1' Prior to the vertical osmotic

1
Creation and Maintenance of the Medullary Osmotic
Gradient
300
1. Prior to the vertical osmotic gradient
being established, ISF lumen 300
mosm/L
300 300 300 300 300
300 300 300 300
2. Movement of solutes out of the ascending
limb lumen creates localized 200 mosm/L
gradients ? H2O cannot follow
3. Net diffusion of H2O occurs by osmosis out
of the descending limb into the ISF until the
osmo- larities of the 2 fluids equilibrate
(Fig. 14-28)