HUBS192 Overview

• Pre-lecture material for proper note-taking

• Not a substitute for live lectures

Course Structure

• Lectures 24-27:

  • Lecture 24: Introduction to gastrointestinal physiology, motility, and mechanical digestion

  • Lecture 25: Secretion in the gastrointestinal tract

  • Lecture 26: Chemical digestion in the gastrointestinal tract

  • Lecture 27: Absorption of nutrients, water, and sodium in the gastrointestinal tract

Key Learning Objectives

1. Regulation of the gastrointestinal tract:

   • Enteric nervous system

   • Parasympathetic and sympathetic nervous systems

   • Hormonal regulation

2. Long and short reflex pathways in gastrointestinal control.

3. Motility patterns for food processing:

   • Chewing, peristalsis, relaxation, contraction, segmentation, and MMC.

4. Functions of gastrointestinal motility:

   • Mechanical digestion, propulsion, mixing, storage, controlled movement, and exposure to absorptive surfaces.

5. Motility patterns of the mouth, oesophagus, stomach, and intestines.

Gastrointestinal Functions

• Motility: Movement of food/chyme through contraction and relaxation of muscles.

• Secretion: Release of fluids, enzymes, and components aiding digestion.

• Digestion: Breakdown of food into smaller components:

  • Mechanical and chemical digestion.

• Absorption: Movement of nutrients across intestinal lining into circulation.

Regulation of the GIT

• Nervous System Regulation:

  • Fast responses via ENS and muscle coordination.

  • Enteric Nervous System (ENS): Self-contained, operates independently.

  • Parasympathetic NS: Stimulates GIT activity (rest and digest).

  • Sympathetic NS: Inhibits GIT activity (fight or flight).

• Hormonal Regulation: Endocrine responses that last longer:

  • Important hormones: Gastrin, Secretin, CCK, GIP.

Motility Patterns in GIT

• Types of Contractions:

  • Tonic (sustained) and phasic (wave-like).

• Motility during Feeding:

  • Chewing, peristalsis, relaxation (storage), segmentation (mixing), and sphincter control.

• Fasting Motility:

  • Migrating Motor Complex (MMC): Housekeeping function post meal.

Specific Motility Patterns

• Mouth: Chewing (mastication).

• Oesophagus: Peristalsis (propelling food).

• Stomach: Retropulsion (mixing and mechanical digestion), relaxation to accommodate food.

• Small Intestine: Segmentation (mixing) and peristalsis (propulsion).

• Large Intestine: Storage and water absorption through segmentation and peristalsis.

Important Notes

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