Human Physiology

9.

The Digestive System

9.1.

Overview of Digestive Functions

9.1.1.

Mechanical Digestion

9.1.1.1.

9.1.1.2.

Gastric Churning

9.1.1.3.

9.1.1.4.

9.1.2.

Chemical Digestion

9.1.2.1.

Enzymatic Breakdown

9.1.2.2.

Acid Hydrolysis

9.1.2.3.

Bile Emulsification

9.1.3.

Absorption Processes

9.1.3.1.

Nutrient Uptake

9.1.3.2.

Water Absorption

9.1.3.3.

Electrolyte Absorption

9.1.4.

Motility Patterns

9.1.4.1.

Propulsive Movements

9.1.4.2.

Mixing Movements

9.1.4.3.

Sphincter Control

9.2.

Gastrointestinal Tract Structure

9.2.1.

9.2.1.1.

9.2.1.1.1.

9.2.1.1.2.

9.2.1.1.3.

Muscularis Mucosae

9.2.1.2.

9.2.1.2.1.

Connective Tissue

9.2.1.2.2.

9.2.1.2.3.

Submucosal Plexus

9.2.1.3.

Muscularis Externa

9.2.1.3.1.

Circular Muscle

9.2.1.3.2.

Longitudinal Muscle

9.2.1.3.3.

Myenteric Plexus

9.2.1.4.

9.2.1.4.1.

Visceral Peritoneum

9.2.2.

Regional Specializations

9.2.2.1.

Structural Adaptations

9.2.2.2.

Functional Modifications

9.3.

Neural and Hormonal Control

9.3.1.

Enteric Nervous System

9.3.1.1.

Myenteric Plexus

9.3.1.1.1.

9.3.1.1.2.

Peristalsis Coordination

9.3.1.2.

Submucosal Plexus

9.3.1.2.1.

Secretory Control

9.3.1.2.2.

9.3.2.

Autonomic Control

9.3.2.1.

Sympathetic Effects

9.3.2.1.1.

Inhibitory Actions

9.3.2.1.2.

Vasoconstriction

9.3.2.2.

Parasympathetic Effects

9.3.2.2.1.

Stimulatory Actions

9.3.2.2.2.

Secretion Enhancement

9.3.3.

Gastrointestinal Hormones

9.3.3.1.

9.3.3.1.1.

Gastric Acid Stimulation

9.3.3.1.2.

Gastric Motility

9.3.3.2.

Cholecystokinin

9.3.3.2.1.

Pancreatic Enzyme Release

9.3.3.2.2.

Gallbladder Contraction

9.3.3.3.

9.3.3.3.1.

Pancreatic Bicarbonate

9.3.3.3.2.

Gastric Acid Inhibition

9.3.3.4.

Glucose-Dependent Insulinotropic Peptide

9.3.3.4.1.

Insulin Release

9.3.3.4.2.

Gastric Inhibition

9.4.

Regional Digestive Physiology

9.4.1.

Oral Cavity and Pharynx

9.4.1.1.

Salivary Secretion

9.4.1.1.1.

Salivary Glands

9.4.1.1.1.1.

9.4.1.1.1.2.

Submandibular Glands

9.4.1.1.1.3.

Sublingual Glands

9.4.1.1.2.

Saliva Composition

9.4.1.1.2.1.

Water and Electrolytes

9.4.1.1.2.2.

9.4.1.1.2.3.

Antimicrobial Factors

9.4.1.1.3.

Salivary Control

9.4.1.1.3.1.

Neural Regulation

9.4.1.1.3.2.

Reflex Mechanisms

9.4.1.2.

9.4.1.2.1.

Mechanical Breakdown

9.4.1.2.2.

Bolus Formation

9.4.1.3.

9.4.1.3.1.

9.4.1.3.2.

Pharyngeal Phase

9.4.1.3.3.

Esophageal Phase

9.4.2.

9.4.2.1.

Esophageal Motility

9.4.2.1.1.

Primary Peristalsis

9.4.2.1.2.

Secondary Peristalsis

9.4.2.2.

Sphincter Function

9.4.2.2.1.

Upper Esophageal Sphincter

9.4.2.2.2.

Lower Esophageal Sphincter

9.4.2.3.

Protective Mechanisms

9.4.2.3.1.

Mucus Secretion

9.4.2.3.2.

Bicarbonate Production

9.4.3.

9.4.3.1.

Gastric Secretion

9.4.3.1.1.

Gastric Juice Composition

9.4.3.1.1.1.

Hydrochloric Acid

9.4.3.1.1.2.

9.4.3.1.1.3.

Intrinsic Factor

9.4.3.1.1.4.

9.4.3.1.2.

Secretory Cells

9.4.3.1.2.1.

9.4.3.1.2.2.

9.4.3.1.2.3.

9.4.3.1.2.4.

9.4.3.1.3.

Phases of Secretion

9.4.3.1.3.1.

9.4.3.1.3.2.

9.4.3.1.3.3.

Intestinal Phase

9.4.3.2.

Gastric Motility

9.4.3.2.1.

Receptive Relaxation

9.4.3.2.2.

9.4.3.2.3.

Gastric Emptying

9.4.3.2.4.

Migrating Motor Complex

9.4.3.3.

Gastric Protection

9.4.3.3.1.

