What does endolymph mean?
Endolymph is the specialized fluid found inside the membranous labyrinth of the inner ear, filling both the cochlea, where sound is detected, and the vestibular organs, which govern balance. Chemically distinctive for its high potassium and low sodium content — the reverse of most extracellular fluids — endolymph carries an electrical charge that helps drive the conversion of motion into nerve signals. When sound waves or head movements disturb it, sensory hair cells are deflected and translated into impulses the brain interprets as hearing or spatial orientation. Because disturbances in this fluid can cause dizziness, tinnitus, or hearing loss, endolymph figures prominently in medicine: conditions such as Ménière's disease are associated with abnormal accumulation known as endolymphatic hydrops. The word derives from Greek roots meaning "within" plus "lymph," and appears chiefly in anatomical, audiological, and clinical contexts.
nounThe clear, potassium-rich fluid contained within the membranous labyrinth of the inner ear, filling the cochlear and vestibular structures.
- The fluid within the membranous labyrinth of the inner ear (the cochlea and the vestibular organs), essential for hearing and balance.
"A buildup of endolymph in the inner ear can produce the vertigo characteristic of Ménière's disease."
"Movement of the endolymph over hair cells in the semicircular canals signals rotation of the head to the brain."
"Endolymphatic hydrops — an abnormal accumulation of endolymph — is thought to underlie the symptoms of Ménière's disease."
Rarely pluralized; the plural appears mainly when discussing fluids from different individuals or species.
"The researchers compared endolymphs sampled from several mammalian species."
Your sense of balance literally floats on a fluid called endolymph — and its unusual potassium-rich chemistry is unlike almost any other body fluid.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of endolymph
The term combines the Greek prefix "endo-" ("within") with "lymph," itself from Latin "lympha" meaning clear water, ultimately from Greek. It was coined in the nineteenth century as anatomists distinguished the fluid inside the inner ear's membranes from the surrounding perilymph, whose name uses the parallel Greek prefix "peri-" ("around"). Cognates sharing these roots include "endocrine" and "endoderm" on one side and "lymphatic" on the other.
How endolymph is actually used
Strictly a technical term used in anatomy, otology, and audiology; it rarely appears outside medical or scientific writing. The related adjective is "endolymphatic."
Easily confused with endolymph
Perilymph is the separate fluid in the inner ear that surrounds the membranous labyrinth, whereas endolymph fills the inside of it.