HE330 - Lecture3 - Students

Lecture Overview

Instructor: Christine M. Mills, RD, MPH, PhD Course: HE330 Human Nutrition & Health

Digestion, Absorption, and Metabolism

Gastrointestinal Tract

• Structure of the Gastrointestinal Tract and Gut Wall: Consists of mouth, pharynx, esophagus, stomach, intestines, anus.

• Components of Digestive Secretions: Includes saliva, gastric juices (HCl, pepsinogen, intrinsic factor), bile, and pancreatic juices.

• Regulation of Gastrointestinal Function: Governed by hormonal signals (e.g., gastrin, secretin) and neural regulation.

• Barrier Function: Protects against pathogens and toxins through mucosal immunity.

Role of Digestive Organs

• Mouth: Initiates mechanical digestion; saliva moistens food and contains enzymes like salivary amylase for carbohydrate digestion.

• Epiglottis: Prevents aspiration during swallowing, directing food towards the esophagus.

• Esophagus: Transports food to the stomach via peristalsis, rhythmic muscle contractions.

• Stomach: Produces chyme, mixes and stores food; gastric juices digest proteins.

• Small Intestine: Primary site for digestion and absorption; divided into duodenum, jejunum, ileum; lined with villi and microvilli to increase surface area. Receives bile from the liver and pancreatic juices for fat digestion.

• Large Intestine: Absorbs water and vitamins, prepares waste for excretion; houses beneficial intestinal bacteria.

Impact of Microbiota and Health

• Microbiota's Impact: Influences digestion, immune function, and may contribute to metabolic health.

• Common Digestive Problems: Heartburn/GERD (acid reflux discomfort), ulcers (erosion of the GI lining), diarrhea (loose stools due to infections), and constipation (related to fiber/water intake).

• Nutritional Implications: Understanding digestive processes is crucial for ensuring proper nutrient absorption and managing health outcomes.

Importance of the Cardiovascular System

• Significance in Nutrition: Essential for transporting absorbed nutrients to cells throughout the body.

• Amino Acid and Fatty Acid Transport: Different pathways for amino acids and long-chain fatty acids from absorption in the intestines to delivery at the cellular level.

Metabolic Processes

• Catabolic vs. Anabolic Pathways: Catabolism breaks down molecules for energy; anabolism builds complex molecules from simpler ones, including processes of cellular respiration.

• Anabolic Metabolism Products: Key building blocks for energy storage and structural components of cells.

• Routes for Waste Elimination: Including feces, urine, and through breath.

Food and Biological Structure

• Levels of Organization:

  • Atoms: Basic building blocks (C, H)

  • Molecules: Combinations of atoms

  • Cells: Basic units of life

  • Tissues: Groups of similar cells

  • Organs: Structures made of different tissues

  • Organ Systems: Groups of organs functioning together