The Gastrointestinal System

Introduction to the Gastrointestinal System

  • The gastrointestinal (GI) system processes nutrients and minerals needed for survival and disposes of waste.

  • Key topics include the anatomy, physiology, common diseases, and treatments of the GI system.

The Digestion Process

  • The GI system, also known as the digestive system, consists of:

    • GI Tract

      • A continuous tube from the mouth to the anus, including:

        • Mouth

        • Pharynx

        • Esophagus

        • Stomach

        • Small intestine

        • Large intestine

        • Rectum

    • Accessory Organs

      • Salivary glands

      • Liver

      • Pancreas

      • These organs aid mechanical and chemical digestion.

  • Four Major Functions of Digestion:

    • Ingestion: Entering food into the mouth, chewing, and swallowing.

    • Digestion: Physically and chemically breaking down food into smaller molecules.

      • Digestive Enzymes break down:

        • Proteins → Amino acids

        • Sugars → Simple sugars (e.g., Glucose)

        • Fats → Fatty acids and triglycerides

    • Absorption: Transferring digested food from the intestines into the bloodstream, mainly processed by the liver.

    • Elimination: Passing undigested food out of the body as stool.

Major Organs of the GI System

  • Mouth

    • Also called the oral/buccal cavity; functions to ingest and prepare food for digestion.

    • Teeth, tongue, and saliva assist in chewing and swallowing.

  • Pharynx

    • Common channel for air, food, and liquids; connects to the larynx, trachea, and esophagus.

  • Esophagus

    • A 10-12 inch long tube leading to the stomach.

    • Peristalsis: Muscle movements pushing food downward.

    • Lower Esophageal Sphincter prevents reflux into the esophagus.

  • Stomach

    • Has three parts:

      • Fundus: Broad portion near the esophagus.

      • Body: Central portion.

      • Pylorus: Narrow section leading to the small intestine.

    • Mucosa folds into rugae for expansion and contraction.

    • Secretes gastric juices (e.g., pepsin for protein digestion, hydrochloric acid for acidification and killing bacteria).

  • Small Intestine

    • About 20 feet long, divided into:

      • Duodenum: First 12 inches connecting to the stomach and receiving digestive juices.

      • Jejunum: The middle section (8 feet long) with villi for nutrient absorption.

      • Ileum: Last section (10-12 feet long) absorbs remaining nutrients.

  • Pancreas

    • Produces pancreatic juice with enzymes for digesting carbs, proteins, and fats:

      • Trypsin: Breaks down proteins.

      • Lipase: Breaks down fats.

      • Amylase: Breaks down carbohydrates.

    • Neutralizes gastric acid with sodium bicarbonate.

  • Liver

    • Largest gland; performs over 500 functions and produces 1,000+ enzymes.

    • Key jobs include:

      • Storing blood, filtering toxins.

      • Converting sugars to glycogen.

      • Maintaining blood sugar and sex hormone levels.

      • Producing blood-clotting proteins.

    • Can regenerate from only ¼ of its cells.

Large Intestine

  • About 5 feet long; functions to receive waste from small intestine, absorb water and sodium.

  • Divided into:

    • Cecum: Pouch joining small and large intestines.

    • Colon: Includes ascending, transverse, descending, and sigmoid segments.

    • Rectum: Terminal portion, regulated by anal sphincters for defecation.

GI Disorders

  • Gastrointestinal Inflammation: Can lead to irritation and ulcer formation.

    • Treatment targets offending agents; includes pain relievers, antibiotics.

  • Flatulence: Accumulated gas in GI tract.

    • Treated with simethicone.

  • Inflammatory Bowel Disease (IBD): Chronic inflammation, includes ulcerative colitis and Crohn’s disease; treated with specific medications (e.g., azulfidine).

  • Pancreatitis: Inflammation due to alcohol or gallstones, treated with IV fluids and pain management.

  • Cirrhosis: Liver deterioration; symptoms include abdominal pain, jaundice.

    • Treatment includes lifestyle changes and medications for viral infections.

  • Diarrhea: Watery stools, can be caused by infections or food toxins; treated with hydration.

  • Constipation: Difficult stool passage; prevented with fiber, hydration, and exercise.

  • Nausea and Vomiting: Caused by various factors, treat with anti-nausea meds.

  • Gastro-Esophageal Reflux Disease (GERD): Caused by acid backing up into the esophagus; lifestyle modifications can alleviate.

  • Peptic Ulcers: Wounds in the GI mucosa caused by toxins or infections; treated by avoiding irritants.

Key Points

  • IBD includes ulcerative colitis and Crohn’s disease.

  • Nausea can stem from various conditions; often anti-nausea medications are used in treatment.

  • The pancreas secretes enzymes crucial for digesting carbs, proteins, and fats.

  • Small intestine consists of the duodenum, jejunum, and ileum.

  • The large intestine is segmented into various colon portions named for their shape.

  • The liver is unique in its regenerative capabilities.

GI Disorders and Associated Medications

  • Gastrointestinal Inflammation: Treatment targets offending agents; includes pain relievers and antibiotics.

  • Flatulence: Treated with simethicone.

  • Inflammatory Bowel Disease (IBD): Specific medications include azulfidine (sulfasalazine) for treatment.

  • Pancreatitis: Treated with IV fluids and pain management.

  • Cirrhosis: Treatment includes lifestyle changes and medications for viral infections.

  • Diarrhea: Treated with hydration and sometimes medications like loperamide.

  • Constipation: Prevented with fiber, hydration, and exercise; laxatives may also be used.

  • Nausea and Vomiting: Treated with anti-nausea medications like ondansetron or metoclopramide.

  • Gastro-Esophageal Reflux Disease (GERD): Lifestyle modifications; medications include proton pump inhibitors (e.g., omeprazole).

  • Peptic Ulcers: Treated by avoiding irritants and medications such as proton pump inhibitors or H2-receptor antagonists.