In a surgery for gastric hypersecretion, which structure's alteration reduces stomach acid production?

The vagus nerve plays a crucial role in the regulation of gastric acid secretion. It is part of the parasympathetic nervous system and stimulates gastric secretions by releasing neurotransmitters that signal the gastric parietal cells to produce hydrochloric acid. When the vagus nerve is altered, either through surgical manipulation or other means, this stimulation is reduced, leading to lower stomach acid production.

In the context of gastric hypersecretion, targeting the vagus nerve is an effective approach, as it directly influences the production of gastric acid from the stomach lining. This can help in managing conditions associated with excessive stomach acid, such as peptic ulcers or gastroesophageal reflux disease.

The other structures listed do not have a direct role in the control of acid secretion in the stomach. For instance, the portal vein is involved in the blood supply and nutrient transport to the liver; the celiac artery supplies blood to various abdominal organs but does not directly influence acid secretion; and the pyloric valve regulates the passage of stomach contents into the small intestine rather than modulating acid production.