endolymfa

Endolymfa is a term used to refer to the endolymph, the fluid contained within the membranous labyrinth of the inner ear. It fills the cochlear duct (scala media) and the vestibular organs, bathing the sensory hair cells that detect sound and head movement.

The composition of endolymfa is distinct from surrounding fluids, being rich in potassium and low in sodium. This ionic makeup helps create a strong electrochemical gradient, and the stria vascularis actively maintains the endolymphatic environment and generates an endolympha potential of about +80 millivolts relative to surrounding fluids. This electrical environment is crucial for the proper transduction of mechanical stimuli into neural signals.

Functionally, endolymfa provides the ion availability necessary for hair cell receptors to function. When stereocilia on hair cells are deflected, ion channels open and potassium influx from the endolymph contributes to receptor potential changes that initiate neural signaling for hearing and balance. The delicate maintenance of endolympha is drawn from the activity of the outer structures in the inner ear and is essential for normal sensory processing.

Clinical relevance arises when endolymphatic homeostasis is disturbed. Endolympha imbalance can lead to endolymphatic hydrops, a condition associated with Meniere’s disease, characterized by vertigo, tinnitus, and fluctuating hearing loss. Other inner ear disorders may involve impaired ion transport or flow within the endolymphatic system, underscoring its role in auditory and vestibular health.