Mucus-Bicarbonate Barrier

9.4.3.3.2.

Prostaglandin Effects

9.4.3.3.3.

Epithelial Renewal

9.4.4.

Small Intestine

9.4.4.1.

Intestinal Secretions

9.4.4.1.1.

Intestinal Juice

9.4.4.1.2.

Brush Border Enzymes

9.4.4.1.3.

Mucus Production

9.4.4.2.

Intestinal Motility

9.4.4.2.1.

9.4.4.2.2.

9.4.4.2.3.

Migrating Motor Complex

9.4.4.3.

Absorption Mechanisms

9.4.4.3.1.

Villus Structure

9.4.4.3.2.

9.4.4.3.3.

Transport Systems

9.4.4.3.3.1.

Active Transport

9.4.4.3.3.2.

Facilitated Diffusion

9.4.4.3.3.3.

Simple Diffusion

9.4.5.

Large Intestine

9.4.5.1.

Colonic Functions

9.4.5.1.1.

Water Absorption

9.4.5.1.2.

Electrolyte Absorption

9.4.5.1.3.

Bacterial Fermentation

9.4.5.2.

Colonic Motility

9.4.5.2.1.

Haustral Contractions

9.4.5.2.2.

9.4.5.2.3.

Defecation Reflex

9.4.5.3.

Microbiome Functions

9.4.5.3.1.

Vitamin Synthesis

9.4.5.3.2.

Short-Chain Fatty Acids

9.4.5.3.3.

Immune Interactions

9.5.

Accessory Organ Functions

9.5.1.

9.5.1.1.

Bile Production

9.5.1.1.1.

Bile Acid Synthesis

9.5.1.1.2.

Bile Composition

9.5.1.1.3.

Enterohepatic Circulation

9.5.1.2.

Metabolic Functions

9.5.1.2.1.

Carbohydrate Metabolism

9.5.1.2.2.

Lipid Metabolism

9.5.1.2.3.

Protein Metabolism

9.5.1.2.4.

Drug Metabolism

9.5.1.3.

Storage Functions

9.5.1.3.1.

Glycogen Storage

9.5.1.3.2.

Vitamin Storage

9.5.1.3.3.

Mineral Storage

9.5.1.4.

Synthetic Functions

9.5.1.4.1.

Plasma Protein Synthesis

9.5.1.4.2.

Clotting Factor Production

9.5.2.

9.5.2.1.

9.5.2.1.1.

Concentration Mechanisms

9.5.2.1.2.

Storage Capacity

9.5.2.2.

9.5.2.2.1.

CCK Stimulation

9.5.2.2.2.

Gallbladder Contraction

9.5.2.2.3.

Sphincter of Oddi

9.5.3.

9.5.3.1.

Exocrine Functions

9.5.3.1.1.

Pancreatic Juice Secretion

9.5.3.1.2.

Digestive Enzymes

9.5.3.1.2.1.

9.5.3.1.2.2.

9.5.3.1.2.3.

9.5.3.1.2.4.

9.5.3.1.3.

Bicarbonate Secretion

9.5.3.2.

Endocrine Functions

9.5.3.2.1.

Insulin Secretion

9.5.3.2.2.

Glucagon Secretion

9.5.3.2.3.

Somatostatin Secretion

9.6.

Nutrient Digestion and Absorption

9.6.1.

Carbohydrate Processing

9.6.1.1.

Starch Digestion

9.6.1.1.1.

Salivary Amylase

9.6.1.1.2.

Pancreatic Amylase

9.6.1.2.

Disaccharide Hydrolysis

9.6.1.2.1.

Brush Border Enzymes

9.6.1.2.2.

9.6.1.2.3.

9.6.1.2.4.

9.6.1.3.

Monosaccharide Absorption

9.6.1.3.1.

Glucose Transport

9.6.1.3.2.

Fructose Transport

9.6.1.3.3.

Galactose Transport

9.6.2.

Protein Processing

9.6.2.1.

Protein Denaturation

9.6.2.1.1.

Gastric Acid Effects

9.6.2.2.

Proteolytic Digestion

9.6.2.2.1.

9.6.2.2.2.

Pancreatic Proteases

9.6.2.2.3.

Brush Border Peptidases

9.6.2.3.

Amino Acid Absorption

9.6.2.3.1.

Transport Systems

9.6.2.3.2.

Peptide Transport

9.6.3.

Lipid Processing

9.6.3.1.

Fat Emulsification

9.6.3.1.1.

Bile Acid Functions

9.6.3.1.2.

Micelle Formation

9.6.3.2.

9.6.3.2.1.

Pancreatic Lipase

9.6.3.2.2.

9.6.3.3.

9.6.3.3.1.

Fatty Acid Uptake

9.6.3.3.2.

Chylomicron Formation

9.6.3.3.3.

Lymphatic Transport

9.6.4.

Vitamin and Mineral Absorption

9.6.4.1.

Fat-Soluble Vitamins

9.6.4.1.1.

Micelle-Dependent Absorption

9.6.4.2.

Water-Soluble Vitamins

9.6.4.2.1.

Specific Transporters

9.6.4.2.2.

B12-Intrinsic Factor

9.6.4.3.

Mineral Absorption

9.6.4.3.1.

Iron Absorption

9.6.4.3.2.

Calcium Absorption

9.6.4.3.3.

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