 Functions of the mouth
 Mastication (chewing) of food
 Tongue mixes masticated food with saliva
 Tongue initiates swallowing
 Taste buds on the tongue allow for taste
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Pharynx
 Food passes from the mouth posteriorly into the:
 Oropharynx—posterior to oral cavity
 Laryngopharynx—below the oropharynx and
continuous with the esophagus
The pharynx serves as a passageway for food, fluids,
and air
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Esophagus (Gullet)
 Anatomy
 About 10 inches long
 Runs from pharynx to stomach through the
diaphragm
 Physiology
 Conducts food by peristalsis (slow rhythmic
squeezing) to the stomach
 Passageway for food only
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Stomach
 The stomach is a C-shaped organ located on the
left side of the abdominal cavity
 Food enters at the cardioesophageal sphincter from
the esophagus
 Food empties into the small intestine at the pyloric
sphincter (valve)
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Stomach
 Regions of the stomach
 Cardial part (cardia)—near the heart
 Fundus—expanded portion lateral to the cardiac
region
 Body—midportion
 Pylorus—funnel-shaped terminal end
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Stomach
 Stomach can stretch and hold 4 L (1 gallon) of food
when full
 Rugae—internal folds of the mucosa present when
the stomach is empty
 External regions
 Lesser curvature—concave medial surface
 Greater curvature—convex lateral surface
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Figure 14.4a Anatomy of the stomach.
Cardia
Fundus
Esophagus
Muscularis
externa
• Longitudinal layer
• Circular layer
• Oblique layer
Pylorus
Serosa
Body
Lesser
curvature
Rugae
of mucosa
Greater
curvature
Duodenum
(a)
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Pyloric
sphincter
(valve)
Pyloric
antrum
Figure 14.4b Anatomy of the stomach.
Fundus
Body
Rugae
of mucosa
(b)
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Pyloric
sphincter
Pyloric
antrum
Stomach
 Functions of the stomach
 Temporary storage tank for food
 Site of food breakdown
 Chemical breakdown of protein begins
 Delivers chyme (processed food) to the small
intestine
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Small Intestine
 The body’s major digestive organ
 Chemical digestion begins in the small intestine
 Longest portion of the alimentary tube (2–4 m or
7–13 feet in a living person)
 Site of nutrient absorption into the blood
 Muscular tube extending from the pyloric sphincter
to the ileocecal valve
 Suspended from the posterior abdominal wall
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Figure 14.5 Peritoneal attachments of the abdominal organs.
Diaphragm
Falciform ligament
Liver
Spleen
Gallbladder
Stomach
Visceral peritoneum
Greater omentum
Lesser
omentum
Pancreas
Duodenum
Transverse
colon
Mesenteries
Parietal peritoneum
Small intestine
Peritoneal
cavity
Uterus
Large intestine
Cecum
Rectum
Anus
Urinary bladder
(a)
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(b)
Small Intestine
 Subdivisions
 Duodenum
 Attached to the stomach
 Curves around the head of the pancreas
 Jejunum
 Attaches anteriorly to the duodenum
 Ileum
 Extends from jejunum to large intestine
 Meets the large intestine at the ileocecal valve
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Large Intestine
 Larger in diameter, but shorter in length at 1.5 m,
than the small intestine
 Extends from the ileocecal valve to the anus
 Subdivisions:
 Cecum
 Appendix
 Colon
 Rectum
 Anal canal
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Large Intestine Anatomy
 Cecum—saclike first part of the large intestine
 Appendix
 Accumulation of lymphoid tissue that sometimes
becomes inflamed (appendicitis)
 Hangs from the cecum
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Large Intestine Anatomy
 Colon
 Ascending—travels up right side of abdomen
 Transverse—travels across the abdominal cavity
 Descending—travels down the left side
 Sigmoid—S-shaped region; enters the pelvis
 Sigmoid colon, rectum, and anal canal are located
in the pelvis
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Large Intestine Anatomy
 Anal canal ends at the anus
 Anus—opening of the large intestine
 The large intestine delivers undigestible food
residues to the body’s exterior
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Figure 14.8 The large intestine.
