The membranous labyrinth, also known as the inner ear, is responsible for our hearing and sense of balance. There are several synonyms for this complex structure, including the cochlear duct, vestibular labyrinth, and semicircular canals. The cochlear duct is the spiral-shaped tube of the inner ear that contains the sensory cells responsible for detecting sound. The vestibular labyrinth includes the utricle and saccule, which help us maintain our balance and sense position in space. Finally, the semicircular canals are three fluid-filled tubes that detect rotational movements. Understanding these different components of the membranous labyrinth is crucial for diagnosing and treating hearing and balance disorders.