| optic tectum | <anatomy> A region of the midbrain in which input from the optic nerve is processed. Because the retinally derived neurons of the optic nerve map onto the optic tectum in a defined way, the question of how this specificity is determined has been a long standing problem in cell biology. Although there is some evidence for adhesion gradients and for some adhesion specificity, the problem is unresolved. (11 Jan 1998) |
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| optic tract | The continuation of the optic nerve fibres beyond (behind) the latter's hemidecussation in the optic chiasm; each of the two symmetrical optic tracts is composed of fibres originating from the temporal half of the retina of the ipsilateral eye and a nearly equal number of fibres from the nasal half of the contralateral retina; it forms a compact, somewhat flattened fibre band passing caudolaterally alongside the base of the hypothalamus and over the basal surface of the crus cerebri; most of its fibres terminate in the lateral geniculate body; a smaller number of fibres enter the brachium of the superior colliculus, to terminate in the superior colliculus and the pretectal region. Synonym: tractus opticus. (05 Mar 2000) |
| optic vesicle | In the embryo, one of the paired evaginations from the ventrolateral walls of the forebrain from which the sensory and pigment layers of the retina develop. Synonym: vesicula ophthalmica, ocular vesicle, optic vesicle. (05 Mar 2000) |
| orbital part of optic nerve | <anatomy, nerve> The part of the optic nerve between the eye and the optic canal. Synonym: pars orbitalis nervi optici. (05 Mar 2000) |
| excavation of optic disc | The normally occurring depression or pit in the centre of the optic disc. Synonym: excavatio disci, depression of optic disk, excavatio papillae, physiologic cup, physiologic excavation. (05 Mar 2000) |
| external sheath of optic nerve | <anatomy, nerve> The outer sheath around the optic nerve, continuous with the dura mater. Synonym: vagina externa nervi optici, dural sheath of optic nerve. (05 Mar 2000) |
| lateral root of optic tract | The larger division of the posterior end of the optic tract that terminates in the lateral geniculate body. Synonym: radix lateralis tractus optici. (05 Mar 2000) |
| lenticulo-optic | Relating to the lentiform nucleus and the optic tract; specifically refers to branches of the middle cerebral artery considered to supply these structures. (05 Mar 2000) |
| acute reflex bone atrophy | Atrophy of bones, commonly of the carpal or tarsal bones, following a slight injury such as a sprain. See: causalgia, reflex sympathetic dystrophy. Synonym: acute reflex bone atrophy, posttraumatic osteoporosis, Sudeck's syndrome. Origin: L. English sweat (05 Mar 2000) |
| acute yellow atrophy of the liver | A lesion in which there is extensive and rapid death of parenchymal cells of the liver, sometimes with fatty degeneration of the size of the organ; the necrosis may result from fulminant viral infection or chemical poisoning; associated with jaundice. Synonym: acute parenchymatous hepatitis, Rokitansky's disease. (05 Mar 2000) |
| alveolar atrophy | Diminution in size of the supportive tissues of the teeth due to lack of function, reduced blood supply, or unknown causes. (05 Mar 2000) |
| arthritic atrophy | Atrophy of muscles rendered inactive by a chronically inflamed or fixed joint. (05 Mar 2000) |
| atrophy | <pathology> A wasting away, a diminution in the size of a cell, tissue, organ or part. Origin: L., Gr. Atrophia (16 Dec 1997) |
| back-pressure renal atrophy | <radiology> Caliectasis without obstruction, due to repeated episodes of obstruction, gradual loss of renal pyramids (12 Dec 1998) |
| blue atrophy | Depressed blue atrophic scars due to injections in the skin of impure substances, as seen in narcotics addicts. (05 Mar 2000) |