The scala media (cochlear duct) is separated from the scala vestibuli by Reissner's membrane and from the scala tympani by the basilar membrane. The endolymph within the scala media has an unusually high potassium concentration of approximately 150 mEq/L. Which structure is primarily responsible for maintaining this high K+ concentration?

• A Organ of Corti hair cells
• B Spiral ligament type I fibrocytes
• C Reissner's membrane
• D Stria vascularis ✓

Explanation

The stria vascularis is a specialized highly vascularized epithelial layer on the lateral wall of the cochlear duct responsible for secreting K+-rich endolymph and maintaining the +80 mV endocochlear potential (EP). It contains marginal cells with high Na/K-ATPase activity and K+ channels that actively pump K+ into the endolymph. The spiral ligament fibrocytes form the K+ recycling pathway that returns K+ from the perilymph back to the stria vascularis. Mutations in connexins (Cx26/Cx30) disrupt this K+ recycling and cause hereditary SNHL.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.