| ventral tegmental area | A region in the mesencephalon which is dorsomedial to the substantia nigra and ventral to the red nucleus. The mesocortical and mesolimbic dopaminergic systems originate here, including an important projection to the nucleus accumbens. Overactivity of the cells in this area has been suspected to contribute to the positive symptoms of schizophrenia. (12 Dec 1998) |
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| ventral tegmental decussation | See: tegmental decussations. (05 Mar 2000) |
| ventral thalamic peduncle | The massive system of fibre bundles emerging through the ventral, lateral, and anterior borders of the thalamus to join the internal capsule and parts of the corona radiata; it contains the fibres reciprocally connecting the ventral thalamic nuclei with the precentral and postcentral gyri of the cerebral cortex. Synonym: pedunculus thalami ventralis. (05 Mar 2000) |
| ventral tier thalamic nuclei | Collective term for nuclei in the ventral part of the lateral nuclear group, e.g., ventral anterior, lateral, posterolateral, and posteromedial nuclei and the medial and lateral geniculate bodies. The basoventral nuclear complex constitutes the caudal part of the ventral tier thalamic nuclei. (05 Mar 2000) |
| ventral white column | A narrow band of white substance bordering on the anterior median fissure of the spinal cord in front of the anterior gray commissure, and consisting of nerve fibres crossing over from one half of the spinal cord to the other. Synonym: commissura alba, anterior white commissure, commissura ventralis alba, ventral white column. (05 Mar 2000) |
| lateral cutaneous branches of ventral primary ramus of thoracic spinal nerves | Branches arising in approximately the anterior axillary line at the level of the second through sixth intercostal spaces. Synonym: rami mammarii laterales nervorum intercostalium, lateral cutaneous branches of intercostal nerves. (05 Mar 2000) |
| lateral ventral hernia | Abdominal hernia through the semilunar line. Synonym: lateral ventral hernia. (05 Mar 2000) |
| alimentary tract | The passage leading from the mouth to the anus through the pharynx, oesophagus, stomach, and intestine. Synonym: alimentary canal, alimentary tract, digestive tube, tubus digestorius. (05 Mar 2000) |
| alimentary tract smear | A group of cytologic specimens containing material from the mouth (oral smear), oesophagus and stomach (gastric smear), duodenum (paraduodenal smear), and colon, obtained by specialised lavage techniques; used principally for the diagnosis of cancer of those areas. (05 Mar 2000) |
| anterior corticospinal 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) |
| anterior spinocerebellar tract | A bundle of fibres originating in the base of the posterior horn and zona intermedia throughout lumbosacral segments of the spinal cord, crossing to the opposite side and ascending in a peripheral position in the ventral half of the lateral funiculus. In its ascent through the rhombencephalon, the tract curves sharply dorsalward along the rostral border of the trigeminal motor nucleus, entering the cerebellum in a caudal direction over the dorsal surface of the superior cerebellar peduncle, and terminating as mossy fibres in the granular layer of the cortex of the cerebellar vermis. The bundle conveys proprioceptive and exteroceptive information largely from the opposite lower extremity. Synonym: tractus spinocerebellaris anterior, Gowers' column, Gowers' tract, ventral spinocerebellar tract. (05 Mar 2000) |
| anterior spinothalamic tract | The more anterior or ventral part of the spinothalamic tract that is involved in tactile sensation. See: spinothalamic tract. Synonym: tractus spinothalamicus anterior, ventral spinothalamic tract. (05 Mar 2000) |
| Arnold's tract | A fibre group originating in the cerebral cortex of the temporal lobe, particularly the superior and middle temporal gyri, following the sublenticular limb of the internal capsule into the lateral margin of the crus cerebri in which it descends to its termination in the pontine nuclei or the ventral part of the pons. Synonym: tractus temporopontinus, Arnold's bundle, Arnold's tract. (05 Mar 2000) |
| association tract | See: association system. (05 Mar 2000) |
| auditory tract | A bundle of ascending fibres that originate from the cochlear and auditory relay nuclei of the rhombencephalon, enter the trapezoid body, a transverse fibre stratum in which about half their number decussate, and from here turn rostrally along the lateral side of the spinothalamic tract; in the midbrain, it arches dorsally and enters the inferior colliculus in which all of its fibres terminate; the auditory pathway is transsynaptically extended from here by the brachium of the inferior colliculus to the medial geniculate body of the thalamus, from which in turn the auditory radiation leads to the auditory cortex; intercalated in the trapezoid body and along the ascending trajectory of the lemniscus are several cell groups in which part of the fibres synapse. Synonym: lemniscus lateralis, acoustic lemniscus, auditory lemniscus, auditory tract, lateral fillet. (05 Mar 2000) |