Total body water sits in two big pools. Intracellular (ICF) is 2/3 of it. That water is inside the cells and high in potassium. Extracellular (ECF) is 1/3. That water is outside the cells and high in sodium. The ECF splits again into three parts. Click each compartment.
The water map
The bar is all of your body water. The left side is inside the cells. The right side is outside them, split three ways. Note which ion rules each part.
Pick a compartment to explore.
Pick a compartmentICF and the 3 parts of ECF
What it is
The big two:ICF holds 2/3 of body water, and its main ion is potassium (K⁺). ECF holds 1/3, and its main ion is sodium (Na⁺). Remember that water follows sodium. Wherever Na⁺ goes, water shifts too.