Digestive

• General Structure


  • Hollow tube with lumen made up of 4 Main Layers: Mucosa, Submucosa, Muscularis, Serosa
• Mucosa


  • Epithelial lining
• Submucosa


  • Dense Connective Tissue
• Muscularis


  • Smooth Muscle Cells
• Serosa


  • Loose Connective Tissue
• Serosa


  • Small and Large Intestines continuous with portions of the Mesentery
• Oral Cavity


  • Stratified Squamous Epithelium (Keratinized, Partially Keratinized, or Nonkeratinized)
• Tongue


  • Mass of Striated Muscle covered by mucosa
• Filiform Papillae


  • Numerous, Elongated Conical Shape
• Fungiform Papillae


  • Less Numerous, Lightly Keratinized
• Foliate Papillae


  • Parallel Ridges on sides of tongue
• Vallate (Circumvallate) Papillae


  • Largest Papillae
• Teeth


  • Adult: 32 permanent teeth
• Parts of a Tooth

  • Crown – exposed portion
• Structure of Tooth


  • Enamel – hardest structure of the body, secreted by Ameloblasts
• Esophagus


  • Mucosa thrown into longitudinal folds giving the lumen an irregular or stellate shape
• Esophagus: Submucosa


  • Dense collagenous tissue
• Esophageal Glands


  • Both the Superficial and Deep esophageal glands secrete mucus to lubricate mucosal surface to facilitate passage of food
• Esophagus: Muscularis Externa


  • Arranged in layers - Inner circular and Outer longitudinal
• Esophagus: Tunica Serosa


  • Loose connective tissue
• Stomach


  • Most expanded portion of the GI tract
• Stomach: Mucosa


  • Simple Columnar Epithelium without Goblet Cells
• Stomach: Muscularis Mucosa


  • Formed of 2 layers of smooth muscle: Inner circular and Outer longitudinal
• Stomach: Submucosa


  • Loose connective tissue
• Stomach: Muscular Externa


  • Consists of 3 layers of smooth muscles: Inner oblique, Middle circular, Outer longitudinal
• Stomach: Tunica Serosa


  • Visceral peritoneal layer made of loose connective tissue
• Cells Found in Gastric Glands

  • Mucous neck cells - Pale staining, mucous secreting columnar cells
• 3 Types of Gastric Glands

  • Fundic Glands - Most numerous type, simple branched tubular glands, slightly coiled, all types of cells are present, gastric pits are occupying 1/4 thickness of mucosa, lumen is narrow
• Small Intestine


  • Portion between the stomach and large intestine
• Idal cells


  Acidophilic cytoplasm<|>Found between the chief cells and basement membrane<|>Secrete HCl and Intrinsic Factor
• Argentaffin cells or Entero-chromaffin cells


  Pyramidal or flattened cells<|>Secrete Serotonin and Histamine<|>Found in the walls of: Stomach, Small and large intestines
• Types of gastric glands

  • Fundic glands
  • Pyloric glands
  • Cardial glands
• Fundic glands


  • Most numerous type
  • Simple branched tubular glands, slightly coiled
  • All types of cells are present
  • Gastric pits are occupying ¼ thickness of mucosa
  • Lumen is narrow
• Pyloric glands


  • Coiled tubular glands
  • Gastric pits are long and deep extending to about ½ the thickness of mucosa
  • Lumen is wider
  • No parietal cells except in pyloric sphincter
• Cardial glands


  • Simple tubular glands (some compound tubular)
  • Terminal end is long coiled
  • Gastric pits are short and shallow
  • The glandular cells are mostly mucous secreting
• The small intestine is the portion between the stomach and the large intestine
• Small intestine


  • Anchored to the posterior body wall by means of the Mesentery
  • Digestion is completed in this part
  • Mainly responsible for absorption of nutrients
  • Average length: app 5 meters
  • 3 segments: Duodenum, Jejunum, Ileum
• Modifications in the Mucosa and Submucosa of the Small Intestine

  • Horizontal mucosal folds
  • Intestinal villi
  • Microvilli
• Horizontal mucosal folds


  Plicae Circulares or Valves of Kerckring<|>The luminal surface of the SI is wrinkled when examined with the naked eye<|>Consist of mucosa and submucosa
• Horizontal mucosal folds


  • Most developed in the jejunum
  • Absent in the first part of the duodenum and distal half of the ileum