Absorption mechanisms · Physiology

Water absorption in the small intestine is 'isostatic.' This means that:

  1. Water is actively pumped across the apical membrane
  2. Water follows solute absorption to keep osmotic equilibrium
  3. Water absorption is entirely independent of sodium transport
  4. Water moves only through the transcellular pathway
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Correct answer: Water follows solute absorption to keep osmotic equilibrium

The intestinal mucosa is highly permeable to water. As solutes (like glucose and $Na^+$) are actively transported into the lateral intercellular spaces, they create an osmotic gradient that pulls water along passively.

Difficulty: Medium Question 34 of 40

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