Gastrointestinal System - AIT's Version 7 Exam Focus

Overview

• Understanding the journey of food and water in the human body
• Focus on the digestive system's four essential functions:
  • Ingestion
  • Digestion
  • Absorption
  • Elimination

Ingestion

• Intake of food
• Initiates with food entry into the mouth
• Saliva released at the thought of food
• Saliva contains enzymes for chemical digestion (e.g., salivary amylase for carbohydrates)
• Mechanical digestion via teeth grinding
• Saliva's role:
  • Contains digestive enzymes
  • Buffers to neutralize mouth acidity
  • Lubricates food for easier swallowing

Digestion

• Mechanical: Physical breakdown in the mouth
• Chemical: Enzymatic breakdown begins in the mouth
• Epiglottis covers windpipe during swallowing
• Peristalsis: Wave-like muscle contractions move food down the esophagus
• Stomach:
  • Capacity: ~2 liters
  • Acidic environment aids chemical digestion
  • Gastric juices: Hydrochloric acid, pepsin
  • Mechanical digestion: Churning of stomach contents creating a semi-liquid mixture called chyme
  • Important sphincters:
    • Lower esophageal sphincter: Prevents acid reflux from stomach
    • Pyloric sphincter: Controls passage of chyme into the small intestine

Absorption

• Small Intestine: Digestion ends, absorption begins
  • Sections: Duodenum, Jejunum, Ileum
  • Duodenum: Shortest, follows stomach, key for chemical digestion
    • Enzymes from pancreas, bile from liver
    • Absorbs iron and minerals
  • Jejunum: Middle section, nutrient absorption
    • Villi increase surface area
    • Absorbs carbohydrates and proteins
  • Ileum: Final section
    • Absorbs vitamin B12, bile salts, fat-soluble vitamins (A, D, E, K)
• Large Intestine: Water absorption, feces formation
  • Sections: Ascending colon, Transverse colon, Descending colon
  • Ascending colon: Absorbs water/salt, solidifies waste
  • Transverse colon: Stores waste, continues absorption
  • Descending colon: Prepares waste for elimination

Elimination

• Rectum: Final stage of digestive system
• Stores feces for expulsion

Accessory Organs

• Liver: Largest internal organ, metabolism of carbohydrates/proteins, produces bile
• Gallbladder: Stores bile
• Pancreas: Produces digestive enzymes, neutralizes acidic chyme

Hormones and Enzymes

• Gastrin: Stimulates gastric gland secretions
• Cholecystokinin (CCK): Digest fats/proteins, stimulates bile release
• Secretin: Regulates pH in duodenum, inhibits gastric acid, stimulates bicarbonate
• Insulin: Glucose metabolism, lowers blood sugar
• Glucagon: Raises blood glucose levels
• Bile: Emulsifies fats, aids lipid digestion

Tips for Remembering

• Small Intestine: Duodenum (Digestive), Jejunum (Juices - Absorption), Ileum (Intake - Complete absorption)
• Large Intestine: Ascending (Absorbs), Transverse (Transports), Descending (Drives down)

Resources

• Visit Nurse Chun's Store for additional AIT's exam resources.

This guide should serve as a comprehensive review of the human digestive system focusing on the AIT's Version 7 exam content.