Which statement describes the first step when blood is diluted with water?

Which statement describes the first step when blood is diluted with water?

• A. From plasma space to interstitial space.
• B. From interstitial space to plasma space.
• C. From plasma directly to cells.
• D. There is no fluid movement.

Answer: (A)

When blood is diluted with water, plasma osmolarity and oncotic pressure drop. Water then moves by osmosis from the intravascular space into the surrounding interstitial space, because the plasma becomes hypotonic relative to the interstitial fluid. This initial shift describes fluid moving from plasma space to interstitial space, rather than into cells or staying put.

When blood is diluted with water, plasma osmolarity and oncotic pressure drop. Water then moves by osmosis from the intravascular space into the surrounding interstitial space, because the plasma becomes hypotonic relative to the interstitial fluid. This initial shift describes fluid moving from plasma space to interstitial space, rather than into cells or staying put.