| medial nasal primordium | An ectodermally covered mesenchymal swelling lying medial to the olfactory placode or pit in the embryo. Synonym: medial nasal fold, medial nasal primordium, medial nasal process. (05 Mar 2000) |
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| primordium | An aggregation of cells in the embryo indicating the first trace of an organ or structure. Synonym: anlage. Origin: L. Origin, fr. Primus, first, + ordior, to begin (05 Mar 2000) |
| lateral nasal primordium | An ectodermally covered mesenchymal swelling separating the embryonic olfactory pit from the developing eye. Synonym: lateral nasal fold, lateral nasal primordium, lateral nasal process. (05 Mar 2000) |
| frontonasal primordium | The unpaired embryonic prominence between the medial nasal elevations, which eventually merges with them to contribute to the bridge of the nose and the underlying nasal septum. Synonym: forebrain eminence, forebrain prominence, frontonasal primordium, frontonasal process. (05 Mar 2000) |
| axis, optic | <microscopy> The direction, or directions in an anisotropic crystal along which light is not doubly refracted. (05 Aug 1998) |
| ganglionic layer of optic nerve | <anatomy, nerve> The inner layer of multipolar neurons in the retina consisting of the relatively large neurons that give rise to the fibres of the optic nerve. Synonym: stratum ganglionare nervi optici. (05 Mar 2000) |
| vascular circle of optic nerve | <anatomy, nerve> A network of branches of the short ciliary arteries on the sclera around the point of entrance of the optic nerve. Synonym: circulus vasculosus nervi optici, circulus arteriosus halleri, circulus zinnii, Haller's circle, Zinn's corona, Zinn's vascular circle. (05 Mar 2000) |
| glioma of optic chiasm | A slow-growing tumour, usually an astrocytoma, of the optic chiasm in children. (05 Mar 2000) |
| medial root of optic tract | The smaller division of the posterior end of the optic tract that disappears under the medial geniculate body. Synonym: radix medialis tractus optici. (05 Mar 2000) |
| Graves' optic neuropathy | Visual dysfunction due to optic nerve compression in Graves' orbitopathy. (05 Mar 2000) |
| pigment epithelium of optic retina | pigmented part of retina |
| coloboma of optic nerve | <anatomy, nerve> A congenital notch in the formation of the optic nerve, appearing as a craterlike excavation at the optic disk. (05 Mar 2000) |
| postlaminar part of optic nerve | <anatomy, nerve> The portion of the optic nerve posterior to the lamina cribrosa of the sclera. Synonym: pars postlaminaris nervi optici. (05 Mar 2000) |
| prelaminar part of optic nerve | <anatomy, nerve> The portion of the optic nerve anterior to the lamina cribrosa of the sclera. Synonym: pars prelaminaris nervi optici. (05 Mar 2000) |
| principal optic axis | A line passing through the centre of the lens of a refracting system at right angles to its surface. (05 Mar 2000) |