Left colic
(splenic) flexure
Transverse
mesocolon
Right colic
(hepatic) flexure
Transverse
colon
Haustrum
Descending
colon
Ascending colon
Cut edge of
mesentery
Ileum (cut)
Ileocecal valve
Teniae coli
Sigmoid
colon
Cecum
Appendix
Rectum
Anal canal
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External anal sphincter
Accessory Digestive Organs
 Teeth
 Salivary glands
 Pancreas
 Liver
 Gallbladder
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Teeth
 Teeth masticate (chew) food into smaller fragments
 Humans have two sets of teeth during a lifetime:
1. Deciduous (also known as baby or “milk”) teeth
 A baby has 20 teeth by age 2
 First teeth to appear are the lower central incisors
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Teeth
2. Permanent teeth
 Replace deciduous teeth between the ages of 6 and
12
 A full set is 32 teeth, but some people do not have
wisdom teeth
 If they do emerge, the wisdom teeth appear between
ages of 17 and 25
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Classification of Teeth
 Incisors—cutting
 Canines (eyeteeth)—tearing or piercing
 Premolars (bicuspids)—grinding
 Molars—grinding
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Figure 14.9 Human deciduous and permanent teeth.
Incisors
Central
(6–8 mo)
Lateral
(8–10 mo)
Canine (eyetooth)
(16–20 mo)
Molars
First molar
(10–15 mo)
Second molar
(about 2 yr)
Incisors
Central (7 yr)
Lateral (8 yr)
Canine (eyetooth)
(11 yr)
Premolars
(bicuspids)
First premolar
(11 yr)
Second premolar
(12–13 yr)
Molars
First molar
(6–7 yr)
Second molar
(12–13 yr)
Third molar
(wisdom tooth)
(17–25 yr)
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Deciduous
(milk) teeth
Permanent
teeth
Regions of a Tooth
 Two major regions of a tooth
1. Crown-exposed part of tooth above the gum
 Note: The neck is a connector between the crown
and root.
 Region in contact with the gum
 Connects crown to root
2. Root- embedded in the maxilla or the mandible and
are covered by gums
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Figure 14.10 Longitudinal section of a molar.
Enamel
Dentin
Crown
Neck
Pulp cavity
(contains
blood vessels
and nerves)
Gum
(gingiva)
Cement
Root
Root canal
Periodontal
membrane
(ligament)
Bone
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Salivary Glands
 Three pairs of salivary glands empty secretions into
the mouth
1. Parotid glands
 Found anterior to the ears
2. Submandibular glands
3. Sublingual glands
 Both submandibular and sublingual glands empty
saliva into the floor of the mouth through small ducts
© 2015 Pearson Education, Inc.
Figure 14.1 The human digestive system: Alimentary canal and accessory organs.
Mouth (oral cavity)
Tongue
Parotid gland
Sublingual gland
Submandibular
gland
Salivary glands
Pharynx
Esophagus
Stomach
Pancreas
(Spleen)
Liver
Gallbladder
Small
intestine
Duodenum
Jejunum
Ileum
Anus
© 2015 Pearson Education, Inc.
Transverse colon
Descending colon
Ascending colon
Cecum
Sigmoid colon
Rectum
Appendix
Anal canal
Large intestine
Salivary Glands
 Saliva
 Mixture of mucus and serous fluids
 Helps to moisten and bind food together into a mass
called a bolus
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Pancreas
 Soft, pink, triangular gland that extends across the
abdomen from spleen to duodenum
 Produces a wide spectrum of digestive enzymes
that break down all categories of food
 Secretes enzymes into the duodenum
 Hormones produced by the pancreas
 Insulin
 Glucagon
© 2015 Pearson Education, Inc.
