Intro to GI, Assessment, & Dx Tests Lecture 6 WK 4

Introduction to the Gastrointestinal System

  • The gastrointestinal (GI) system is also called the digestive tract or alimentary canal.

  • It is a muscular tube, lined with a mucous membrane, approximately 30 feet long, extending from the mouth to the anus.

  • Components: mouth, pharynx, esophagus, stomach, small intestine, large intestine and anus.

Anatomy and Physiology Overview

  • Peristalsis:

    • Definition: Coordinated rhythmic contractions of smooth muscle that push food through the digestive tract.

  • Accessory organs:

    • Not part of the digestive tract but aid in digestion (teeth, tongue, salivary glands, liver, gallbladder, pancreas, appendix).

    • Release digestive chemicals into the system through ducts.

The Mouth and Its Functions

  • The mouth as the entry point of the digestive system.

  • Tongue functions: Chewing, swallowing, and talking.

  • Papillae: Tiny elevations on the tongue containing taste buds.

  • Digestion begins in the mouth: teeth shred and grind food; enzymes begin chemical breakdown of carbohydrates.

Teeth

  • Types of teeth:

    • Incisors: Biting and cutting (front teeth).

    • Canines: Tearing and shredding food.

    • Molars: Used for mastication (crushing and grinding).

Salivary Glands

  • Types: Parotid, submandibular, sublingual.

  • Saliva Composition: 99% water, enzymes, mucus.

  • Role: Increases when food is present to lubricate and dissolve food for digestion.

  • Daily secretion: About 1,000 to 1,500 mL of saliva.

The Esophagus

  • Muscular, collapsible tube extending from mouth to stomach.

  • Peristalsis moves a bolus of food through the pharynx to the esophagus, and then to the stomach within 5 to 6 seconds.

The Stomach

  • Location: Left upper quadrant of the abdomen.

  • Capacity: Holds 1 to 1.5 liters, approximately the size of a football.

  • Sphincters:

    • Cardiac sphincter: Entrance to the stomach.

    • Pyloric sphincter: Exit from the stomach.

  • Functions: Mix food with gastric juices, transforming it into chyme, which passes through the pyloric sphincter into the duodenum.

The Small Intestine

  • Length: Approximately 20 feet long, 1 inch in diameter.

  • Starts at pyloric sphincter, ends at ileocecal valve.

  • Sections:

    • Duodenum

    • Jejunum

    • Ileum

  • Main functions: 90% of digestion and metabolism of carbohydrates and proteins occur here.

  • Villi: Inner surface contains finger-like projections to aid digestion and absorption.

The Large Intestine

  • Length: About 5 to 6 feet, 2 inches in diameter.

  • Components: Cecum, appendix, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, rectum, anus.

  • Major functions:

    • Absorption of water.

    • Manufacturing of certain vitamins.

    • Formation and expulsion of feces.

  • Bacteria in the large intestine convert waste to fecal material.

The Liver

  • Location: Inferior to the diaphragm, in the upper right quadrant.

  • Structure: Divided into two lobes.

  • Blood supply: Approximately 1,500 mL of blood delivered every minute.

  • Functions: Produces bile (aids in fat digestion), bile travels to the gallbladder for storage.

The Gallbladder

  • Function: Stores and ejects bile into the duodenum for fat digestion.

  • Location: Pear-shaped organ connected to the underside of the liver.

The Pancreas

  • Location: Posterior to the stomach.

  • Function: Produces pancreatic juice containing enzymes (protease, amylase, lipase) for digestion.

  • Secretes sodium bicarbonate for neutralizing stomach acid and aids in glucose regulation.

Assessment of the GI System

  • Health History:

    • Ask about:

      • Abdominal pain, bowel patterns (changes), unexplained weight changes, previous GI disorders, and surgeries.

      • Medications: prescription drugs (e.g., aspirin, NSAIDs), vitamins, antacids, laxatives, herbal supplements.

    • Nutritional Assessment:

      • Normal food/fluid intake, meal frequency, allergies, appetite patterns, nutritional supplements.

      • Age-related energy requirements – increased caloric need during growth phases (infancy, adolescence, pregnancy).

      • Consider cultural influences on diet (e.g., rice consumption in Asian cultures).

      • Other factors: Who cooks, meal timing, food preferences, swallowing difficulties, activity levels, alcohol use, diets (medical or self-imposed).