Extracellular and Intracellular fluid

Feature

Extracellular Fluid (ECF)

Intracellular Fluid (ICF)

Location

Outside the cells

Inside the cells

Volume

~20% of total body weight
(~15L in a 70 kg adult)

~40% of total body weight
(~28L in a 70 kg adult)

Main Cation

Sodium (Na+)

Potassium (K+)

Main Anion

Chloride (Cl-) > Bicarbonate (HCO3)

Phosphate (PO4) and Proteins
(negatively charged)

pH

~7.4 (slightly alkaline)

~7.0 (neutral)

Protein Content

Low (except in plasma)

High (inside the cell cytoplasm)

Osmolality

~290 mOsm/kg

~290 mOsm/kg
(osmotic equilibrium with ECF)

Subdivisions

- Interstitial fluid (surrounds cells)

- Plasma (intravascular fluid)

Not subdivided

Glucose
Concentration

High

Low (utilized for energy)