The Digestive System

Functions Ingestion Mechanical digestion Chemical digestion Movements Absorption Elimination

Mouth

Teeth

Pharynx & Esophagus Both oropharynx and laryngopharynx Esophagus

Stomach

Gastric Secretions Mucus HCl Intrinsic factor Pepsinogen Gastrin

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 electrolytes Waste elimination

Liver Produces and secretes bile Bile salts Many other non-digestive functions including: plasma proteins, storing glucose, detoxification of blood, and biomolecule metabolism

Gallbladder Stores and concentrates bile

Pancreas Endocrine function for glucose homeostasis Digestive functions: Amylase Trypsinogen/trypsin Lipase

Chemical Digestion Breaks down complex molecules into smaller ones that can be absorbed by cells Uses the process of hydrolysis

Carbohydrate Digestion Begins in the mouth Polysaccharides are broken down to disaccharides 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.