The cochlea is a part of the inner ear that is responsible for hearing. It is a spiral-shaped cavity in the bony labyrinth and is filled with fluid. The cochlea is divided into three sections: the scala vestibuli, the scala media, and the scala tympani. The scala vestibuli and scala tympani are connected by the helicotrema, while the scala media is filled with endolymphatic fluid. The cochlea is lined with thousands of tiny hair cells that detect sound vibrations and convert them into electrical signals that are sent to the brain.