The helicotrema allows communication between which two scalae at the apex?

The helicotrema allows communication between which two scalae at the apex?

• A. Scala media and scala tympani
• B. Scala vestibuli and scala tympani
• C. Scala vestibuli and scala media
• D. Endolymphatic sac and perilymphatic space

Answer: (B)

The helicotrema is the small passage at the cochlear apex that directly links scala vestibuli and scala tympani, allowing perilymph to flow between these two compartments. This apical connection does not involve the scala media, which is separated by Reissner’s membrane and the basilar membrane. Because SV and ST can exchange fluid through the helicotrema, low-frequency pressure waves can travel to the apex and influence the basilar membrane there, while higher-frequency components primarily interact along the length of the cochlea before reaching the apex. The other options describe connections that aren’t present: scala media is not directly connected to the perilymph-filled vestibuli or tympani via the helicotrema, and the endolymphatic sac is not a direct channel between scalae.

The helicotrema is the small passage at the cochlear apex that directly links scala vestibuli and scala tympani, allowing perilymph to flow between these two compartments. This apical connection does not involve the scala media, which is separated by Reissner’s membrane and the basilar membrane. Because SV and ST can exchange fluid through the helicotrema, low-frequency pressure waves can travel to the apex and influence the basilar membrane there, while higher-frequency components primarily interact along the length of the cochlea before reaching the apex. The other options describe connections that aren’t present: scala media is not directly connected to the perilymph-filled vestibuli or tympani via the helicotrema, and the endolymphatic sac is not a direct channel between scalae.