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Chapter 25,26,27
Digestion and Nutrition
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General
Characteristics of
the Alimentary
Canal
• Approximately 27 feet
• Structure of the wall – 4
layers
–
–
–
–
Mucosa - protects
Submucosa- nourishes
Muscular – propel food
Serosa - secretes serous
fluid – lubrication
• Movements of the tube
(peristalsis)
– Mixing
– Propelling
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Peristalsis
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Mouth - oral cavity
• Cheeks and lips
• Tongue – held down by frenulum
• Palate
– Hard palate
– Soft palate
• Teeth
– Primary
– Secondary
– Incisors, cuspids, bucuspids, molars
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teeth
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Salivary Glands
• Salivary secretions
– Serous cells
– Amylase - digests carbohydrates
– mucous
• Major salivary glands
– Parotid
– Submandibular
– Sublingual
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Salivary glands
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pharynx
• Structure
– Nasopharynx
– Oropharynx
– Laryngopharynx
• Swallowing mechanism
– Food mixed and forced into pharynx
– Sensory receptors trigger swallowing reflex
– peristalsis
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Esophagus
• Collapsible passageway leading to stomach
• Mucous glands
• Esophageal sphincter
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The stomach
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Stomach
• Parts of the stomach
– Cardiac, fundic, body, pyloric
– Pyloric sphincter
• Gastric secretions - mucus, pepsin, hydrochloric
acids, intrinsic factor
• Regulation of gastric secretions
– Parasympathetic impulses, gastrin (increases
secretions of gastric glands
• Gastric absorption
• Mixing and emptying actions (chyme)
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pancreas
• Produces pancreatic juices which aid in
digestion
• Located in association with the small
intestine
• Structure of the pancreas
– Acinar cells – produce pancreatic juices.
– Travel through Pancreatic duct
– Controlled by Hepatopancreatic sphincter
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• Pancreatic juice
– Digest organic compounds
– Amylase, lipase, chymotrypsin (trypsin),
carboxypeptidase, nucleases
• Regulation of pancreatic secretions
– Secretin - stimulates release of pancreatic fluid
– cholecystokinin
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The Pancreas
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The liver
• Location
• Structure
– Hepatic lobules, sinusoids
– Hepatic portal vein
– Kupfer cells
• Function - metabolism of glucose from
noncarbohydrates, storage of vitamin D,
filter blood, digestion
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Bile
•
•
•
•
Functions of bile salts-emulsify fat
Made in liver
Gallbladder - stores bile
Composition of bile- water, bile salts, bile
pigments, cholesterol, electrolytes
• Regulation of bile release cholecystokinin, hepatopancreatic
sphincter
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Small Intestine
• Function
– Receives pancreas and liver secretion, completes digestion of nutrients, absorbs
products of digestion, transports residues to large intestine.
• Parts of the small intestine
– Duodenum, jejunum, ileum
– Duodenum – shortest, fixed portion
– Suspended by mesentery
• Small intestinal wall
– Lined with villi – connective tissue and capillaries
– 4 layers
• Secretions
– Goblet cells – secrete mucous
– Intestinal gland – watery fluid
– Digestive enzymes
• Regulation of secretion – mechanical and chemical stimulation –
release of mucous
• Absorption of nutrients
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Large intestine
• Parts – ascending colon, transverse colon,
descending colon
• Structure of wall
– 4 layers
– No villi
• Functions - reabsorption of water from chyme
• Movements accomplished by peristalsis
• Feces – waste products
– Contain undigested material, mucous, water, bacteria
– Color – bile salts
– Smell – bacterial action
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Nutrition and Nutrients
A. Nutrition is the process by which the body
takes in and uses nutrients.
B. Essential nutrients are those that cannot be
synthesized by human cells.
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Carbohydrates
• Sources
• Utilization
• requirements
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Lipids
• Sources
• Utilization
• Requirements
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proteins
• Sources
• requirements
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vitamins
• Fat soluble
• Water soluble
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minerals
• Characteristics
• Major minerals
• Trace elements
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