Chapter 3 Lecture (110) Blake 6e

Chapter Overview

  • Nutrition & You Sixth Edition (Chapter 3)

  • Focus on digestion processes essential for nutrient absorption and overall health.

Learning Outcomes for Chapter 3

  • Define Digestion: Multistep process for preparing food for nutrient absorption.

  • Digestive Organs: Identify organs involved and their primary functions, including GI tract anatomy.

  • Enzymes and Hormones: Explain the roles of enzymes, hormones, and bile in digestion.

  • Absorption: Describe absorption processes and nutrient transport via circulatory and lymphatic systems.

  • Regulatory Systems: Explore the roles of the nervous and endocrine systems in digestion.

  • Digestive Disorders: Discuss common digestive disorders, their symptoms, and causes.

What Is Digestion, and Why Is It Important?

Digestive Process

  • Definition: Breakdown of food into absorbable components via mechanical and chemical means in the gastrointestinal (GI) tract.

  • Length: GI tract measures approximately 30 feet.

  • Cell Renewal: Cells of the GI tract have a lifespan of 3-5 days before shedding into the intestinal lumen.

Components of the GI Tract

  • Anatomy:

    • Mouth: Entry point for ingestion.

    • Esophagus: Conveys food to the stomach.

    • Stomach: Mixes food with digestive juices.

    • Intestines: Includes both small and large intestines for digestion and absorption.

    • Accessory Organs: Such as pancreas, liver, and gallbladder that assist in digestion.

Digestion Is Mechanical and Chemical

Mechanical Digestion

  • Processes: Includes chewing, grinding, and the movement of food.

  • Peristalsis: Rhythmic muscle contractions move food through the esophagus and intestines.

Chemical Digestion

  • Digestive Juices: Enzymes and acids break down food into nutrients, facilitating absorption.

  • Segmentation: Mixing of chyme with digestive secretions enhances nutrient absorption time.

GI Tract Functions

Main Roles

  • Break down food into small components.

  • Absorb nutrients effectively.

  • Prevent harmful microorganisms from entering the body.

  • Maintain gut microbiome balance.

Organs of the GI Tract

Mouth

  • Ingestion and Mechanical Digestion: Chewing mixes food with saliva.

  • Chemical Digestion: Salivary amylase begins carbohydrate breakdown.

Esophagus

  • Propulsion: Swallowing and peristalsis move bolus to the stomach.

Stomach

  • Mechanical Digestion: Churning food.

  • Chemical Digestion: Enzymatic action begins protein digestion.

  • Absorption: Some fat-soluble substances absorbed.

Small Intestine

  • Primary Site of Digestion and Absorption: Enzymes from pancreas and bile from liver complete nutrient digestion.

Large Intestine

  • Absorbs Water and Nutrients: Compacts undigested food into feces.

Accessory Organs

  • Liver: Produces bile for fat digestion.

  • Pancreas: Secretes digestive enzymes and bicarbonate to neutralize gastric acid.

  • Gallbladder: Stores bile for fat emulsification.

Digestive Enzymes and Hormones

Hormonal Regulation

  • Gastrin, Secretin, Cholecystokinin: Hormones that help regulate digestion and enzyme activity.

Enzyme Functions

  • Amylase, Lipase, Proteases: Break down carbohydrates, fats, and proteins.

  • Bile: Essential for fat breakdown.

Nutrient Absorption

Mechanisms of Absorption

  • Passive Diffusion, Facilitated Diffusion, Active Transport: Describe how nutrients enter cells via intestinal walls.

  • Nutrient Distribution: Water-soluble nutrients enter circulatory system; fat-soluble nutrients enter lymphatic system.

Post-Absorption Nutrient Handling

  • Circulatory and lymphatic systems transport absorbed nutrients.

  • Excess nutrients can be stored in the body.

  • Excretory System: Elimination of waste.

Interaction with Other Body Systems

Nutritional Impact

  • Nervous System: Stimulates appetite via ghrelin hormone.

  • Endocrine System: Manages nutrient utilization through various hormones.

Nutritional Genomics

Study of Diet and Genes

  • Examines the relationship between food components and gene expression affecting health.

Common Digestive Disorders

Disorders by Section

  • Mouth/Throat: Gingivitis, dysphagia.

  • Esophagus: GERD, heartburn.

  • Stomach: Gastroenteritis, peptic ulcers.

  • Intestines: IBS, celiac disease, constipation.

Treatment Approaches

  • Lifestyle modifications, dietary adjustments, and medications according to the specific disorder.