<Li> Potassium (K) 3.4--5.2 mM </Li> <Li> Calcium (Ca) 1.4--1.5 mM </Li> <P> Main anions: </P> <Ul> <Li> Chloride (Cl) 99--110 mM </Li> <Li> Bicarbonate (HCO) 22--28 mM </Li> <Li> Phosphate (HPO) 0.8 - 1.4 mM </Li> </Ul>

Fluid exchange mainly occurs in which of the following