semicircular ducts


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Related to semicircular ducts: utricle

sem·i·cir·cu·lar ducts

[TA]
three small membranous tubes of the vestibular labyrinth within the bony semicircular canals of the bony labyrinth that form loops of about two thirds of a circle. The three semicircular ducts: anterior semicircular duct [TA] (ductus semicircularis anterior [TA]), lateral semicircular duct [TA] (ductus semicircularis lateralis [TA]), and posterior semicircular duct [TA] (ductus semicircularis posterior [TA])-lie in planes at right angles to each other and open into the vestibule by five openings of which one is common to the anterior and lateral ducts. Each duct has an ampulla at one end within which filaments of the vestibular nerve terminate.
Synonym(s): ductus semicirculares [TA]

sem·i·cir·cu·lar ducts

(sem'ē-sĭr'kyū-lăr dŭkts) [TA]
Three small, membranous tubes in the bony semicircular canals that lie within the bony labyrinth and form loops of about two thirds of a circle. The three (anterior semicircular duct, lateral semicircular duct, and posterior semicircular duct) lie in planes at right angles to each other and open into the vestibule by five openings, of which one is common to the anterior and lateral ducts. Each duct has an ampulla at one end within which filaments of the vestibular nerve terminate.

sem·i·cir·cu·lar ducts

(sem'ē-sĭr'kyū-lăr dŭkts) [TA]
Three small membranous tubes of the vestibular labyrinth within the bony semicircular canals of the bony labyrinth that form loops of about two thirds of a circle.

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.