| neural segment | Alternate swellings and constrictions seen along the neuraxis at early stages of neural tube development, thought to be evidence of intrinsic segmentation in the CNS. Neuromeres or segments in the hindbrain region are called rhombomeres and have been shown to be lineage restriction units, each constructing a defined piece of hindbrain. (18 Nov 1997) |
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| neural spine | The middle point of the neural arch of the typical vertebra, represented by the spinous process. (05 Mar 2000) |
| neural tube | <embryology> The progenitor of the central nervous system. See: neural plate, neurulation. (18 Nov 1997) |
| neural tube defect | <neurology, paediatrics> Abnormal development during embryonic life of the neural tube producing congenital malformations of the nervous system due to closure failure of the neural tube. The structure gives rise to the central nervous system (the brain and spinal cord), and failure to close results in anencephaly (absence of the cranial vault and absence of most or all of the cerebral hemispheres of the brain) and spina bifida or meningomyelocele (open spina with exposure and protusion of the spinal cord). The risk of neuroal tube defects can be decreased by the mother taking folic acid during pregnancy. (04 Jul 1999) |
| dorsal plate of neural tube | The thin layer of the embryonic neural tube connecting the alar plate's dorsally. Synonym: dorsal plate of neural tube. (05 Mar 2000) |
| dorsolateral plate of neural tube | The dorsal division of the lateral walls of the neural tube in the embryo; it gives rise to neurons relaying afferent impulses to higher centres; in the adult such neurons compose the sensory nuclei of the spinal cord and brainstem. Synonym: lamina alaris, alar plate of neural tube, dorsolateral plate of neural tube, lamina dorsalis, wing plate. (05 Mar 2000) |
| oesophageal hiatus | The opening in the right crus of the diaphragm, between the central tendon and the hiatus aorticus, through which pass the oesophagus and the two vagus nerves. Synonym: hiatus oesophageus, oesophageal opening. (05 Mar 2000) |
| fallopian hiatus | The opening on the anterior aspect of the petrous part of the temporal bone which leads to the facial canal and gives passage to the greater petrosal nerve. Synonym: hiatus canalis nervi petrosi majoris, fallopian hiatus, Ferrein's foramen, hiatus canalis facialis, hiatus of canal for greater petrosal nerve. (05 Mar 2000) |