Otolith

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Related to Otoconia: Epley maneuver

otolith

[′ōd·ə‚lith]
(anatomy)
A calcareous concretion on the end of a sensory hair cell in the vertebrate ear and in some invertebrates.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Otolith

 

a solid formation on the surface of the mechanoreceptor cells in the organs of equilibrium of some invertebrates and all vertebrates. Otoliths of different animals vary in origin, size, and structure: they can be secreted by cells or introduced from outside, for example, grains of sand serve as otoliths in crayfish. Mammalian otoliths are usually crystals of calcite (CaCO3) up to 10 microns (μ.) long and 1–3 μ wide.

As otoliths shift in response to acceleration and changes in body position, they mechanically irritate the underlying ciliated receptor cells, which then send appropriate signals to the brain.

The action of otoliths has been demonstrated in experiments with crayfish. The grains of sand that serve as the crayfish’s otoliths were replaced during molting by iron filings, and a magnet was placed above the animal to attract the filings. The crayfish reversed its sense of orientation, turned over, and swam with its abdomen up.

O. B. IL’INSKII

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The increase in the oVEMP amplitude on the affected side after successful repositioning procedure confirmed the hypothesis on the return of otoconia into the area of the utricular macula.
The vestibular part of the membranous labyrinth consists of three semicircular canals as anterior, posterior, and horizontal, and two otoliths as utricle and saccule; the source of the calcium carbonate crystals (otoconia) that are responsible for BPPV is the macula of the saccule (4).
The short and relatively symmetrical onset latencies we recorded with the affected and unaffected ears down in canalolithiasis imply a rapid movement of the otoconia in the horizontal canals in response of provocative testing.
The primary diagnosis on Day One of BPPV prompted using the canalith repositioning manoeuvre (CRM) described by Epley (1992) to reposition the otoconia suspected to be present in the right posterior semi-circular canal (refer to Figures 1A-1E).
(1) However, the fact that not all patients respond to the Epley maneuver (2) suggests that a different etiology is involved, and this led to the theory of cupulolithiasis, which holds that dislodged otoconia irritate the cupula.
Dizziness most likely results from damage to the middle ear (vestibular apparatus), which includes the semicircular canals that respond to rotations and the otolithic organs that respond to sense linear accelerations with otoconia crystals.
Vertigo may originate in the vestibular system, consisting of the fluid-filled semicircular canals and the utricle, hair cells topped with crystals known as otoconia. Displacement of the otoconia provides information on movement and helps the brain control your balance.
One of the most common causes is BPPV, a condition of the inner ear in which tiny calcium crystals called otoconia are dislodged from their appropriate location in the ear, which causes a sensation of vertigo or spinning.
This finding supports the premise that estrogen deficiency may contribute to the development of BPV by weakening the bond of otoconia to the utricle, they wrote.
BPPV is thought to be caused by displaced otoconia or small calcium carbonate crystals derived from a structure at the base of the inner ear called the utride.
The hair cells of the otolithic organs are blanketed with a jelly-like layer studded with tiny calcium stones called otoconia. When the head is tilted or the body position is changed with respect to gravity, the displacement of the stones causes the hair cells to bend.
This loss of otoconia occurs in the utricle but to a lesser degree than the saccule; this may be because the saccule is more susceptible due to its vertical position (Johnsson & Hawkins, 1972).