Gastrointestinal (Digestive) System
- Introduction
• The gastrointestinal (GI) system, also called the digestive system, is responsible for ingestion, digestion, absorption of nutrients, and elimination of waste.
• It includes a continuous muscular tube called the alimentary canal and several accessory organs.
• The main goal is to convert food into energy and building blocks for the body. - Components of the Gastrointestinal System
A. Alimentary Canal (GI Tract)
• Mouth – entry point for food; mechanical digestion by teeth and chemical digestion by saliva.
• Pharynx – passageway for food from mouth to esophagus.
• Esophagus – muscular tube that transports food to the stomach via peristalsis.
• Stomach – muscular sac that mixes food with gastric juices to continue digestion.
• Small Intestine – longest part; phases include duodenum, jejunum, ileum; main site for digestion and absorption.
• Large Intestine – absorbs water, salts, and forms feces; includes cecum, colon, rectum, and anus.
B. Accessory Organs
• Salivary glands – produce saliva that begins carbohydrate digestion and lubricates food.
• Liver – produces bile aiding fat digestion and detoxifies substances.
• Gallbladder – stores and concentrates bile, releasing it into the small intestine.
• Pancreas – produces digestive enzymes and bicarbonate to neutralize stomach acid. - Layers of the GI Tract Wall
- Mucosa – innermost layer that secretes mucus, digestive enzymes, and absorbs nutrients.
- Submucosa – connective tissue containing blood vessels, nerves, lymphatics.
- Muscularis externa – two muscle layers (circular and longitudinal) responsible for peristalsis and segmentation.
- Serosa (adventitia) – outer protective layer; serosa is a watery membrane for organs inside the peritoneal cavity.
- Functions of GI System Organs
Mouth
• Chewing mechanically breaks food.
• Saliva lubricates and starts starch digestion.
Esophagus
• Moves food to stomach by involuntary muscle contractions (peristalsis).
• Cardiac sphincter prevents acid reflux.
Stomach
• Stores food temporarily.
• Produces acid and enzymes for protein digestion.
• Mixes food into chyme.
Small Intestine
• Most digestion and nutrient absorption happen here.
• Digestive enzymes from pancreas and bile from liver assist.
• Rich blood supply absorbs nutrients into bloodstream.
Large Intestine
• Absorbs water and electrolytes.
• Converts waste into feces.
• Houses gut bacteria that aid digestion and produce vitamins.
Liver
• Produces bile, metabolizes nutrients, detoxifies harmful substances, stores vitamins.
Gallbladder
• Stores and releases bile into duodenum to emulsify fats.
Pancreas
• Produces digestive enzymes and bicarbonate for digestion. - Processes in the GI System
• Ingestion: Intake of food.
• Propulsion: Swallowing and peristalsis move food.
• Mechanical digestion: Chewing, churning, segmentation.
• Chemical digestion: Breakdown of macromolecules by enzymes.
• Absorption: Nutrients absorbed into blood or lymph.
• Defecation: Elimination of indigestible substances as feces. - Common Disorders of GI System
• Gastroesophageal reflux disease (GERD)
• Peptic ulcers
• Hepatitis
• Gallstones
• Inflammatory bowel disease (Crohn’s, ulcerative colitis)
• Constipation and diarrhea
• Colon cancer - Nursing Care and Considerations
• Monitor bowel habits, appetite, and digestive symptoms.
• Administer medications like antacids, laxatives, and enzyme supplements.
• Educate patients about nutrition, hydration, and lifestyle modifications.
• Assist with feeding tubes or parenteral nutrition if required.
• Prepare patients for diagnostic tests (endoscopy, colonoscopy).
• Support post-operative care for abdominal surgeries. - Summary for Quick Review
The gastrointestinal system includes the alimentary canal and accessory organs that work together to digest food, absorb nutrients, and eliminate waste. The mouth chews and moistens food, the esophagus transports it, the stomach mixes and digests proteins, and the small intestine absorbs nutrients. The large intestine absorbs water and forms feces. The liver, gallbladder, and pancreas contribute enzymes, bile, and fluids essential for digestion. Nursing care focuses on monitoring digestive health, managing disorders, and educating patients about nutrition.