Figure 14.1 The human digestive system: Alimentary canal and accessory organs.
Mouth (oral cavity)
Tongue
Parotid gland
Sublingual gland
Submandibular
gland
Salivary glands
Pharynx
Esophagus
Stomach
Pancreas
(Spleen)
Liver
Gallbladder
Small
intestine
Duodenum
Jejunum
Ileum
Anus
© 2015 Pearson Education, Inc.
Transverse colon
Descending colon
Ascending colon
Cecum
Sigmoid colon
Rectum
Appendix
Anal canal
Large intestine
Figure 14.6 The duodenum of the small intestine and related organs.
Right and left
hepatic ducts
from liver
Cystic duct
Common hepatic duct
Bile duct and sphincter
Accessory pancreatic duct
Pancreas
Gallbladder
Jejunum
Duodenal
papilla
Hepatopancreatic
ampulla and sphincter
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Main pancreatic duct and sphincter
Duodenum
Liver
 Largest gland in the body
 Located on the right side of the body under the
diaphragm
 Consists of four lobes suspended from the
diaphragm and abdominal wall
 Connected to the gallbladder via the common
hepatic duct
© 2015 Pearson Education, Inc.
Figure 14.1 The human digestive system: Alimentary canal and accessory organs.
Mouth (oral cavity)
Tongue
Parotid gland
Sublingual gland
Submandibular
gland
Salivary glands
Pharynx
Esophagus
Stomach
Pancreas
(Spleen)
Liver
Gallbladder
Small
intestine
Duodenum
Jejunum
Ileum
Anus
© 2015 Pearson Education, Inc.
Transverse colon
Descending colon
Ascending colon
Cecum
Sigmoid colon
Rectum
Appendix
Anal canal
Large intestine
Liver
 Bile is produced by cells in the liver
 Bile leaves the liver through the common hepatic
duct and enters duodenum through the bile duct
 Bile is a yellow-green, watery solution that helps
with digestion.
 Breaks down fats into fatty acid.
 Contains water, body salts (potassium and sodium)
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Gallbladder
 Sac found in shallow fossa of liver
 When no digestion is occurring, bile backs up the
cystic duct for storage in the gallbladder
 Gallstones are crystallized cholesterol, which can
cause blockages
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Figure 14.1 The human digestive system: Alimentary canal and accessory organs.
Mouth (oral cavity)
Tongue
Parotid gland
Sublingual gland
Submandibular
gland
Salivary glands
Pharynx
Esophagus
Stomach
Pancreas
(Spleen)
Liver
Gallbladder
Small
intestine
Duodenum
Jejunum
Ileum
Anus
© 2015 Pearson Education, Inc.
Transverse colon
Descending colon
Ascending colon
Cecum
Sigmoid colon
Rectum
Appendix
Anal canal
Large intestine
Figure 14.6 The duodenum of the small intestine and related organs.
Right and left
hepatic ducts
from liver
Cystic duct
Common hepatic duct
Bile duct and sphincter
Accessory pancreatic duct
Pancreas
Gallbladder
Jejunum
Duodenal
papilla
Hepatopancreatic
ampulla and sphincter
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Main pancreatic duct and sphincter
Duodenum
Functions of the Digestive System
 Major functions of the digestive system are
summarized as:
 Digestion
 Absorption
 We will cover 6 more specific processes next
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Functions of the Digestive System
1. Ingestion—placing of food into the mouth
2. Propulsion—movement of foods from one region
of the digestive system to another
 Peristalsis—alternating waves of contraction and
relaxation that squeezes food along the GI tract
 Segmentation—movement of materials back and
forth to foster mixing in the small intestine
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Functions of the Digestive System
3. Food breakdown: mechanical breakdown
 Examples:
 Mixing of food in the mouth by the tongue
 Churning of food in the stomach
 Segmentation in the small intestine
 Mechanical digestion prepares food for further
degradation by enzymes
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Functions of the Digestive System
4. Food breakdown: digestion
 Digestion occurs when enzymes chemically break
down large molecules into their building blocks
 Each major food group uses different enzymes
 Carbohydrates are broken to monosaccharides
(simple sugars)
 Proteins are broken to amino acids
 Fats are broken to fatty acids
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Functions of the Digestive System
5. Absorption
 End products of digestion are absorbed in the blood
or lymph
 Food must enter mucosal cells and then into blood or
lymph capillaries
6. Defecation
 Elimination of indigestible substances from the GI
tract in the form of feces
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Figure 14.11 Schematic summary of gastrointestinal tract activities.
