semicircular canals


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semicircular

 [sem″e-ser´ku-lar]
shaped like a half-circle.
semicircular canals the passages in the bony labyrinth of the inner ear that control the sense of equilibrium. Each ear has three semicircular canals (anterior, lateral, and posterior), at approximately right angles to each other, which are filled with fluid and have ampullae (enlarged portions) at one end that contain nerve endings. (See also Plates.)

The semicircular canals respond to movement of the head. When the head changes position in any direction, the fluid in the canal that lies in the plane of movement also moves, but because of its inertia the fluid flow lags behind the head movement. Thus the fluid presses against the delicate hairs of the nerves in the ampulla, and the nerves then register the fact that the head is turning in a given direction so that the body can seek to maintain its equilibrium.

It is the fluid movement in the semicircular canals that causes the feeling of dizziness or vertigo after spinning. When the spinning stops, the fluid in the horizontal canal continues to move for a moment in the direction of the spin, giving a temporary false reading that the head is turning in the other direction. motion sickness is caused by the unusual and erratic motions of the head in an airplane, car, or ship, and the resulting stimulation of the semicircular canals.

semicircular canals (of bony labyrinth)

[TA]
the organ of balance; the three bony tubes of the labyrinth of the inner ear within which the membranous semicircular ducts are located; they lie in planes at right angles to each other and are known as anterior semicircular canal [TA] (canalis semicircularis anterioris [TA]), posterior semicircular canal [TA] (canalis semicircularis posterioris [TA]), and lateral semicircular canal [TA] (canalis semicircularis lateralis [TA]).

semicircular canals

The three tubular structures of the labyrinth of the inner ear, which lie in three different planes and which contain fluid. Movement of the head leads to differential stimulation of nerve endings within the canals and provides the brain with information about orientation.

semicircular canals

the fluid-filled canals present in the inner ear of vertebrates. Usually there are three canals on each side of the head, one in each plane - two vertical and at right angles to each other, and one horizontal and at right angles to the other two. Any movement causes the fluid in the canals to stimulate the receptors (see CRISTA AMPULLARIS) in the AMPULLA at the end of each canal, so that the group of semicircular canals is sensitive to the movements of the head and serves to maintain BALANCE.
References in periodicals archive ?
Focal sclerosis of semicircular canals with severe DFNA9 hearing impairment caused by a P51S COCH-mutation: is there a link?
In addition, the locations of the fistulas were recorded as lateral semicircular, posterior, superior semicircular canal, round window, or cochlea-vestibule.
The horizontal head impulse test (HIT) was developed by Halmagyi and Curthoys as a measure of vestibular semicircular canal function.
Dehiscence or thinning of bone overlying the superior semicircular canal in a temporal bone survey.
Radiological signs indicating cholesteatoma in the attic included erosion or destruction of scutum or spur (the lateral wall of the attic), widening of the aditus ad antrum (loss of figure of "8" appearance) , antral wall erosions and widening , ossicular erosions and destruction , medial attic wall erosion which may lead to facial nerve canal involvement, which may cause paresis or paralysis , erosion of the lateral semicircular canal which may result into fistula formation (Figure 1), dehiscence of tegmen tympani , dehiscence of sigmoid sinus plate, erosion of the external auditory canal (EAC), and automastoidectomy.
Rotational vertigo is seen in patients with diseases of the semicircular canals or their central connections, or damage to the otoliths resulting in linear vertiginous sensations or illusions of body tilt.
In 72 of 313 (23%) semicircular canals were found to be malformed.
In recent years, many researchers have focused on whether the caloric test can evaluate the function of vertical semicircular canals. Yagi et al.
To work out if you are moving, the brain relies on information sent by the semicircular canals. They contain fluid which sloshes around in the canals as you move.
The bony labyrinth of the inner ear is made up of the cochlea, the major organ of hearing, the vestibule and the three semicircular canals which sense head motion and provide input to synchronize movement with visual stimuli.
With T2-weighted image it is possible to assess the cochlea, the semicircular canals, the internal acoustic meatus and the cerebello-pontine angle.
A second example of Riche's cruel streak is the demise of Elliot's boss, Victor Rainblatt, who suffers from a lack of balance due to the fact that his "semicircular canals no longer ...