Download The Digestive System

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The Digestive System
• Ingestion
• Mechanical digestion
• Chemical digestion
• Movements
• Absorption
• Elimination
Pharynx & Esophagus
• Both oropharynx and laryngopharynx
• Esophagus
Gastric Secretions
•Intrinsic factor
Regulation of Gastric Secretion
• Cephalic
• Gastric
• Intestinal
• Stomach emptying
• 4 hours
• Liquids and carbs move out fast
• Proteins and fatty acids take longer
Small Intestine
• Functions
• Finishes digestion
• Absorbs nutrients
• Passes waste to large intestine
Small Intestine Secretions
• Neutral/alkaline fluid
• Mucus
• Peptidase
• Maltase, sucrase, lactase
• Lipase
• Secretin & cholecystokinin
Large Intestine
Large Intestine Functions
• Absorption of fluids and
• Waste elimination
• Produces and secretes bile
• Bile salts
• Many other non-digestive functions
including: plasma proteins, storing
glucose, detoxification of blood, and
biomolecule metabolism
• Stores and concentrates bile
• Endocrine function for glucose
• Digestive functions:
• Amylase
• Trypsinogen/trypsin
• Lipase
Chemical Digestion
• Breaks down complex molecules into
smaller ones that can be absorbed by
• Uses the process of hydrolysis
Carbohydrate Digestion
• Begins in the mouth
• Polysaccharides are broken down to
• In the small intestines, disaccharides
are broken down into
monosaccharides – glucose, fructose,
and galactose
Protein Digestion
• Begins in the stomach
• Breaks proteins into polypeptides
• In the small intestines, peptides are
reduced to amino acids (the building
blocks of proteins)
Lipid Digestion
• Only occurs in the small intestine
• Fats are emulsified by bile to decrease
attraction between the molecules
• Lipids are broken down to
monoglycerides and fatty acids (the
building blocks of lipids)
The Bottom Line
• We ingest approximately 10 liters of
materials a day.
• 9 liters or more are absorbed in the
small intestine.
• A meal takes approximately 24-72
hours to make a complete journey
through the digestive tract.