| optic decussation | <anatomy> The anatomic point of crossing or decussation of the optic nerve fibres. most of the nerve fibres cross to the opposite side. (27 Sep 1997) |
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| tectospinal decussation | See: tegmental decussations. (05 Mar 2000) |
| Forel's decussation | The dorsal tegmental decussation (fountain or Meynert's decussation, decussatio fontinalis) of the left and right tectospinal and tectobulbar tracts, the ventral tegmental decussation (rubrospinal or Forel's decussation) of the left and right rubrospinal and rubrobulbar tracts; both are located in the mesencephalon. Synonym: decussationes tegmenti. (05 Mar 2000) |
| fountain decussation | See: tegmental decussations. (05 Mar 2000) |
| anterior pyramidal fasciculus | Uncrossed fibres forming a small bundle in the pyramidal tract. See: pyramidal tract. Synonym: tractus corticospinalis anterior, tractus pyramidalis anterior, anterior corticospinal tract, anterior pyramidal fasciculus, direct pyramidal tract, fasciculus corticospinalis anterior, fasciculus pyramidalis anterior, Turck's bundle, Turck's column, Turck's tract. (05 Mar 2000) |
| anterior pyramidal tract | Uncrossed fibres forming a small bundle in the pyramidal tract. See: pyramidal tract. Synonym: tractus corticospinalis anterior, tractus pyramidalis anterior, anterior corticospinal tract, anterior pyramidal fasciculus, direct pyramidal tract, fasciculus corticospinalis anterior, fasciculus pyramidalis anterior, Turck's bundle, Turck's column, Turck's tract. (05 Mar 2000) |
| crossed pyramidal tract | Those fibres of the pyramidal tract that cross to the opposite side in the pyramidal decussation and descend in the dorsal half of the lateral funiculus of the spinal cord; they are distributed throughout the length of the spinal cord to interneurons of the zona intermedia of the spinal gray matter. See: pyramidal tract. Synonym: tractus corticospinalis lateralis, tractus pyramidalis lateralis, crossed pyramidal tract, fasciculus corticospinalis lateralis, fasciculus pyramidalis lateralis, lateral corticospinal tract, lateral pyramidal fasciculus. (05 Mar 2000) |
| pyramidal | 1. Of or pertaining to a pyramid; in the form of a a pyramid; pyramidical; as, pyramidal cleavage. "The mystic obelisks stand up Triangular, pyramidal." (Mrs. Browning) 2. <chemistry> Same as Tetragonal. <mathematics> Pyramidal numbers, certain series of figurate numbers expressing the number of balls or points that may be arranged in the form of pyramids. Thus 1, 4, 10, 20, 35, etc, are trangular pyramidal numbers; and 1, 5, 14, 30, 55, etc, are square pyramidal numbers. Origin: Cf. F. Pyramidal. <anatomy> One of the carpal bones. See Cuneiform, 2 . Source: Websters Dictionary (01 Mar 1998) |
| pyramidal auricular muscle | <anatomy> An occasional prolongation of the fibres of the tragicus to the spina helicis. Synonym: musculus pyramidalis auriculae, Jung's muscle, pyramidal muscle of auricle. (05 Mar 2000) |
| pyramidal bone | A bone on the medial (ulnar) side of the proximal row of the carpus, articulating with the lunate, pisiform, and hamate. Synonym: os triquetrum, cubital bone, os pyramidale, os triangulare, pyramidal bone, pyramidale, three-cornered bone, triquetrum. (05 Mar 2000) |
| pyramidal cataract | A cone-shaped, anterior polar cataract. (05 Mar 2000) |
| pyramidal cell | <anatomy, neurology> Commonest nerve cells of the cerebral cortex. (18 Nov 1997) |
| pyramidal cell layer | Layer 3 of the cortex cerebri. Synonym: Meynert's layer. (05 Mar 2000) |
| pyramidal cells | Projection neurons in the cerebral cortex and the hippocampus. Pyramidal cells have a pyramid-shaped soma with the apex and an apical dendrite pointed toward the pial surface and other dendrites and an axon emerging from the base. The axons may have local collaterals but also project outside their cortical region. (12 Dec 1998) |
| pyramidal disease | A condition of the horse's foot in which there is exostosis of the extensor process of the third phalanx, with swelling and chronic inflammation at the coronary band on the anterior surface of the foot. Synonym: pyramidal disease. (05 Mar 2000) |