Stomach and Abomasum - Pathology

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()Map ALIMENTARY SYSTEM (Map)



Introduction to the Stomach and Abomasum

  • In most animals, after swallowing, food leaves the oesophagus and enters the stomach. In ruminants, food enters the abomasum after fermentation in the forestomach.
  • The stomach acts as a reservoir in which a semi-solid mass (chyme) is formed from the ingested food before passing into the duodenum.
  • With the exception of water, little absorption occurs in the stomach.
  • Gastric juice is highly acidic, and contains:
    • HCl, produced by the parietal cells
      • Maintains gastric pH at 2, which denatures protein.
    • Pepsin, derived from pepsinogen, produced by zymogen cells
      • The action of HCl facilitates this.
  • Surface epithelial cells and mucous neck cells produce mucus which forms an alkaline sheet over the epithelial surface.
    • Provides protection from the gastric juice.
  • The cells of the mucosa are renewed at different rates. This is an important considerination in the pathogenesis of certain gastric diseases.
    • Surface epithelial cells and mucous neck cells are replaced about every 3 days.
    • Parietal cells and zymogen cells are produced at a slower rate; the parietal cells have a half-life of 23 days.

Defence Mechanisms

  1. Secretions :
    • Mucus (inhibits contact with mucosa, protects surface).
    • Acid (parietal cells)
    • Digestive enzymes (pepsin from gastric chief cells)
  2. Epithelium:
    • Provides a barrier
      • Stratified squamous epithelium; multilayered, high cell turnover
  3. Movement:
    • Continuous movement discourages persistence of insult at mucosa.

Inflammatory Conditions

Proliferative Pathology

Parasites

Physical Disruptions

Toxicology

Consequences of Gastric Disease