INTERNAL EAR, DRAWING. INTERNAL EAR, DRAWING Inner ear and vestibular system. The inner ear is the organ of audition and balance. It is composed of two parts : the bony labyrinth, externally, that corresponds to a series of cavities excavated in the temporal bone, and the membranous labyrinth, internally. The bony labyrinth divids into three regions : semi_circular canals on the left of the image, the vestibule at the centre and the cochlea in shape of snail shell. The three semi_circular canals