| aqueous humor | <physiology> A transparent liquid contained in the anterior and posterior chambers of the eye, produced by the ciliary process it passes to the venous system via the canal of Schlemm. (27 Sep 1997) |
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| aqueous influx phenomenon | The filling of the aqueous vein, which normally carries blood and aqueous, with aqueous, when the junction of the aqueous vein and the recipient vein is partially occluded. Synonym: Ascher's aqueous influx phenomenon. (05 Mar 2000) |
| aqueous phase | The water portion of a system consisting of two liquid phase's, one mainly water, the other a liquid immiscible with water (e.g., benzene, ether). (05 Mar 2000) |
| aqueous solution | <chemistry> A solution in which water is the dissolving medium or solvent. (09 Jan 1998) |
| aqueous vaccine | A vaccine having a liquid vehicle (e.g., physiological salt solution) as distinguished from an emulsion. (05 Mar 2000) |
| aqueous vein | <anatomy, vein> A tributary of the anterior ciliary vein which receives aqueous humor from the sinus venosus sclerae. (05 Mar 2000) |
| Ascher's aqueous influx phenomenon | The filling of the aqueous vein, which normally carries blood and aqueous, with aqueous, when the junction of the aqueous vein and the recipient vein is partially occluded. Synonym: Ascher's aqueous influx phenomenon. (05 Mar 2000) |
| blood-aqueous barrier | The anatomical mechanism that prevents exchange of materials between the chambers of the eye and the blood. The tight junctions of the nonpigmented epithelium of the ciliary body, the junctions of the iris tissues, and iris blood vessels constitute the blood-aqueous barrier. Lipid-soluble substances such as oxygen and carbon dioxide penetrate the barrier at a high rate. Sodium, larger water-soluble ions, proteins, and other large and medium-sized molecules are restricted. (12 Dec 1998) |
| white yolk | Yolk consisting of much finer particles than those of yellow yolk; thin layers of it lie between the zones of yellow yolk and form the latebra. (05 Mar 2000) |
| yellow yolk | The chief constituent of the yolk in a bird's egg; it consists of relatively coarse particles of stored food materials and is laid down in concentric zones with interposed thin layers of white yolk. (05 Mar 2000) |
| yolk | 1. The yellow part of an egg; the vitellus. 2. <zoology> An oily secretion which naturally covers the wool of sheep. <anatomy> Yolk cord, the umbilical vesicle. See Unbilical. Origin: OE. Yolke, yelke, yolke, yelke, AS. Geoloca, geoleca, fr. Geolu yellow. See Yellow Alternative forms: yelk. Source: Websters Dictionary (01 Mar 1998) |
| yolk cell | <cell biology> In those eggs in which the yolk is not distributed evenly (telolecithal eggs) the cells formed when cleavage reaches the yolk region can be termed yolk cells. (18 Nov 1997) |
| yolk cells | Primitive embryonic cell's lying between the endoderm and mesoderm; they probably give rise to the endothelium of vitelline vessels. (05 Mar 2000) |
| yolk cleavage | Segmentation of the vitellus. (05 Mar 2000) |
| yolk membrane | The membrane enveloping the yolk; specifically, the thickened cell membrane of large-yolked ova. Synonym: ovular membrane, vitelline membrane. Sometimes used to designate the zona pellucida of a mammalian ovum. Synonym: yolk membrane. (05 Mar 2000) |