semicircular canals


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Related to semicircular canals: utricle

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.

semicircular

shaped like a half-circle.

semicircular canals
the passages in the inner ear, in the bony labyrinth concerned with the sense of balance, especially the detection of movement. Each ear has three semicircular canals (anterior, lateral and posterior) situated approximately at right angles to each other. They contain the semicircular ducts.
semicircular ducts
the membranous tubes housed within the semicircular canals.They have enlarged portions at one end, called ampullae, which contain nerve endings, and which are filled with fluid.
The semicircular ducts respond to movement of the head. When the head changes position, the fluid in the duct 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 these nerves then register the fact that the head is turning in such a direction.
It is the fluid movement in the semicircular ducts 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 ducts. Many animals, even fish, can experience motion sickness.
References in periodicals archive ?
Previous research showed that there is a direct relationship between the size of the semicircular canals and the degree of agility an animal exhibits.
9) In their review, these defects were usually located in the external wall of the superior semicircular canal.
Bilateral posterior semicircular canal dehiscences were identified (figure).
The tumor had invaded the internal auditory canal below the superior semicircular canal, and it extended anteriorly to the carotid artery.
The disadvantage of ENG is that it evaluates primarily the function of the lateral semicircular canals.
8) This maneuver was designed to cause the free canaliths to migrate by gravitation from the posterior semicircular canal to the utricle, where they would no longer interfere with the dynamics of the semicircular canals.
Displacement of calcite fragments from the degenerating otoconia into the semicircular canals is known to be responsible for this process.
The vein of the paravestibular canaliculus (VPVC) runs parallel to the endolymphatic duct and drains the major portion of the semicircular canals and part of the utricle.
Following absorption of the drops through the round window membrane, gentamicin has to travel from the basal turn of the cochlea and through all its turns before it reaches the neuroepithelium of the otolithic organs and the semicircular canals in the vestibule where it does its damage.
CT is used in the preoperative assessment of possible cochlear implantation because it can detect sclerosis, irregularity, or obliteration of the cochlea, vestibule, and semicircular canals.
It covers a larger portion of the dynamic range of the semicircular canals than the caloric stimuli.
Head angular velocity is measured by the cristae of the semicircular canals, while the maculae of the statolabyrinth (utricle and saccule) register linear acceleration and changes in the gravitational force.