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Gaslric Secretion: II

GASTROINTESTINAL PHYSIOLOGY

Secrelions of gastric acid (H* ) by parietal celi mediated by neurocrine, paracrine, and endocrine mechanisms. Medical or surgicał blockade of these mechanisms affords therapeutk options

Parielal celi mechanisms of acid lH^r) secretion involve senes of Chemical exchanges across basal membranę, wilh finał active exrhange of H* for K* mediated across apical (secretory) membranę by H'-K⁺ ATPase (proton pump)

R.ite uf secretion (mLymini

Gastric fluid ion conceniralion ; a function of gastric secretion ra>

The parietal cells secretes HCl via an H -K -ATPase (H^ pump). Car-bonic anhydrase within the parietal cells catalyzes the hydration of CO* and ultimately the production of H'. The parietal cell is stimu-lated to secrete HCl by vagal efferent fibers (parasympathetic), gas-trin, and histaminę. Gastrin is produced and released trorn neuroen-docrine G cells. The enterochromaffin-like cells (ECL cellsl releast-histamine, włiich acls synergistically with acetylcholine and gastrir stiinulate secretion. Somatostatiri produced by neuroendocrine D cells (not shown) acts on the G cell to inhibit gastrin release.