Ingestion
Mechanical
breakdown
• Chewing (mouth)
• Churning (stomach)
• Segmentation
(small intestine)
Digestion
Food
Pharynx
Esophagus
Propulsion
• Swallowing
(oropharynx)
• Peristalsis
(esophagus, stomach,
small intestine, large
intestine)
Stomach
Absorption
Lymph vessel
Small intestine
Blood vessel
Large intestine
Mainly H2O
Feces
Defecation
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Anus
Activities Occurring in the Mouth, Pharynx,
and Esophagus
 Food ingestion and breakdown
 Food is placed into the mouth
 Physically broken down by chewing
 Mixed with saliva
 Essentially, no food absorption occurs in the mouth
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Activities Occurring in the Mouth, Pharynx,
and Esophagus
 Food propulsion—swallowing and peristalsis
 Pharynx and esophagus have no digestive function
 Serve as passageways to the stomach
 Pharynx functions in swallowing
 Two phases of swallowing:
1. Buccal phase
2. Pharyngeal-esophageal phase
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Activities Occurring in the Mouth, Pharynx,
and Esophagus
 Food propulsion—swallowing and peristalsis
(continued)
1. Buccal phase
 Voluntary
 Occurs in the mouth
 Food is formed into a bolus
 The bolus is forced into the pharynx by the tongue
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Activities Occurring in the Mouth, Pharynx,
and Esophagus
 Food propulsion—swallowing and peristalsis
(continued)
2. Pharyngeal-esophogeal phase (continued)
 Involuntary transport of the bolus by peristalsis
 Peristalsis moves the bolus toward the stomach
 The cardioesophageal sphincter is opened when food
presses against it
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Figure 14.14a Swallowing.
Bolus of food
Tongue
Pharynx
Upper
Epiglottis
esophageal
up
sphincter
Glottis (lumen)
of larynx
Esophagus
Trachea
(a) Upper esophageal
sphincter contracted
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Figure 14.14b Swallowing.
Uvula
Bolus
Epiglottis
down
Larynx up
Esophagus
(b) Upper esophageal
sphincter relaxed
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Figure 14.14c Swallowing.
Bolus
(c) Upper esophageal
sphincter contracted
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Figure 14.14d Swallowing.
Relaxed muscles
Cardioesophageal
sphincter open
(d) Cardioesophageal
sphincter relaxed
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Activities in the Stomach
 Food breakdown
 Food propulsion
1. Peristalsis: Waves of peristalsis occur from the
fundus to the pylorus, forcing food past the pyloric
sphincter
2. Grinding: The pylorus meters out chyme into the
small intestine (3 ml at a time)
3. Retropulsion: Peristaltic waves close the pyloric
sphincter, forcing content back into the stomach.
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Figure 14.15 Peristaltic waves in the stomach.
Pyloric
valve
closed
Pyloric
valve
slightly
opened
1 Propulsion: Peristaltic
waves move from the
fundus toward the pylorus.
2 Grinding: The most
vigorous peristalsis and
mixing action occur close to
the pylorus. The pyloric end
of the stomach acts as a
pump that delivers small
amounts of chyme into the
duodenum.
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Pyloric
valve
closed
3 Retropulsion: The
peristaltic wave closes the
pyloric valve, forcing most of
the contents of the pylorus
backward into the stomach.
