GI tract disorders

• Essential organs in the gastrointestinal tract

  • Stomach
  • Small intestines
  • Colon
• Accessory organs/glands

  • Liver
  • Salivary glands
  • Pancreas
  • Gallbladder
• Layers of the stomach

  • Mucosa
  • Submucosa
  • Muscularis
  • Serosa
• What type of cells make up the mucosa

  Made of simple columnar epithelial cells
• What type of cells is the submucosa

  Made of areola connective tissue
• What is the Muscularis made up of

  3 layers of smooth muscle
• What is the Serosa made up of

  Squamous epithelial cells and areolar connective tissue
• Cells in the gastric pit

  • Surface mucous
  • Chief
  • Parietal
  • G-cells
• Surface mucus cells

  Secrete mucus
• Chief cells

  Produce pepsinogen and gastric lipase
• Parietal cells

  Produce intrinsic factor and Hydrochloric acid
• G-cells

  Stimulated by the vagus nerve to produce gastrin, which stimulates the production of gastric juices when food is present
• Vagus nerve

  Part of the parasympathetic nervous system and is involved in the rest-and-digest process
• Describe Hydrochloric acid production

  1. Water and carbon dioxide converted to carbonic acid using carbonic anhydrase

  2. Carbonic acid dissociates into protons and bicarbonate ions

  3. Proton pump uses ATP to pump protons into the chyme

  4. Chloride ions exchanged for bicarbonate ions in the bloodstream

  5. Chloride ions diffuse via ion channels into the chyme
• Parts of the small intestine

  • Duodenum
  • Jejunum
  • Ileum
• Role of the small intestine

  Absorption of nutrients
• Layers of the small intestine

  • Mucosa
  • Submucosa
  • Muscularis
  • Serosa
• Submucosa in the duodenum features

  
  

  Has duodenal glands that secrete alkaline mucus to neutralise chyme
• Duodenal digestion properties

  The duodenum receives chyme from the stomach, pancreatic enzymes and bile from the gallbladder
• Cells in the villi

  • Absorptive
  • Goblet
  • Enteroendocrine
  • Paneth
• Goblet cells

  Secrete mucus
• Enteroendocrine cells

  Secrete CCK and secretin
• Paneth cells

  Secrete lysozymes
• Absorptive cells

  Involved in nutrient absorption and are lined with microvilli
• Enzymes in the brush border

  • Lactases
  • Sucrases
  • Peptidases
  • Nucleases
  • Phosphatases
• Lactase

  Required to digest lactose
• Sucrases

  Used to digest sucrose
• Peptidases

  Used to break polypeptide chains
• Nucleases

  Used to break down DNA and RNA
• Phosphatases

  Used to break down phosphates
• Haematoxylin and Eosin (H&E) staining

  Used to view histological structures
• Haematoxylin

  Basic stain that stains acidic structures containing DNA blue
• Eosin

  Acidic stain that stains basic structures containing proteins red
• Helicobacter pylori

  Causes acute and chronic gastritis
• Gastritis

  Stomach inflammation
• Helicobacter pylori

  • Gram-negative bacteria which is extremely motile
• Main symptoms of Helicobacter pylori infection

  • Upper abdominal pain
  • Nausea
  • Vomiting
• How Helicobacter pylori causes ulcers

  1. Disrupts the mucus layer causing a break in the stomach lining

  2. Inflammation results in increased HCl and Pepsin secretion, causing tissue damage

  3. Ulcer formation
• How Helicobacter pylori survives in the stomach

  
  

  • Converts urea to ammonia and carbon dioxide using urease
  • NH3 and HCO3- neutralise HCl
• Treatment for gastric ulcers

  1. Antibiotics

  2. Proton-pump inhibitors to reduce HCl production