| Utricle (ear) | |
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| illustration of otolith organs showing detail of utricle, otoconia, endolymph, cupula, macula, hair cell filaments, and saccular nerve | |
| Components of the inner ear including the utricle | |
| Latin | utriculus |
| Gray's | subject #232 1051 |
| MeSH | Saccule+and+Utricle |
The utricle, or utriculus, along with the saccule is one of the two otolith organs located in the vertebrate inner ear. These use small stones and a viscous fluid to stimulate hair cells to detect motion and orientation.
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Contents
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Anatomy
The utricle is larger than 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 which, due to gravity, pull on the cilia and tilt them. 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. The effect of this is that, for example, an individual lying down to sleep will continue to detect that they are lying down hours later when they awaken.
That portion which is lodged in the recess forms a 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.
The ductus utriculosaccularis comes off of the anterior wall of the utricle and opens into the ductus endolymphaticus.
See also
Additional images
 Vestibular system |
 Transverse section through head of fetal sheep, in the region of the labyrinth. X 30. |
 The membranous labyrinth. |
External links
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 As such, some of the information contained within it may be outdated.
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