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GASTROINTESTINAL PHYSIOLOGY Overvievv of Cii Trać! Fluid and Electrolyte Transport

Ingest

2000 ml/day HjO

Duodenum (HCOj^- secretion)

Saliva

1500 ml/day

Amino

adds,

glucosc

lleum and Jejunum (NaCl reabsorplion)

—100 ml/day I GO excreted

(NaCl reabsorplion and K' secretion)

|. Perkins

°WBN

Figurę 7.34 Cl Tract Fluid and Electroiyte Transport

Large volumes of fluid aro sec reted and absorbed by the Cl tract eath day. The secreted fluid helps maintain the intestinal contents in a liq-uefied State to aid digestion. Normally, this secreted fluid, along with any fluid ingested, is absorbed so that only 100 mL/day of water is exireted in the feces (with diarrhea, intestinal fluid loss can reach 20 l /day). Both the secretion of lluid and its absorption are diiven by electrolyte transport. Secretion of NaCl drives fluid secretion, wherea: the absorption of Na* with Cl and other solutes drives absorption. The principal cellular mechanisms of intestinal electrolyte transport are illustratod. For simplicity, not all known mechanisms are shown. Also, cells may express mulliple transport Systems, which here are depicted as being present in diffcrent cells.

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