The cochlear duct (scala media) is filled with endolymph and houses the organ of Corti. The endolymph has an unusually high potassium concentration (similar to intracellular fluid). This endocochlear potential (+80 mV) is maintained by which structure?

• A Cells of the organ of Corti (inner and outer hair cells)
• B Reissner's membrane (vestibular membrane)
• C Stria vascularis on the lateral wall of the cochlear duct ✓
• D Basilar membrane fibres

Explanation

The stria vascularis is a metabolically highly active, vascularised epithelium on the lateral wall of the scala media (cochlear duct). It is responsible for actively secreting K+ into the endolymph (maintaining its high K+ concentration of ~150 mEq/L) and generating the endocochlear potential (+80 mV). This potential is the driving force for K+ influx into hair cells during mechanoelectrical transduction. Stria vascularis degeneration is the mechanism of age-related hearing loss (presbycusis) and aminoglycoside ototoxicity. Reissner's membrane simply separates the scala media from the scala vestibuli.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.