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Chapter 3

HN 196 Chapter Notes - Chapter 3: Jejunum, Autonomic Nervous System, Central Nervous System


Department
Human Nutrition
Course Code
HN 196
Professor
Braunschweig
Chapter
3

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Nutrition 196 The Digestive System
Digestion
- Begins in the mouth
o Chewing is the mechanical digestion that breaks food into smaller pieces
o Some chemical digestion takes place in the mouth
Salivary amylase: an enzyme produced by the salivary glands that begins the
chemical digestion of carbohydrates
o The esophagus propels food into the stomach
The epiglottis covers the opening to the trachea during swallowing
Food travels from the mouth to the stomach through the esophagus
Peristalsis is the muscular contractions moving food through the GI tract
The Gastrointestinal Sphincter separates the esophagus from the stomach
- Goes to the stomach
o The stomach mixes, digests,
and stores food
o Digestion in the stomach
includes
Extensive
mechanical digestion
to mix food with
gastric juice
Chemical digestion
of proteins and fats
o Gastric juice contains:
Hydrochloric acid: to
denature proteins
and activate pepsin
Intrinsic factor: a
protein critical to the
absorption of
vitamin b12
Pepsin: an enzyme
to digest protein
Gastric lipase: an
enzyme to digest fat
o Chyme: semisolid product of
mechanical and chemical
digestion in the stomach
- Goes to the small intestine
o From stomach, chyme is
slowly released through the pyloric sphincter to the small intestine
o Chemical digestion continues in the small intestine using pancreatic enzymes and
bile
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