Macula of saccule

The saccule is the smaller of the two vestibular sacs; it is globular in form, and lies in the recessus sphæricus near the opening of the scala vestibuli of the cochlea. Its anterior part exhibits an oval thickening, the macula of saccule (or saccular macula), to which are distributed the saccular filaments of the acoustic nerve.

The macula of saccule lies in a nearly vertical position. Its function is to detect vertical linear acceleration. It is a 2 mm by 3mm patch of hair cells. Each hair cell of the macula contains 40 to 70 stereocilia and one true cilia, called a kinocilium. A gelatinous cover called the otolithic membrane envelops the tips of the stereocilia and kinocilium. The otolithic membrane is weighted with small protein-calcium carbonate granules called otoliths.

In vertical linear acceleration, the weighted otolithic membrane lags behind the stereocilia and kinocilium. This bends the stereocilia, which is interpreted by the brain as vertical linear acceleration.

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This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.