Fluid and Electrolyte Transport
Start with the big picture
The lesson follows transport by substance and intestinal segment. Sodium absorption uses nutrient cotransport in the jejunum and sodium–hydrogen exchange and aldosterone-sensitive channels in the ileum and colon. Chloride may follow sodium or be exchanged for bicarbonate, while crypt cells secrete chloride through CFTR. Potassium is absorbed in the small intestine and can be secreted by the colon. Bicarbonate secretion helps neutralize acid in the duodenum; bicarbonate absorption and hydrogen-ion secretion are also covered. Water follows solute absorption through transcellular and paracellular routes. The final section distinguishes secretory, osmotic, and inflammatory diarrhea by their mechanisms and features, including whether fasting affects the diarrhea and whether blood or leukocytes are present.
What you'll learn
- Describe sodium absorption mechanisms in the jejunum, ileum, and colon.
- Explain how chloride and potassium are absorbed or secreted along the gut.
- Summarize bicarbonate and hydrogen-ion transport in the intestine.
- Identify the main routes of water movement across the intestinal lining.
- Distinguish secretory, osmotic, and inflammatory diarrhea by their features.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
