| equator | 1. <geography> The imaginary great circle on the earth's surface, everywhere equally distant from the two poles, and dividing the earth's surface into two hemispheres. 2. <astronomy> The great circle of the celestial sphere, coincident with the plane of the earth's equator; so called because when the sun is in it, the days and nights are of equal length; hence called also the equinoctial, and on maps, globes, etc, the equinoctial line. 3. <astronomy> Equator of the sun or of a planet, the great circle whose plane passes through through the center of the body, and is perpendicular to its axis of revolution. Origin: L. Aequator one who equalizes: cf. F. Equateur equator. See Equate. Source: Websters Dictionary (01 Mar 1998) |
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| equator bulbi oculi | An imaginary line encircling the globe of the eye equidistant from the anterior and posterior poles. Synonym: equator bulbi oculi. (05 Mar 2000) |
| equator lentis | The periphery of the lens lying between the two layers of the ciliary zonule. Synonym: equator lentis. (05 Mar 2000) |
| equator of eyeball | An imaginary line encircling the globe of the eye equidistant from the anterior and posterior poles. Synonym: equator bulbi oculi. (05 Mar 2000) |
| equator of lens | The periphery of the lens lying between the two layers of the ciliary zonule. Synonym: equator lentis. (05 Mar 2000) |
| aortic spindle | A fusiform dilation of the aorta immediately beyond the isthmus. Synonym: His' spindle. (05 Mar 2000) |
| central spindle | A central group of microtubules (continuous fibres) that course uninterrupted, between the asters, in contrast to the microtubules attached to the individual chromosomes (s. Fibres). (05 Mar 2000) |
| meiotic spindle | The meiotic equivalent of the mitotic spindle. (18 Nov 1997) |
| cleavage spindle | The spindle formed during the cleavage of a zygote or its blastomeres. (05 Mar 2000) |
| mitotic spindle | See: spindle and mitosis. (18 Nov 1997) |
| mitotic spindle apparatus | An organelle consisting of three components: 1) the astral microtubules, which form around each centrosome and extend to the periphery; 2) the polar microtubules which extend from one spindle pole to the equator; and 3) the kinetochore microtubules, which connect the centromeres of the various chromosomes to either centrosome. (12 Dec 1998) |
| muscle spindle | A specialised muscle fibre found in tetrapod vertebrates. A bundle of muscle fibres is innervated by sensory neurons. Stretching the muscle causes the neurons to fire, the muscle spindle thus functions as a stretch receptor. (18 Nov 1997) |
| His' spindle | A fusiform dilation of the aorta immediately beyond the isthmus. Synonym: His' spindle. (05 Mar 2000) |
| sleep spindle | The electroencephalographic record of 14-per-second bursts of wave frequency seen on EEG examination. (05 Mar 2000) |
| spindle | See: mitosis, spindle fibre. (18 Nov 1997) |