| lens placodes | Paired ectodermal placode's that become invaginated to form the embryonic lens vesicles. Synonym: optic placodes. (05 Mar 2000) |
|---|---|
| lens, simple | <microscopy> A glass disk ground and polished with a spherical figure on one side and a plano, concave, or convex configuration on the other side. (05 Aug 1998) |
| lens stars | Congenital cataracts with opacities along the suture lines of the lens; may be anterior or posterior or both. (05 Mar 2000) |
| lens subluxation | Incomplete rupture of the zonule with the displaced lens remaining behind the pupil. In dislocation, or complete rupture, the lens is displaced forward into the anterior chamber or backward into the vitreous body. When congenital, this condition is known as ectopia lentis. (12 Dec 1998) |
| lens sutures | 9 to 12 faint lines on the anterior and posterior surfaces of the lens that radiate from the poles toward the equator; they mark the lines along which the ends of lens fibres abut. Synonym: lens stars, lens sutures. (05 Mar 2000) |
| lens vesicle | In the embryo, the ectodermal invagination that forms opposite the optic cup; it is the primordium of the lens of the eye. Synonym: lenticular vesicle. (05 Mar 2000) |
| lighthouse lens | <physics> A lens built up, progressively, in zones or steps, each zone with its own individual radius. Considerable spherical correction is attained, and the weight of the lens is greatly reduced. Fresnel lenses were originally designed for lighthouses but they are now attainable for small spotlights, automobile headlights, and similar uses. (05 Aug 1998) |
| accelerator fibres | Postganglionic sympathetic nerve fibre's originating in the superior, middle, and inferior cervical ganglia of the sympathetic trunk, conveying nervous impulses to the heart that increase the rapidity and force of the cardiac pulsations. Synonym: augmentor fibres. (05 Mar 2000) |
| adrenergic fibres | Nerve fibres liberating catecholamines at a synapse after an impulse. (12 Dec 1998) |
| afferent fibres | Those that convey impulses to a ganglion or to a nerve centre in the brain or spinal cord. (05 Mar 2000) |
| A fibres | Myelinated nerve fibre's in somatic nerves, measuring 1 to 22 um in diameter, conducting nerve impulses at a rate of 6 to 120 m/sec. (05 Mar 2000) |
| alpha fibres | Large somatic motor or proprioceptive nerve fibre's conducting impulses at rates near 100 m/sec. (05 Mar 2000) |
| anastomosing fibres | Anastomotic fibres, individual fibre's passing from one nerve trunk or muscle bundle to another. (05 Mar 2000) |
| arcuate fibres | Nervous or tendinous fibre's passing in the form of an arch from one part to another. See: arcuate fibres of cerebrum, external arcuate fibres, internal arcuate fibres. (05 Mar 2000) |
| arcuate fibres of cerebrum | Short association fibres that connect adjacent gyri in the cerebral cortex. Synonym: fibrae arcuatae cerebri. (05 Mar 2000) |