Activities of the Small Intestine
 Food breakdown and absorption
 Intestinal enzymes function to:
 Break double sugars into simple sugars
 Complete some protein digestion
 Pancreatic enzymes play the major role in the
digestion of fats, proteins, and carbohydrates
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Activities of the Large Intestine
 Food breakdown and absorption
 Remaining materials are eliminated via feces
 Feces contains:
 Undigested food residues
 Mucus
 Bacteria
 Water
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POP QUIZ
 What happen during buccal stage of swallowing?
 How does segmentation differ from peristalsis in terms
of moving substances along the GI tract?
 What does it mean when we say that food “went down
the wrong tube”?
 Differentiate between mechanical and chemical
breakdown?
 What is the name of the end part of the stomach that
connect to the small intestine.
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Nutrition and Metabolism
 Most foods are used as metabolic fuel
 Foods are oxidized and transformed into adenosine
triphosphate (ATP)
 ATP is chemical energy that drives cellular activities
 Energy value of food is measured in kilocalories
(kcal) or Calories (C)
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Nutrition
 Nutrient—substance used by the body for growth,
maintenance, and repair
 Major nutrients
 Carbohydrates
 Lipids
 Proteins
 Water
 Minor nutrients
 Vitamins
 Minerals
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Figure 14.17 Two visual food guides.
White rice, white bread,
potatoes, pasta, sweets:
use sparingly
Dairy or calcium
supplement: 1–2 servings
Red meat, butter:
use sparingly
Fish, poultry, eggs:
0–2 servings
Nuts, legumes:
1–3 servings
Fruits:
2–3 servings
Vegetables
in abundance
Whole-grain
foods at
most meals
Plant oils at
most meals
Daily exercise and weight control
(a) Healthy Eating Pyramid
(b) USDA’s MyPlate
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Nutrition
 A diet consisting of foods from the five food groups
normally guarantees adequate amounts of all the
needed nutrients
 The five food groups are summarized next in Table
14.2
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Table 14.2 Five Basic Food Groups and Some of Their Major Nutrients (1 of 2).
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Table 14.2 Five Basic Food Groups and Some of Their Major Nutrients (2 of 2).
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Dietary Sources of Major Nutrients
 Carbohydrates
 Dietary carbohydrates are sugars and starches
 Most are derived from fruits, grains, vegetables and
milk products
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Dietary Sources of Major Nutrients
 Lipids
 Saturated fats from animal products (meats)
 Unsaturated fats from nuts, seeds, and vegetable
oils
 Cholesterol from egg yolk, meats, and milk products
(dairy products)
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Dietary Sources of Major Nutrients
 Proteins
 Complete proteins—contain all essential amino acids
 Most are from animal products (eggs, milk, meat,
poultry, and fish)
 Essential amino acids: those that the body cannot
make and must be obtained through diet
 Beans also have proteins, but the proteins are
incomplete
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Dietary Sources of Major Nutrients
 Vitamins
 Organic nutrients of various forms that the body
requires in small amounts
 Found mainly in fruits and vegetables
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Dietary Sources of Major Nutrients
 Minerals
 Mainly important for enzyme activity
 Foods richest in minerals: vegetables, milk, and
some meats
 Iron is important for making hemoglobin
 Calcium is important for building bone, blood clotting,
and secretory activities
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Do Now
 What is the name of the rhythmic contractions in the
esophagus?
 Identify the three types of teeth present in your
mouth and the function of each type.
 List the six nutrient categories
 Define nutrient and kilocalories
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Metabolism
 Metabolism is all of the chemical reactions
necessary to maintain life
 Catabolism—the breakdown of molecules to
obtain energy
 Anabolism—larger molecules are built from smaller
ones
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Carbohydrate Metabolism
 Carbohydrates are the body’s preferred source to
produce cellular energy (ATP)
 Glucose (blood sugar)
 Major breakdown product of carbohydrate digestion
 Fuel used to make ATP
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Carbohydrate Metabolism
 Cellular respiration
 As glucose is oxidized, carbon dioxide, water, and
ATP are formed
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Figure 14.19 Summary equation for cellular respiration.
