Definitions

bent ear

Utricle (ear)

The utricle, or utriculus, along with the saccule is one of the two otolith organs located in the vertebrate inner ear.

Anatomy

The utricle is larger than a grain of sand and the saccule and is of an oblong form, compressed transversely, and occupies the upper and back part of the vestibule, lying in contact with the recessus ellipticus and the part below it.

The utricle contains mechanoreceptors called hair cells that distinguish between degrees of tilting of the head, thanks to their apical cilia set-up. These are covered by otolith and, once you tilt your head, otolith viscosity has the cilia tilt as well. Depending on whether the tilt is in the direction of the kinocilium or not, the resulting hair cell polarisation is excitatory (depolarising) or inhibitory (hyperpolarisation), respectively. This signal to the vestibular nerve (which takes it to the brainstem) does not adapt with time, so if you're lying in bed, you still feel as if you're lying in bed 9 hours afterwards when you wake up.

That portion which is lodged in the recess forms a sort of pouch or cul-de-sac, the floor and anterior wall of which are thickened, and form the macula acustica utriculi, which receives the utricular filaments of the acoustic nerve.

The cavity of the utricle communicates behind with the semicircular ducts by five orifices.

From its anterior wall is given off the ductus utriculosaccularis, which opens into the ductus endolymphaticus.

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