| intestinal tract | <anatomy> This includes the coarse of the small and large intestines and includes approximately 27 feet of bowel. (27 Sep 1997) |
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| occipitocollicular tract | The system of nerve fibres by which the occipital cortex projects to the superior colliculus. Synonym: occipitocollicular tract. (05 Mar 2000) |
| occipitopontine tract | 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) |
| occipitotectal tract | The system of nerve fibres by which the occipital cortex projects to the superior colliculus. Synonym: occipitocollicular tract. (05 Mar 2000) |
| olfactory tract | 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) |
| olivocerebellar tract | A large group of loosely arranged fibre fascicles emerging from the hilus of the olivary nucleus, crossing to the opposite side of the medulla oblongata through the stratum interolivare lemnisci and the contralateral olive, and joining the restiform body, the larger part of the contralateral inferior cerebellar peduncle; its fibres terminate in all parts of the cerebellar cortex as climbing fibres. Synonym: tractus olivocerebellaris. (05 Mar 2000) |
| olivocochlear tract | See: olivocochlear bundle. (05 Mar 2000) |
| olivospinal tract | A slender bundle of nerve fibres in the peripheral zone of the lateral funiculus of the spinal cord, composed of spino-olivary fibres more likely than olivospinal fibres. Synonym: Helweg's bundle. (05 Mar 2000) |
| optic tract | 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) |
| tectobulbar tract | Fibres originating in the deep layers of the superior colliculus and accompanying the tectospinal tract but, unlike the latter, terminating in medial regions of the pontine and medullary tegmentum. Synonym: tractus tectobulbaris. (05 Mar 2000) |
| tectopontine tract | A fibre bundle arising in the superior colliculus, passing caudoventrally on the same side along the medial side of the lateral lemniscus, issuing fibres terminating in the lateral zone of the mesencephalic tegmentum, and ending in the lateral part of the gray matter of the ventral part of the pons. Synonym: tract of Munzer and Wiener, tractus tectopontinus. (05 Mar 2000) |
| tectospinal tract | 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) |
| temporofrontal tract | A band of long association fibres reciprocally connecting the frontal and temporal lobes of the cerebrum, running caudally through the white matter of the frontal lobe, sharply curving ventrally under the stem of the sylvian fissure, and then fanning out to the cortex of the anterior half of the superior and middle temporal gyri. Synonym: fasciculus uncinatus, arcuate fasciculus, frontotemporal tract, hooked fasciculus, temporofrontal tract. (05 Mar 2000) |
| temporopontine 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) |
| tract | <anatomy> A region, principally one of some length, specifically a collection or bundle of nerve fibres having the same origin, function and termination (tractus) or a number of organs, arranged in series, subserving a common function. Origin: L. Tractus (18 Nov 1997) |