| VC | vitelline coat |
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| VE | vitelline envelope |
| attraction sphere | A set of radiating microtubules extending outward from the cytocentrum and centrosphere of a dividing cell. Synonym: aster, attraction sphere, Lavdovsky's nucleoid, paranuclear body. Origin: G. Astron, star, + sphaira, ball (05 Mar 2000) |
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| sphere | 1. <geometry> A body or space contained under a single surface, which in every part is equally distant from a point within called its center. 2. Hence, any globe or globular body, especially a celestial one, as the sun, a planet, or the earth. "Of celestial bodies, first the sun, A mighty sphere, he framed." (Milton) 3. <astronomy> The apparent surface of the heavens, which is assumed to be spherical and everywhere equally distant, in which the heavenly bodies appear to have their places, and on which the various astronomical circles, as of right ascension and declination, the equator, ecliptic, etc, are conceived to be drawn; an ideal geometrical sphere, with the astronomical and geographical circles in their proper positions on it. In ancient astronomy, one of the concentric and eccentric revolving spherical transparent shells in which the stars, sun, planets, and moon were supposed to be set, and by which they were carried, in such a manner as to produce their apparent motions. 4. <logic> The extension of a general conception, or the totality of the individuals or species to which it may be applied. 5. Circuit or range of action, knowledge, or influence; compass; province; employment; place of existence. "To be called into a huge sphere, and not to be seen to move in 't." (Shak) "Taking her out of the ordinary relations with humanity, and inclosing her in a sphere by herself." (Hawthorne) "Each in his hidden sphere of joy or woe Our hermit spirits dwell." (Keble) 6. Rank; order of society; social positions. 7. An orbit, as of a star; a socket. Armillary sphere, Crystalline sphere, Oblique sphere,. See Armillary, Crystalline,. Doctrine of the sphere, applications of the principles of spherical trigonometry to the properties and relations of the circles of the sphere, and the problems connected with them, in astronomy and geography, as to the latitudes and longitudes, distance and bearing, of places on the earth, and the right ascension and declination, altitude and azimuth, rising and setting, etc, of the heavenly bodies; spherical geometry. Music of the spheres. See Music. Synonym: Globe, orb, circle. See Globe. Origin: OE. Spere, OF. Espere, F. Sphere, L. Sphaera,. Gr. A sphere, a ball. Source: Websters Dictionary (01 Mar 1998) |
| debye sphere | <radiobiology> Sphere around a charged test particle whose radius is equal to the Debye length. (09 Oct 1997) |
| vitelline | <biology> Of or pertaining to the yolk of eggs; as, the vitelline membrane, a smooth, transparent membrane surrounding the vitellus. Origin: L. Vitellus the yolk of an egg. Source: Websters Dictionary (01 Mar 1998) |
| vitelline artery | <anatomy, artery> An artery carrying blood to the yolk sac from the embryo. Synonym: arteria vitellina. (05 Mar 2000) |
| vitelline cord | A persistent yolk stalk in the form of a solid cord of tissue connecting ileum to umbilicus. Synonym: omphalomesenteric cord. (05 Mar 2000) |
| vitelline duct | The narrow tube connecting the yolk sac with the midgut of the embryo; persistence of all or part of it in post-foetal life produces abnormalities, of which the commonest is meckel's diverticulum. (12 Dec 1998) |
| vitelline fistula | A fistula between the umbilicus and the terminal ileum along the course of a persistent vitelline cord. See: Meckel's diverticulum. (05 Mar 2000) |
| vitelline layer of egg | <zoology> The membrane, usually of protein fibres, immediately outside the plasmalemma of the ovum and the earlier stages of the developing embryo. Its structure and composition vary in differing animal groups. (18 Nov 1997) |
| vitelline membrane | <cell biology> The plasma membrane of the egg. (12 Dec 1998) |
| Vitelline pole | <embryology> The vegetative pole of an ovum. (05 Mar 2000) |
| vitelline reservoir | In cestodes and trematodes, a common chamber receiving vitelline (yolk) material from the two vitelline ducts; the yolk material then passes into the ootype to surround the ovum with nutritive vitelline granules that are enclosed by a characteristically formed eggshell. Synonym: vitelline reservoir. (05 Mar 2000) |
| vitelline sac | <embryology, ornithology> One of the set of extra embryonic membranes, growing out from the gut over the yolk surface, in birds formed from the splanchnopleure, an outer layer of splanchnic mesoderm and an inner layer of endoderm. (18 Nov 1997) |
| vitelline vein | <anatomy, vein> A vein returning blood from the yolk sac to the embryo. Synonym: vena vitellina. (05 Mar 2000) |
| vitelline vessels | See: vitelline artery, vitelline vein. (05 Mar 2000) |
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