| OG | obstetrics and gynecology; occlusogingival; oligodendrocyte; optic ganglion; orange green; orogastri... |
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| ON | occipitonuchal; office nurse; onlay; optic nerve; orthopedic nurse; osteonecrosis; osteonectin; over... |
| ONG | optic nerve glioma |
| OOA | outer optic anlage |
| OR | a logical binary relation that is true if any argument is true, and false otherwise; [o]estrogen rec... |
| anterior pyramidal 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) |
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| 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) |
| benign mesothelioma of genital tract | A small, circumscribed, benign tumour of the genital tract, composed of small glandlike spaces lined by flattened or cuboidal mesothelium-like cells. (12 Dec 1998) |
| biliary tract | <anatomy> The biliary tract refers to the bile ducts within the liver, the common bile duct (connecting the liver and gallbladder to the small intestine) and the cystic duct (short duct that connects the common bile duct to the gallbladder). Blockage in any location in the biliary tract can result in obstructive jaundice. (27 Sep 1997) |
| biliary tract surgical procedures | Any surgical procedure performed on the biliary tract. (12 Dec 1998) |
| Burdach's tract | 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) |
| gastrointestinal tract | <anatomy> The gastrointestinal tract starts from the oral cavity and proceeds to the oesophagus, stomach, duodenum, small intestine, large intestine, rectum and anus. (12 Jan 1998) |
| mamillothalamic tract | A compact, thick bundle of nerve fibres that passes dorsalward from the mamillary body on either side to terminate in the anterior nucleus of the thalamus. Synonym: fasciculus mamillothalamicus, fasciculus thalamomamillaris, mamillothalamic tract, Vicq d'Azyr's bundle. (05 Mar 2000) |
| ventral 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) |
| ventral 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) |
| Marchi's 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) |