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Digestive System Chapter 14
ACCESSORY ORGANS:
ORGANS:
Mouth
• Teeth chew food
• Tongue positions and
tastes food
Salivary glands
• Saliva moistens food
• Bicarbonate maintains pH
• Amylase digests starch
• Lysozyme inhibits bacteria
Liver
• Produces bile
• Performs various functions
associated with processing
and storing nutrients
Gallbladder
• Stores and concentrates bile
Pancreas
• Secretes digestive enzymes
into small intestine
• Secretes bicarbonate into
small intestine to neutralize
stomach acid
Appendix
• No known digestive function
Pharynx
• Passageway for food and air
• Participates in swallowing
Esophagus
• Moves food from pharynx
to stomach
Stomach
• Stores and mixes food
• Begins chemical digestion of
protein by enzymes and acid
• Regulates delivery to the
small intestine
Small intestine
• Digests proteins, fats,
and carbohydrates
• Absorbs most of the water
and nutrients
• Secretes digestive hormones
and enzymes
Large intestine
• Absorbs the last of the water
and nutrients
• Stores waste material
Sigmoid colon
• Stores feces
Rectum
• Passageway for feces
Anus
• Expels undigested material
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Figure 14.1
Gastrointestinal (GI) Tract Wall
Vein
Artery
Nerve
Lymph vessel
Serosa
• Connective tissue
outer covering
• Protects and anchors
the digestive tract
Longitudinal
layer
Circular
layer
Lumen
Mucosa
• Mucous membrane layer
• Lines the digestive tract
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Muscularis
• Two layers of smooth muscle
• Responsible for motility of the
digestive tract
Submucosa
• Connective tissue layer
• Contains blood vessels, lymph vessels,
and nerves
Figure 14.2
Motility: Peristalsis
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Figure 14.3a
Motility: Segmentation
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Figure 14.3b
Salivary Glands
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Figure 14.5
Swallowing
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Figure 14.6a
Swallowing
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Figure 14.6b
Structure of the Stomach Wall
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Figure 14.7a–b
Stomach Function
 Specific cells secrete gastric juice
 Hydrochloric acid
 Produces a pH of about 2; breaks down
large bits of food
 Mucus
 Protects stomach lining from acid
 Pepsinogen
 With acid, begins protein breakdown as
pepsin
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The Stomach
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Figure 14.7
Peristalsis
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Figure 14.8
Small Intestine
 Functions
 Digestion
 Neutralizes acid from stomach
 Adds digestive enzymes and bile
 Breaks proteins, carbohydrates, and lipids
to absorbable materials
 Absorption
 95% of food absorbed in small intestine
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Small Intestine
 Structure
 Regions
 Duodenum
 Jejunum
 Ileum
 Mucosa adaptations
 Villi containing blood and lacteal
capillaries
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The Wall of the Small Intestine
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Figure 14.9a–b
The Wall of the Small Intestine
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Figure 14.9c
Major Digestive Enzymes
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Table 14.1
Accessory Organs: Aid Digestion and
Absorption
Liver
• Produces bile
(water and electrolytes,
cholesterol, bile salts,
lecithin, and
pigments)
Esophagus
Stomach
Common
bile duct
Gallbladder
• Stores and
concentrates bile
• Delivers bile to the
duodenum via the
common bile duct
Duodenum
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Pancreatic duct
Pancreas
• Secretes enzymes
(proteases, amylase,
lipase)
• Produces sodium
bicarbonate
• Delivers these products to
the duodenum via ducts
Figure 14.10
Accessory Organs: Aid Digestion and
Absorption
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Figure 14.11
Large Intestine
Transverse
colon
Ascending
colon
Descending
colon
Small
intestine
Ileocecal
valve
Cecum
Appendix
Sigmoid colon
Rectum
Internal anal
sphincter
(smooth muscle)
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External anal
sphincter
(skeletal muscle)
Anus
Anal canal
Figure 14.12
Absorption of Proteins and Carbohydrates
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Figure 14.13
Endocrine and Nervous Systems Regulation
of Digestion
 Regulation dependent on volume and
content of food
 Nervous system
 Stretch receptors in stomach
 Hormones
 Gastrin
 Secretin
 Cholecystokinin (CCK)
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Absorption of Fats
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Figure 14.14
Nutrients: Utilized or Stored Until Needed
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Figure 14.15
Food Guide Pyramid
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Figure 14.16
Disorders of the Digestive System
 Disorders of the GI tract
 Lactose intolerance
 Diverticulosis
 Colon polyps
 Disorders of accessory organs
 Hepatitis
 Gallstones
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Disorders of the Digestive System
 Malnutrition
 Obesity
 Eating disorders
 Anorexia nervosa
 Bulimia
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