The saccule (Latin: sacculus) is a bed of sensory cells in the inner ear that detects linear acceleration and head tilting in the vertical plane, and converts these vibrations into electrical impulses to be interpreted by the brain.

The vestibule is the name of the fluid-filled, membranous duct that contains these organs of balance and is in turn encased in the temporal bone of the skull as a part of the inner ear.

This duct is joined by the ductus utriculosaccularis, and then passes along the aquæductus vestibuli and ends in a blind pouch saccus endolymphaticus (endolymphatic sac) on the posterior surface of the petrous portion of the temporal bone, where it is in contact with the dura mater.

From the lower part of the saccule a short tube, the canalis reuniens of Hensen, passes downward and opens into the ductus cochlearis near its vestibular extremity.

cVEMP amplitude is linearly dependent upon stimulus intensity and is most reliably elicited with a loud (generally at or above 95 dB nHL) click or tone burst.

This myogenic potential is felt to assess saccular function, because the response is present in completely deafened ears and because it is routed through the inferior vestibular nerve, which is known to dominantly innervate the saccule.

[5] Research suggests that in vertebrate evolution, sensory cells became specialized as gravistatic sensors after they became assembled to form the ear.

Novel directions of differentiation were apparently further expanded by incorporating unique molecular modules in newly developed sensory epithelia.

For example, the saccule gave rise to the auditory epithelium and corresponding neuronal population of tetrapods, starting possibly in an aquatic environment.