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| − | ==Introduction to the Stomach and Abomasum==
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| − | * In most animals, after swallowing, food leaves the [[Oesophagus - Anatomy & Physiology|oesophagus]] and enters the [[Forestomach - Anatomy & Physiology|stomach]]. In ruminants, food enters the [[The Abomasum - Anatomy & Physiology|abomasum]] after fermentation in the forestomach.
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| − | * The [[Forestomach - Anatomy & Physiology|stomach]] acts as a reservoir in which a semi-solid mass (chyme) is formed from the ingested food before passing into the [[Duodenum - Anatomy & Physiology|duodenum]].
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| − | * With the exception of water, little absorption occurs in the [[Forestomach - Anatomy & Physiology|stomach]].
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| − | * Gastric juice is highly acidic, and contains:
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| − | ** HCl, produced by the parietal cells
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| − | *** Maintains gastric pH at 2, which denatures protein.
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| − | ** Pepsin, derived from pepsinogen, produced by zymogen cells
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| − | *** The action of HCl facilitates this.
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| − | * Surface epithelial cells and mucous neck cells produce mucus which forms an alkaline sheet over the epithelial surface.
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| − | ** Provides protection from the gastric juice.
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| − | * The cells of the mucosa are renewed at different rates. This is an important considerination in the pathogenesis of certain gastric diseases.
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| − | ** Surface epithelial cells and mucous neck cells are replaced about every 3 days.
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| − | ** Parietal cells and zymogen cells are produced at a slower rate; the parietal cells have a half-life of 23 days.
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| − | ===Defence Mechanisms===
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| − | # Secretions :
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| − | #* Mucus (inhibits contact with mucosa, protects surface).
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| − | #* Acid (parietal cells)
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| − | #* Digestive enzymes (pepsin from gastric chief cells)
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| − | # Epithelium:
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| − | #* Provides a barrier
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| − | #** Stratified squamous epithelium; multilayered, high cell turnover
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| − | # Movement:
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| − | #* Continuous movement discourages persistence of insult at mucosa.
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| | ===[[Stomach and Abomasum Inflammation - Pathology|Inflammatory Conditions]]=== | | ===[[Stomach and Abomasum Inflammation - Pathology|Inflammatory Conditions]]=== |
| | ===[[Stomach and Abomasum Proliferative - Pathology|Proliferative Pathology]]=== | | ===[[Stomach and Abomasum Proliferative - Pathology|Proliferative Pathology]]=== |