| herniated nucleus pulposus | <orthopaedics> A herniated intervertebral disk (nucleus pulposus) is one which has become displaced (prolapsed) from its normal position in between the vertebral bodies of the spine. Herniated disks often impinge on nearby nerve structures resulting in pain and neurologic symptoms. A clinical situation where the radicular nerve (nerve root) is compressed by the prolapsed disk is referred to as a radiculopathy. This problem tends to occur most commonly in the cervical and lumbar spine. (27 Sep 1997) |
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| herniation of nucleus pulposus | <radiology> Focal protrusion of disc material secondary to rupture of annulus fibrosus confined within the posterior longitudinal ligament location: L4/5 (35%); L5/S1 (27%); L3/4 (19%); L2/3 (14%); L1/2 (5%); thoracic spine affected in 3:1000 disc operations, posterolateral (49%): weakest point (posterior longitudinal ligament tightly adherent to posterior margin of disc), posterocentral (8%), lateral/foraminal (less than10%), intraosseous/vertical (14%): Schmorl node, extraforaminal/anterior (29%): commonly overlooked, bilateral: on both sided of the posterior ligament findings: disc (low T1) displaces posterior ligament/epidural fat (high T1), enlarged (edematous) nerve root: trumpet sign, see: degenerative disc disease extradural mass (12 Dec 1998) |
| Schwalbe's nucleus | One of a group of four main nuclei that includes: the lateral vestibular nucleus (Deiters' nucleus), medial vestibular nucleus (Schwalbe's nucleus), superior vestibular nucleus (Bechterew's nucleus), and inferior vestibular nucleus, located in the lateral region of the hindbrain beneath the floor of the rhomboid fossa. They receive primary fibres of the vestibular nerve, are reciprocally connected with the flocculonodular lobe of the cerebellum, and project by way of the medial longitudinal fasciculus to the abducens, trochlear, and oculomotor nuclei and to the ventral horn of the spinal cord. The lateral vestibular nucleus projects to the ipsilateral ventral horn of the spinal cord by the vestibulospinal tract. Synonym: nucleus vestibularis. (05 Mar 2000) |
| hilum of dentate nucleus | The mouth of the flasklike dentate nucleus of the cerebellum, directed inward, and giving exit to many of the fibres which compose the superior cerebellar peduncle or brachium conjunctivum. Synonym: hilum nuclei dentati. (05 Mar 2000) |
| hilum of olivary nucleus | The medially oriented opening in the folded cell layer composing the inferior olivary nucleus through which the efferent fibres of the nucleus make their exit. Synonym: hilum nuclei olivaris. (05 Mar 2000) |
| segmentation nucleus | The compound nucleus in the impregnated ovum, formed by conjugation of the nuclei of the ovum and spermatozoon (female and male pronuclei), the zygote nucleus after it commences the first cleavage division. (05 Mar 2000) |
| pulvinar nucleus | The large caudal portion of the lateral thalamic nuclear group; may be divided into oral, inferior, medial and lateral parts based on cytoarchitecture and connections; functionally related to the visual system. (05 Mar 2000) |
| semilunar nucleus of Flechsig | The small ventral region of the ventral posteromedial nucleus of thalamus in which the fibres of the gustatory lemniscus and secondary trigeminal tracts terminate; it projects to the lower part of the postcentral gyrus of the cerebral cortex. Synonym: arcuate nucleus, nucleus arcuatus thalami, nucleus arcuatus, semilunar nucleus of Flechsig, thalamic gustatory nucleus. (05 Mar 2000) |
| pyrrole nucleus | Of porphyrins, a cyclic tetrapyrrole; four pyrrole groups joined into a ring structure by way of -CH== (methylidyne) bridges between the a position of one pyrrole and the a' position of another pyrrole, the fourth pyrrole being joined to the first. See: porphin, porphyrin. (05 Mar 2000) |
| shadow nucleus | A nucleus that has lost its pigment and staining properties. (05 Mar 2000) |
| hypoglossal nucleus | The motor nucleus innervating the intrinsic and four of the five extrinsic muscles of the tongue; it is located in the medulla oblongata near the midline, immediately beneath the floor of the inferior recess of the rhomboid fossa. Synonym: nucleus nervi hypoglossi, nucleus of hypoglossal nerve. (05 Mar 2000) |
| solitary nucleus | Gray matter located in the dorsomedial part of the medulla oblongata associated with the solitary tract. The solitary nucleus receives inputs from most organ systems including the terminations of the facial, glossopharyngeal, and vagus nerves. It is a major coordinator of autonomic nervous system regulation of cardiovascular, respiratory, gustatory, gastrointestinal, and chemoreceptive aspects of homeostasis. The solitary nucleus is also notable for the large number of neurotransmitters which are found therein. (12 Dec 1998) |
| somatic nucleus | The larger nucleus (or sometimes nuclei) in ciliate protozoans. Derived from the micronucleus by a process of DNA polytenisation. The DNA in the macronucleus is actively transcribed. The macronucleus degenerates before conjugation. (18 Nov 1997) |
| sperm nucleus | The head of the spermatozoon, which becomes spheroidal, after entering the ovum. See: pronucleus. (05 Mar 2000) |
| spherical nucleus | Spinal nucleus of accessory nerve, a slender column of motor neurons extending longitudinally through the central part of the ventral horn of the upper five segments of the spinal cord, giving origin to the spinal part of the accessory nerve. Synonym: nucleus spinalis nervi accessorii, globosus nucleus. (05 Mar 2000) |