| AICA | anterior inferior cerebellar artery; anterior inferior communicating artery |
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| ALH | angiolymphoid hyperplasia; anterior lobe hormone; anterior lobe of hypophysis |
| APL | abductor pollicis longus; accelerated painless labor; acute promyelocytic leukemia; animal placenta ... |
| CA | anterior commissure [Lat. commissura anterior]; calcium antagonist; California [rabbit]; cancer; Can... |
| LADA | laboratory animal dander allergy; left acromio-dorso-anterior [position]; left anterior descending a... |
| tractus corticobulbaris | <physiology> Collective term for those fibres (corticonuclear fibres) which separate from the corticospinal tract in the course of the latter's descent through the pons and medulla oblongata. Fibres of this tract innervate the motor nuclei of the trigeminal, facial, and hypoglossal nerves (perhaps also the nucleus ambiguus), directly and by way of interneurons in the lateral part of the rhombencephalic tegmentum. No direct supranuclear cortical innervation of the motor nuclei innervating the external eye muscles (oculomotor, trochlear, abducens) has been identified. Fibres of the corticobulbar tract also project into the formatio reticularis (i.e., corticoreticular fibres) and terminate upon sensory relay nuclei (e.g., gracile and cuneate nuclei, nucleus spinalis trigeminalis and nucleus solitarius). Synonym: tractus corticobulbaris. (05 Mar 2000) |
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| tractus corticopontini | <anatomy, physiology> Collective term for the multitude of fibres which, originating in all of the major subdivisions of the cerebral cortex, descend in the internal capsule and crus cerebri to terminate in the nuclei of the ventral part of the pons. Individual components of this massive fibre system are indicated, according to their origin in the cerebral cortex, as the frontopontine tract, parietopontine tract, occipitopontine tract, and temporopontine tract. Synonym: tractus corticopontini. (05 Mar 2000) |
| tractus corticospinalis | A massive bundle of fibres originating from pyramidal cells of various sizes in the fifth layer of the precentral motor (area 4), the premotor area (area 6), and to a lesser extent from the postcentral gyrus. Cells of origin in area 4 include the gigantopyramidal cells of Betz. Fibres from these cortical regions descend through the internal capsule, the middle third of the crus cerebri, and the ventral part of the pons to emerge on the ventral surface of the medulla oblongata as the pyramis. Continuing caudally, most of the fibres cross to the opposite side in the pyramidal decussation and descend in the dorsal half of the lateral funiculus of the spinal cord as the lateral pyramidal tract, which distributes its fibres throughout the length of the spinal cord to interneurons of the zona intermedia of the spinal gray matter. In the (extremity-related) spinal cord enlargements, fibres also pass directly to motoneuronal groups that innervate distal extremity muscles subserving particular hand-and-finger or foot-and-toe movements. The uncrossed fibres form a small bundle, the anterior pyramidal tract, which descends in the anterior funiculus of the spinal cord and terminates in synaptic contact with interneurons in the medial half of the anterior horn on both sides of the spinal cord. Interruption of the pyramidal tract at or below its cortical origin causes impairment of movement in the opposite body-half, especially severe in the arm and leg; characterised by muscular weakness, spasticity and hyperreflexia, and a loss of discrete finger and hand movements. Babinski's sign is associated with this condition of hemiplegia. Synonym: tractus corticospinalis, tractus pyramidalis, corticospinal tract. (05 Mar 2000) |
| tractus 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) |
| tractus descendens nervi trigemini | <anatomy, nerve> A compact fibre bundle, comma-shaped on transverse section, composed of primary sensory fibres of the portio major of the trigeminal nerve, descending from the level of the entrance of the trigeminus in the upper pons down through the dorsolateral region of the rhombencephalic tegmentum along the lateral side of the descending or spinal nucleus of the trigeminus, emerging on the dorsolateral surface of the lower medulla oblongata as the tuberculum cinereum, and continuing as far as the second cervical segment of the spinal cord. Its fibres are distributed to the descending or spinal nucleus of the trigeminus. Synonym: tractus spinalis nervi trigemini, descending tract of trigeminal nerve, tractus descendens nervi trigemini. (05 Mar 2000) |
| tractus 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) |
| tractus fastigiobulbaris | A fibre bundle originating in the fastigial nucleus (nucleus tecti) of both sides, passing out of the cerebellum in the inferior cerebellar peduncle (corpus restiforme), and distributing its fibres to the vestibular nuclei and other cell groups in the medulla oblongata. Prominent crossed fibres loop over the dorsal surface of the superior cerebellar peduncle before turning ventrally, forming the uncinate bundle of Russell. Synonym: tractus fastigiobulbaris. (05 Mar 2000) |
| tractus frontopontinus | A large group of fibres arising from the frontal lobe of the cerebral hemisphere, especially the precentral gyrus, descending in the capsula interna, farther caudally composing the medial part of the crus cerebri in which they extend caudalward to end in the gray matter (pontine nuclei) of the ventral part of the pons. Synonym: tractus frontopontinus. (05 Mar 2000) |
| tractus habenulopeduncularis | tractus habenulopeduncularis |
| tractus iliotibialis | A fibrous reinforcement of the fascia lata on the lateral surface of the thigh, extending from the crest of the ilium to the lateral condyle of the tibia. Synonym: tractus iliotibialis, iliotibial band, Maissiat's band. (05 Mar 2000) |
| tractus mesencephalicus nervi trigemini | <anatomy, nerve> Located alongside the central substance of the midbrain and composed of primary sensory fibres, the cells of origin of which compose the mesencephalic nucleus of the trigeminus. Synonym: tractus mesencephalicus nervi trigemini. (05 Mar 2000) |
| tractus occipitopontinus | A group of fibres originating in the occipital lobe of the cerebral hemisphere and descending in the internal capsule and lateral part of the crus cerebri to the pontine nuclei or ventral part of the pons. Synonym: tractus occipitopontinus. (05 Mar 2000) |
| tractus olfactorius | A nervelike, white band composed primarily of nerve fibres originating from the mitral cells and tufted cells of the olfactory bulb but also containing the scattered cells of the anterior olfactory nucleus. The tract is closely applied to the ventral surface of the frontal lobe, and attaches itself to the base of the cerebral hemisphere at the olfactory trigone, beyond which it extends in the form of the olfactory striae which distribute their fibres to the olfactory tubercle and, in largest number, to the olfactory cortex on and around the uncus of the parahippocampal gyrus. See: olfactory nerves. Synonym: tractus olfactorius, olfactory peduncle. (05 Mar 2000) |
| tractus olivocerebellaris | Synonym: olivocerebellar tract. (05 Mar 2000) |
| tractus opticus | The continuation of the optic nerve fibres beyond (behind) the latter's hemidecussation in the optic chiasm; each of the two symmetrical optic tracts is composed of fibres originating from the temporal half of the retina of the ipsilateral eye and a nearly equal number of fibres from the nasal half of the contralateral retina; it forms a compact, somewhat flattened fibre band passing caudolaterally alongside the base of the hypothalamus and over the basal surface of the crus cerebri; most of its fibres terminate in the lateral geniculate body; a smaller number of fibres enter the brachium of the superior colliculus, to terminate in the superior colliculus and the pretectal region. Synonym: tractus opticus. (05 Mar 2000) |