Digestive System Overview

Key Functions

• Ingestion: Intake of food.
• Digestion: Mechanical and chemical breakdown of food.
• Absorption: Uptake of nutrients into the bloodstream.
• Elimination: Removal of waste products.

Organs Involved

• Mouth: Mechanical digestion (chewing) and chemical digestion (saliva).
• Pharynx: Passageway for food and air.
• Esophagus: Tube that carries food from the pharynx to the stomach.
• Stomach: Stores food, mixes it with gastric juices, and initiates protein digestion.
• Small Intestine: Major site of nutrient absorption, consisting of duodenum, jejunum, and ileum.
• Large Intestine: Absorbs water and electrolytes; forms and stores feces, consisting of cecum, colon, and rectum.
• Liver: Produces bile, crucial for fat digestion and absorption.
• Gallbladder: Stores and concentrates bile.
• Pancreas: Produces enzymes for digestion of carbohydrates, proteins, and fats.

Digestive Processes in Detail

• Mechanical Digestion: Physical breakdown of food, e.g., chewing, stomach churning, small intestine segmentation.
• Chemical Digestion: Breakdown of food into smaller molecules using enzymes. Enzymes are specific for nutrients, breaking down starch, proteins, and fats into absorbable monosaccharides, amino acids, and fatty acids.
• Absorption: Nutrients absorbed through the walls of the small intestine into the bloodstream. Villi and microvilli increase the surface area for absorption.

Types of Nutrients and their Digestion

• Carbohydrates: Broken down into monosaccharides (primarily glucose) through enzyme action.
• Proteins: Broken down into amino acids in the stomach and small intestine via enzyme action.
• Lipids/Fats: Broken down into fatty acids and glycerol. Bile salts from the liver emulsify fats for easier digestion.

Regulatory Mechanisms

• Nervous system and hormones (e.g., gastrin, secretin, cholecystokinin) regulate digestion, stimulating or inhibiting secretions and motility.

Digestive System Disorders

• Gastroesophageal reflux disease (GERD): Acid reflux into the esophagus.
• Peptic ulcers: Sores in the stomach or duodenum lining.
• Irritable bowel syndrome (IBS): Functional large intestine disorder.
• Inflammatory bowel disease (IBD): Chronic inflammation of the digestive tract.
• Diverticulosis: Formation of pouches in the colon.
• Diverticulitis: Infected pouches in the colon.

Importance of a Healthy Digestive System

• Proper nutrient absorption maintains well-being.
• Digestive issues can lead to malnutrition, vitamin deficiencies, and chronic conditions.
• A healthy diet, hydration, and lifestyle choices support the digestive system.

Accessory Organs

• Liver, gallbladder, and pancreas (accessory organs, not part of the alimentary canal) are vital. They produce and secrete fluids (bile and pancreatic juice), essential for breakdown and absorption.