| LAS | laboratory automation system; lateral amyotrophic sclerosis; laxative abuse syndrome; left anterior-... |
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| LASH | left anterior superior hemiblock |
| LSR | lanthanide shift reagent; lecithin/ sphingomyelin ratio; left superior rectus [muscle]; liver/spleen... |
| LSVC | left superior vena cava |
| MSO | management service organization; medial superior olive; medical staff organization |
| fasciculus | Origin: L. See Fascicle. 1. A little bundle; a fascicle. 2. A division of a book. Source: Websters Dictionary (01 Mar 1998) |
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| fasciculus anterior proprius | The ground bundle of the anterior column of the spinal cord. See: fasciculi proprii. Synonym: anterior ground bundle. Origin: L. Dim. Of fascis, bundle (05 Mar 2000) |
| fasciculus atrioventricularis | The bundle of modified cardiac muscle fibres that begins at the atrioventricular node as the trunk of the atrioventricular bundle and passes through the right atrioventricular fibrous ring to the membranous part of the interventricular septum where the trunk divides into two branches, the right crus of the atrioventricular bundle and the left crus of the atrioventricular bundle; the two crura ramify in the subendocardium of their respective ventricles. Synonym: fasciculus atrioventricularis, atrioventricular band, Gaskell's bridge, His' band, His' bundle, bundle of His, Keith's bundle, Kent's bundle, Kent-His bundle, ventriculonector. (05 Mar 2000) |
| fasciculus circumolivaris pyramidis | An anomalous bundle of nerve fibres on the anterior surface of the medulla oblongata that emerges from the pyramid and curves forward and dorsally over the lower pole of the olive; it is variously interpreted as an aberrant bundle of pontocerebellar fibres or corticopontine fibres. (05 Mar 2000) |
| fasciculus corticospinalis anterior | 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) |
| fasciculus corticospinalis lateralis | 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) |
| fasciculus cuneatus | The larger lateral subdivision of the posterior funiculus. Synonym: fasciculus cuneatus, Burdach's column, Burdach's fasciculus, Burdach's tract, cuneate funiculus, wedge-shaped fasciculus. (05 Mar 2000) |
| fasciculus dorsolateralis | A longitudinal bundle of thin, unmyelinated and poorly myelinated fibres capping the apex of the posterior horn of the spinal gray matter, composed of posterior root fibres and short association fibres that interconnect neighboring segments of the posterior horn. Synonym: fasciculus dorsolateralis, tractus dorsolateralis, dorsolateral tract, fasciculus marginalis, Lissauer's bundle, Lissauer's column, Lissauer's fasciculus, Lissauer's marginal zone, Lissauer's tract, marginal fasciculus, Spitzka's marginal tract, Spitzka's marginal zone, Waldeyer's tract, Waldeyer's zonal layer. (05 Mar 2000) |
| fasciculus gracilis | The smaller medial subdivision of the posterior funiculus. Synonym: fasciculus gracilis. (05 Mar 2000) |
| fasciculus lateralis plexus brachialis | In the brachial plexus, the bundle of nerve fibres formed by the anterior divisions of the superior and middle trunks which is located lateral to the axillary artery. This cord gives off the lateral pectoral nerve and terminates by dividing into the musculocutaneous nerve and the lateral root of the median nerve. Synonym: fasciculus lateralis plexus brachialis. (05 Mar 2000) |
| fasciculus lateralis proprius | Flechsig's fasciculi or ground bundles (f. Anterior proprius and fasciculus lateralis proprius or lateral ground bundle); intersegmental fasciculi; ascending and descending association fibre systems of the spinal cord which lie deep in the anterior, lateral, and posterior funiculi adjacent to the gray matter. Synonym: ground bundles, intersegmental fasciculi, proper fasciculi. (05 Mar 2000) |
| fasciculus lenticularis | The pallidal efferent fibres that cross the internal capsule and are insinuated between the subthalamic nucleus and zona incerta; they join in the formation of the thalamic fasciculus. See: lenticular loop. Synonym: fasciculus lenticularis. (05 Mar 2000) |
| fasciculus longitudinalis dorsalis | A bundle of thin, poorly myelinated nerve fibres reciprocally connecting the periventricular zone of the hypothalamus with ventral parts of the central gray substance of the midbrain. Synonym: fasciculus longitudinalis dorsalis, Schutz' bundle, tract of Schutz. (05 Mar 2000) |
| fasciculus longitudinalis inferior | A well marked bundle of long association fibres running the whole length of the occipital and temporal lobes of the cerebrum, in part parallel with the inferior horn of the lateral ventricle. Synonym: fasciculus longitudinalis inferior. (05 Mar 2000) |
| fasciculus longitudinalis medialis | A longitudinal bundle of fibres extending from the upper border of the mesencephalon into the cervical segments of the spinal cord, located close to the midline and ventral to the central gray matter; it is composed largely of fibres from the vestibular nuclei ascending to the motor neurons innervating the external eye muscles (abducens, trochlear, and oculomotor nuclei), and descending to spinal cord segments innervating the musculature of the neck. Synonym: fasciculus longitudinalis medialis, Collier's tract, medial longitudinal bundle, posterior longitudinal bundle. (05 Mar 2000) |