Comparative Concentrations of Major Body Fluids with units
Values in millimolar (mM) unless labeled otherwise; rounded typical mammalian references [1–6].
| Ion / Substance (Unit) | ICF (Typical Cell) | ECF (Plasma / ISF) | CSF | Brain ISF | Perilymph | Endolymph |
|---|---|---|---|---|---|---|
| Na⁺ (mM) | 10–15 | 135–145 | 145–150 | ~145 | ~150 | 1–2 |
| K⁺ (mM) | 120–150 | 3.5–5 | 2.5–3 | ~3 | ~5 | ~150 |
| Cl⁻ (mM) | 4–10 | 95–105 | 120–130 | ~120 | ~120 | 20–30 |
| Ca²⁺ (free, mM) | 0.0001 | 1.2 | 1.1 | ~1.1 | ~1.3 | ~0.02 |
| Mg²⁺ (mM) | 10–30 | 0.8–1 | ~1.0 | ~1 | ~1 | ~1 |
| HCO₃⁻ (mM) | 10–15 | 22–28 | 22–26 | ~25 | ~25 | ~25 |
| Proteins (mM / g·L⁻¹) | 65–100 mM | ~1 mM (plasma) | very low (~0.15 g·L⁻¹) | very low | negligible | negligible |
| Glucose (mM) | <1 | ~5 | 3–4 | ~3–4 | ~5 | very low |
| pH (unitless) | 7.0–7.2 | 7.35–7.45 | ~7.33 | ~7.3 | ~7.4 | ~7.4 |
Notes: Values are rounded typical ranges for healthy mammals and can vary with species, age, sampling site, and physiological state.
CSF/ISF protein is much lower than plasma. Endolymph is a K⁺-rich extracellular fluid that underlies the positive endocochlear potential.
References (Vancouver style)
- Hall JE. Guyton and Hall Textbook of Medical Physiology. 14th ed. Philadelphia: Elsevier; 2021.
- Boron WF, Boulpaep EL. Medical Physiology. 3rd ed. Philadelphia: Elsevier; 2016.
- Hladky SB, Barrand MA. Mechanisms of cerebrospinal fluid flow and exchange with blood and brain. Fluids Barriers CNS. 2014;11:26.
- Wangemann P. Supporting sensory transduction: cochlear fluid homeostasis and the endocochlear potential. Physiol Rev. 2006;86(1):187–219.
- Salt AN, Plontke SK. Endolymphatic hydrops: pathophysiology and experimental models. Otolaryngol Clin North Am. 2010;43(5):971–83.
- Nicholson C, Hrabětová S. Brain extracellular space: the final frontier of neuroscience. Biophys J. 2017;113(10):2133–42.
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