Acidity hydrochloric acid secretion

Hypochlorhydria Hypoacidity decreased hydrochloric acid secretion by the stomach. 

Parietal (oxyntic) cells located predominantly in the body and fundus of the stomach secrete hydrochloric acid. The gastric pH is not constant owing to variation in acid secretion and gastric content. The pH in the stomach at different states of feeding and various parts of the small intestine is shown in Table 2.1. The mucus layer restricts the diffusion of hydrogen ions secreted by the intestinal epithelial cells. As a result, the pH of this 700- m-thick microclimate region is on the order 5.8 to... 

Baking soda (NaHC03) is often used as an antacid. It neutralizes excess hydrochloric acid secreted by the stomach ... 

A potassium chloride co-transporter must be closely related to the H /K -ATPase during proton secretion. Potassium and chloride ions move across the apical membrane together with secreted protons Figure 4.1) [15-17]. Potassiiun is recycled while hydrochloric acid of the gastric juice is formed by chloride ions together with the secreted protons. Stimulation of gastric acid secretion across the apical membrane may predominantly reflect the activation or insertion of an active potassium chloride co-transporter rather than direct activation of HVK -ATPase [1]. 

Fig. 2 shows the pH of various regions of the GI tract. From the slightly acidic region of the mouth, a compound enters the more acidic region of the stomach. Acidity is a consequence of hydrochloric acid secretion... 

The rate of acid secretion into the stomach is controlled by parietal cells. Acetylcholine, histamine, and gastrin are important for regulation of hydrochloric acid secretion, and they act directly on parietal cells to enhance acid secretion rate. 

The basal rate of hydrochloric acid secretion varies diurnally, being highest in the evening and lowest in the morning. After ingestion of a meal, the rate of acid secretion in the stomach increases. The three phases of increased acid secretion in response to food are the cephalic phase (before food reaches the stomach), the gastric phase (elicited by the presence of food in the stomach), and the intestinal phase (elicited by input from the duodenum and upper jejunum). 

The fasting stomach pH is about 2 to 6. In the fed state, the stomach pH is about 1.5 to 2, due to hydrochloric acid secreted by parietal cells. Stomach acid secretion is stimulated by gastrin and histamine. Mixing is intense and pressurized in the antral part of the stomach, a process of breaking down large food particles described as antral milling. Food and liquid are emptied by opening the pyloric sphincter into the duodenum... 

Large doses of caffeine can cause nausea and vomiting. Caffeine is a potent stimulant of hydrochloric acid secretion (20) and has been incriminated in exacerbating duodenal ulcers. However, decaffeinated coffee has also been reported to be as potent as instant coffee in stimulating gastric acid secretion (20). 

The stomach secretes hydrochloric acid under the influences of vagus nerve stimulation, gastrin and histamine. Histamine is the most potent stimulus of gastric acid secretion in some animal species studied, such as the horse (Kitchen et al 1998a). Histamine is released by mast cells and enterochromaffin-like cells that are immediately adjacent to the parietal cells. Histamine interacts with two distinct subsets of histamine H2 receptors on the parietal cell membrane, initiating a series of reactions that result in the phosphorylation of protein kinases and increased intracellular calcium within the parietal cell. This, in turn, results in transformation and translocation of the... 

Treatment of hypochloremia can usually be achieved with i.v. 0.9% sodium chloride, which contains more chloride relative to sodium than plasma. In horses with high-volume gastric reflux, administration of i.v. histamine H2 receptor antagonists (e.g. cimetidine at 6.6mg/kg i.v. four times a day) reduces gastric hydrochloric acid secretion and may, therefore, reduce chloride loss. In humans, i.v. hydrochloric acid has been used to treat severe hypochloremia (Kwun et al 1983) but carries substantial risks for the patient (Rothe Schimek 1986). 

The answer is d. (Murray, pp 48-62. Scriver, pp 3 5. Sack, pp 1-3. Wilson, pp 101-120.) Pepsin is secreted in a proenzyme form in the stomach. Unlike the majority of proenzymes, it is not activated by protease hydrolysis. Instead, spontaneous acid hydrolysis at pH 2 or lower converts pepsinogen to pepsin. Hydrochloric acid secreted by the stomach lining creates the acid environment. All the enzymes secreted by the pancreas are activated at the same time upon entrance into the duodenum. This is accomplished by trypsin hydrolysis of the inactive proenzymes trypsino-gen, chymotrypsinogen, procarboxypeptidase, and proelastase. Primer... 

The digestion of proteins involves the salivary glands, the gastric mucosa, and the pancreas, all which introduce digestive enzymes into the gastrointestinal tract (Chaney, in Devlin, 1986, p. 11350). These actions are assisted by hydrochloric acid secreted in the gastrointestinal tract, and by the presence of sodium chloride and sodium bicarbonate. 

One important step in the early stages of digestion is that of hydrochloric acid secretion in the stomach. In general, a 0.16 N hydrochloric acid is liberated by the parietal cells in front of a complex regulation... 

Let s consider the relative effectiveness of two antacids to illustrate how chemical calculations can be important in daily life. Baking soda, NaHC03, is often used as an antacid. It neutralizes excess hydrochloric acid secreted by the stomach. The balanced equation for the reaction is... 

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