The Physiology of Gastric Secretions 3
January 27th 2010 16:20
The Stomach
The main site of pathology in acid-peptic diseases is the stomach. It is therefore the site of action of the antacids used in treating these disorders. It is indeed important to know how stomach contributes in the chemical digestion of food. What are the glands in the stomach involved in the process? What specific substances are they secreting? What are the stimuli and the mechanisms involved in the release and regulation of these secretions? How does an excess of these secretions contribute to the development of acid-peptic disorders?
functionally, the stomach can be divided into (1) the orad portion, comprising the first two-third of the body; and (2) the caudal portion, comprising the remainder of the body plus the antrum. The functional divisions of the stomach play role in the mechanical digestive process.
Hydrochloric Acid Secretion
As stated earlier, one of the primary sources of increased acidity in the stomach is the hydrochloric acid produced in the gastric lumen. It is therefore necessary to review how hydrochloric acid is produced:
1. Chloride ion is actively transported from the cytoplasm of the parietal cell into the lumen. Sodium ions are also actively transported out. These events create a negative potential in the canaliculus, which in turn causes diffusion of positively charged potassium.
2. Water dissociates into hydrogen ion and hydroxyl ion in the cytoplasm. The hydrogen ions are then actively secreted into the lumen in exchange for potassium (catalyzed by H , K , ATPase). Sodium ions are also actively reabsorbed.
3. Bottomline is that when K and Na were reabsorbed, the lumen gets H in exchange. This proton combines with Cl-, forming HCl.
The main site of pathology in acid-peptic diseases is the stomach. It is therefore the site of action of the antacids used in treating these disorders. It is indeed important to know how stomach contributes in the chemical digestion of food. What are the glands in the stomach involved in the process? What specific substances are they secreting? What are the stimuli and the mechanisms involved in the release and regulation of these secretions? How does an excess of these secretions contribute to the development of acid-peptic disorders?
functionally, the stomach can be divided into (1) the orad portion, comprising the first two-third of the body; and (2) the caudal portion, comprising the remainder of the body plus the antrum. The functional divisions of the stomach play role in the mechanical digestive process.
Hydrochloric Acid Secretion
As stated earlier, one of the primary sources of increased acidity in the stomach is the hydrochloric acid produced in the gastric lumen. It is therefore necessary to review how hydrochloric acid is produced:
1. Chloride ion is actively transported from the cytoplasm of the parietal cell into the lumen. Sodium ions are also actively transported out. These events create a negative potential in the canaliculus, which in turn causes diffusion of positively charged potassium.
2. Water dissociates into hydrogen ion and hydroxyl ion in the cytoplasm. The hydrogen ions are then actively secreted into the lumen in exchange for potassium (catalyzed by H , K , ATPase). Sodium ions are also actively reabsorbed.
3. Bottomline is that when K and Na were reabsorbed, the lumen gets H in exchange. This proton combines with Cl-, forming HCl.
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