C6H12O6
Glucose
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+
6
O2
Oxygen
gas
6 CO2
Carbon
dioxide
+
6
H2O
Water
+
ATP
Energy
Carbohydrate Metabolism
 Events of three main metabolic pathways of cellular
respiration
1. Glycolysis (2 ATP)
 Occurs in the cytosol
 glucose molecule is split into two pyruvic acid
molecules and produce ATP
2. Krebs cycle (2 ATP)
 Occurs in the mitochondrion
3. Electron transport chain (28 ATP)
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Carbohydrate Metabolism
 Hyperglycemia—excessively high levels of glucose
in the blood
 Excess glucose is stored in body cells as glycogen
or converted to fat
 Hypoglycemia—low levels of glucose in the blood
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Fat Metabolism
 Fats
 Insulate the body
 Protect organs
 Build some cell structures (membranes and myelin
sheaths)
 Provide reserve energy
 Excess dietary fat is stored in subcutaneous tissue
and other fat depots
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Fat Metabolism
 When carbohydrates are in limited supply, more fats
are oxidized to produce ATP
 Excessive fat breakdown causes blood to become
acidic (acidosis or ketoacidosis)
 Breath has a fruity odor
 Common with:
 “No carbohydrate” diets
 Uncontrolled diabetes mellitus
 Starvation
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Protein Metabolism
 Proteins are the main tissue builders in the body
 Ingested proteins are broken down into amino acids
 Amino acids are oxidized to form ATP mainly when
other fuel sources are not available
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The Central Role of the Liver in Metabolism
 Liver is the body’s key metabolic organ
 Roles in digestion:
 Manufactures bile
 Detoxifies drugs and alcohol
 Produces cholesterol, blood proteins (albumin and
clotting proteins)
 Plays a central role in metabolism
 Liver can regenerate if part of it is damaged or
removed
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The Central Role of the Liver in Metabolism
 To maintain homeostasis of blood glucose levels,
the liver performs:
 Glycogenesis—“glycogen formation”
 Glucose molecules are converted to glycogen and
stored in the liver
 Glycogenolysis—“glycogen splitting”
 Glucose is released from the liver after conversion
from glycogen
 Gluconeogenesis—“formation of new sugar”
 Glucose is produced from fats and proteins
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Body Energy Balance
 Energy intake = Total energy output
(heat + work + energy storage)
 Energy intake is the energy liberated during food
oxidation
 Energy produced during glycolysis, Krebs cycle, and
the electron transport chain
 Energy output
 Energy we lose as heat (60%)
 Energy stored as fat or glycogen
 Body weight is usually relatively stable
 Energy intake and output remain about equal
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Body Energy Balance
 Interference with the body’s energy balance leads
to:
 Obesity
 Malnutrition
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Metabolic Rate and Body Heat Production
 Nutrients yield different amounts of energy
 Energy value is measured in kilocalorie (kcal)
 Carbohydrates and proteins yield 4 kcal/gram
 Fats yield 9 kcal/gram
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Basal Metabolic Rate
 Basic metabolic rate (BMR)—amount of heat
produced by the body per unit of time at rest
 Average BMR is about 60 to 72 kcal/hour for an
average 70-kg (154-lb) adult
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Basal Metabolic Rate
 Factors that influence BMR
 Surface area—a small body usually has a higher
BMR
 Gender—males tend to have higher BMRs
 Age—children and adolescents have higher BMRs
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Total Metabolic Rate (TMR)
 TMR—total amount of kilocalories the body must
consume to fuel ongoing activities
 TMR increases dramatically with an increase in
muscle activity
 TMR must equal calories consumed to maintain
homeostasis and maintain a constant weight
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