| neuroectodermal junction | The margin of the embryonic neural plate separating it from the embryonic ectoderm; cells from this region form the neural crest. Synonym: neurosomatic junction. (05 Mar 2000) |
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| melanotic neuroectodermal tumour of infancy | A benign neoplasm of neuroectodermal origin that most often involves the anterior maxilla of infants in the first year of life. It presents clinically as a rapidly growing blue-black lesion producing a destructive radiolucency; histologically, it is characterised by small round undifferentiated tumour cells interspersed with larger polyhedral melanin-producing cells arranged in an alveolar configuration. Synonym: melanoameloblastoma, pigmented ameloblastoma, pigmented epulis, progonoma of jaw, retinal anlage tumour. (05 Mar 2000) |
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| primitive neuroectodermal tumour | A designation used to refer to a group of morphologically similar embryonal neoplasms that arise in intracranial and peripheral sites of the nervous system and which may show various degrees of cellular differentiation; includes medulloblastoma, pineoblastoma, etc. (05 Mar 2000) |
| primitive neuroectodermal tumours | A type of brain tumour. Prenatal diagnosis: diagnosis before birth. Methods for prenatal diagnosis include ultrasound (of the uterus, placenta and developing foetus), chorionic villus sampling to obtain tissue for chromosome or biochemical analysis, amniocentesis to obtain amniotic fluid for the analysis of chromosmes, enzymes, DNA, etc. A growing number of birth defects and diseases are now amenable to prenatal diagnosis. Also called antenatal diagnosis. (12 Dec 1998) |
| neuroectodermal | Relating to the neuroectoderm. (05 Mar 2000) |
| neuroectodermal tumour, melanotic | A benign, rapidly growing, deeply pigmented tumour of the jaw and occasionally of other sites, consisting of an infiltrating mass of cells arranged in an alveolar pattern, and occurring almost exclusively in infants. Its source of origin is in dispute, the various theories giving rise to its several names. (12 Dec 1998) |
| neuroectodermal tumour, peripheral | A heterogeneous group of malignant neoplasms arising in either supportive structures or neuronal tissue. They occur in adolescents and young adults. This tumour shares a number of characteristics with ewing's sarcoma: it is highly cellular and consists of a monotonous pattern of primitive-appearing round cells. The chest wall is the most common site but the trunk, abdomen, and pelvis are other primary sites. (12 Dec 1998) |
| neuroectodermal tumour, primitive | A malignant brain tumour sharing common features and biologic properties with medulloblastoma. Some pathologists and clinicians use the terms interchangeably: they both can disseminate throughout the nervous system and, in some cases, systemically. most lesions arise from the posterior fossa in children under five years of age. The tumour often produces hydrocephalus and symptoms of increased intracranial pressure. Papilledema is often present. (12 Dec 1998) |
| neuroectodermal tumours | Malignant neoplasms arising in the neuroectoderm, the portion of the ectoderm of the early embryo that gives rise to the central and peripheral nervous systems, including some glial cells. (12 Dec 1998) |
| adhering junction | <cell biology> A type of junction between cells forming tissues that are subjected to stretching and pulling, such as the skin. This type of junction provides very tight contact between adjacent cells and allows the cells to fuction as a unit. Belt desmosomes are attachment sites that circle the cell, and spot desmosomes are small points of attachment across the cells surface. (15 Jan 1998) |
| amelodental junction | Amelodentinal junction, rarely used terms for dentinoenamel junction. (05 Mar 2000) |
| amnioembryonic junction | The line of amniotic attachment to the periphery of the embryonic disk. (05 Mar 2000) |
| anorectal junction | Transition from rectum to anal canal; corresponds to the perineal flexure, or the level at which the gut perforates the pelvic diaphragm; here the rectal ampulla narrows abruptly into a narrow slip. (05 Mar 2000) |
| anterior junction line | Radiographic projection of the mediastinal tissue septum between the upper lobes behind the sternum. (05 Mar 2000) |
| A-V junction | Imprecisely defined zone surrounding and including the A-V node and the adjacent atrial and ventricular myocardium. (05 Mar 2000) |
| cardioesophageal junction | The abrupt transition from oesophageal mucosa to that of the cardiac portion of stomach, demarcated internally in the living by the z-line, and approximated externally by the cardiac notch. (05 Mar 2000) |