29.1 Introduction to the Gastrointestinal System and Oral Cavity

The gastrointestinal system is a complex network of organs working together to break down food and absorb nutrients. From the mouth to the anus, each part plays a crucial role in digestion, with accessory organs like the liver and pancreas lending a helping hand.

Understanding how this system works is key for nurses. We'll look at common oral cavity issues that can mess with digestion, and explore how the liver, pancreas, and gallbladder pitch in to keep things running smoothly. It's all about teamwork in your gut!

Gastrointestinal System Overview

Structure and function of the gastrointestinal system from ingestion to elimination

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• Oral cavity
  • Mechanical digestion begins with chewing (mastication) breaks food into smaller pieces increasing surface area for enzymes to act upon
  • Chemical digestion initiated by salivary amylase begins breaking down complex carbohydrates (starch) into simpler sugars (maltose)
• Pharynx and esophagus
  • Food is swallowed and propelled by peristalsis rhythmic muscular contractions that push food through the digestive tract
• Stomach
  • Mechanical digestion through muscular contractions churns and mixes food with gastric secretions
  • Chemical digestion by gastric acid (HCl) and pepsin (protein-digesting enzyme) breaks down proteins into smaller peptides
  • Chyme is produced a semi-liquid mixture of partially digested food and digestive secretions
• Small intestine
  • Duodenum, jejunum, and ileum three segments of the small intestine
  • Majority of chemical digestion and nutrient absorption occurs here with the help of intestinal enzymes, bile, and pancreatic secretions
  • Bile from liver and digestive enzymes from pancreas aid digestion by emulsifying fats and breaking down macronutrients
• Large intestine
  • Absorption of water and electrolytes (sodium, potassium, chloride) to form solid waste
  • Formation of feces through the action of gut bacteria and removal of remaining water
• Rectum and anus
  • Storage and elimination of feces through the process of defecation

Oral Cavity and Accessory Organs

Common disorders affecting the oral cavity and their impact on digestion

• Dental caries (cavities)
  • Bacterial decay of teeth caused by acid production from oral bacteria metabolizing sugars
  • Can lead to difficulty chewing and improper mechanical digestion resulting in larger food particles entering the digestive tract
• Gingivitis and periodontitis
  • Inflammation and infection of gums and supporting structures caused by bacterial buildup (plaque)
  • May cause pain and difficulty eating leading to reduced food intake and potential nutrient deficiencies
• Oral thrush
  • Fungal infection (Candida albicans) often seen in immunocompromised individuals or those using inhaled corticosteroids
  • Can cause painful lesions and interfere with food intake leading to reduced nutrient absorption
• Xerostomia (dry mouth)
  • Reduced saliva production often caused by medications, dehydration, or certain medical conditions (Sjögren's syndrome)
  • Impairs chemical digestion and increases risk of dental caries due to lack of salivary enzymes and buffering capacity

Roles of accessory organs like the liver, pancreas, and gallbladder in the digestive process

• Liver
  • Produces bile, which emulsifies fats breaking them into smaller droplets for easier digestion by pancreatic lipase
  • Metabolizes nutrients (carbohydrates, proteins, fats) and detoxifies harmful substances (alcohol, drugs) to maintain homeostasis
• Gallbladder
  • Stores and concentrates bile produced by the liver
  • Releases bile into the duodenum when stimulated by cholecystokinin a hormone released in response to fat and protein in the small intestine
• Pancreas
  • Exocrine function: secretes digestive enzymes into the duodenum through the pancreatic duct
    • Pancreatic amylase: digests carbohydrates breaking down starches and complex sugars into simpler sugars (glucose)
    • Trypsin and chymotrypsin: digest proteins breaking them down into smaller peptides and amino acids
    • Pancreatic lipase: digests fats breaking down triglycerides into fatty acids and monoglycerides
  • Endocrine function: secretes insulin and glucagon to regulate blood glucose levels maintaining glucose homeostasis