| tractus tectospinalis | A bundle of thick, heavily myelinated fibres originating in the deep layers of the superior colliculus, crossing to the opposite side in the dorsal tegmental decussation, descending along the median plane, between the medial longitudinal fasciculus dorsally, the medial lemniscus ventrally, into the anterior funiculus of the spinal cord. The tract ends in the medial region of the anterior horn of the cervical spinal cord, and appears to be involved in head movements during visual and auditory tracking. Throughout its course in the brainstem it is accompanied by fibres of the tectobulbar tract. Synonym: tractus tectospinalis, Held's bundle, Loewenthal's bundle, Loewenthal's tract, Marchi's tract, predorsal bundle. (05 Mar 2000) |
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| tractus tegmentalis centralis | A large fibre bundle passing longitudinally through the central mesencephalic and pontine tegmentum, distinguished from adjacent longitudinal groups of fibre-fascicles of the reticular formation by a more compact composition. In transverse sections of the mesencephalon the bundle occupies a large triangular area lateral to the medial longitudinal fasciculus; farther caudally it expands ventralward and finally passes over the lateral side of the (inferior) olivary nucleus, becoming part of the latter's fibre capsule. The bundle contains fibres from the mesencephalic tegmentum and regions surrounding the central gray substance descending to the olivary nucleus; it also includes numerous fibres ascending from the medullary, pontine, and mesencephalic reticular formation to the thalamus and subthalamus region. Synonym: tractus tegmentalis centralis, central tegmental fasciculus, tractus centralis tegmenti. (05 Mar 2000) |
| tractus temporopontinus | 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) |
| tractus tuberoinfundibularis | A system of fine, unmyelinated fibres apparently originating from small-celled nuclei of the tuber cinereum, especially the arcuate nucleus, and terminating in the median eminence of the infundibulum, in contact with modified ependymal cells and the capillary tufts from which the hypothalamohypophysial portal veins originate. See: hypophysis, neurosecretion. Synonym: tractus tuberoinfundibularis. (05 Mar 2000) |
| tractus vestibulospinalis | A somatopically organised fibre bundle originating from the lateral vestibular nucleus (nucleus of Deiters) which descends uncrossed into the anterior funiculus of the spinal cord lateral to the anterior median fissure; the tractus extends throughout the length of the cord, distributing fibres at all levels to the medial part of the anterior horn. Excitatory impulses conveyed by the vestibulospinal tract increase extensor muscle tone. Synonym: tractus vestibulospinalis, deiterospinal tract. (05 Mar 2000) |
| acute anterior poliomyelitis | Inflammation of the anterior cornua of the spinal cord; an acute infectious disease caused by the poliomyelitis virus and marked by fever, pains, and gastroenteric disturbances, followed by a flaccid paralysis of one or more muscular groups, and later by atrophy. Synonym: acute atrophic paralysis, myogenic paralysis. (05 Mar 2000) |
| alpha cells of anterior lobe of hypophysis | Acidophil cell's that constitute about 35% of the cell's of the anterior lobe. There are two varieties: one that elaborates somatotropin, another that elaborates prolactin. (05 Mar 2000) |
| anterior | <anatomy> Toward the front or in front of. (27 Sep 1997) |
| anterior ampullar nerve | <anatomy, nerve> A branch of the utriculoampullar nerve that supplies the crista ampullaris of the anterior saemicircular duct. Synonym: nervus ampullaris anterior. (05 Mar 2000) |
| anterior antebrachial nerve | <anatomy, nerve> A branch of the median arising in elbow region, running on interosseous membrane, supplying the flexor pollicis longus, part of flexor digitorum profundus and the pronator quadratus muscles, as well as radiocarpal and intercarpal joints. Synonym: nervus interosseus anterior, ramus profundus nervi radialis, nervus antebrachii anterior, anterior antebrachial nerve, volar interosseous nerve. (05 Mar 2000) |
| anterior antebrachial region | The area between the radial and ulnar borders of the forearm anteriorly. Synonym: facies antebrachialis anterior, regio antebrachialis anterior, anterior antebrachial region, anterior surface of forearm, facies anterior antebrachii. (05 Mar 2000) |
| anterior aphasia | A type of aphasia in which there is a deficit in speech production or language output, often accompanied by a deficit in communicating by writing, signs, etc. The patient is aware of his impairment. Synonym: anterior aphasia, ataxic aphasia, Broca's aphasia, expressive aphasia, nonfluent aphasia. (05 Mar 2000) |
| anterior arch of atlas | An arch that connects the lateral masses of the atlas anteriorly and articulates with the anterior articular facet of the dens of the axis. Synonym: arcus anterior atlantis. (05 Mar 2000) |
| anterior asynclitism | Inclination of the foetal head in cases of flat pelvis, so that the biparietal diameter is oblique in relation to the plane of the pelvic brim, the anterior parietal bone presenting to the parturient canal. Synonym: anterior asynclitism. (05 Mar 2000) |
| anterior auricular | <anatomy, muscle> Origin, galea aponeurotica; insertion, cartilage of auricle; action, draws pinna of ear upward and forward; nerve supply, facial. Considered by some to be the anterior part of the temporoparietal muscle. Synonym: musculus auricularis anterior, musculus attrahens aurem, musculus attrahens auriculam, zygomaticoauricularis. (05 Mar 2000) |