| rhombencephalic isthmus | A constriction in the embryonic neural tube delineating the mesencephalon from the rhombencephalon, the anterior portion of the rhombencephalon connecting with the mesencephalon. Synonym: isthmus rhombencephali, isthmus of His. (05 Mar 2000) |
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| Guyon's isthmus | An elongated constriction at the junction of the body and cervix of the uterus. Synonym: isthmus uteri, Guyon's isthmus, orificium internum uteri, os uteri internum, ostium uteri internum. (05 Mar 2000) |
| pharyngeal isthmus | Communicating space between nasopharynx and oropharynx, sealed off by elevation of the soft palate and contraction of portions of the superior pharyngeal constrictor (palatopharyngal sphincter) during swallowing. (05 Mar 2000) |
| sphincter of the pharyngeal isthmus | A constant band of the superior pharyngeal constrictor muscle which sweeps posteriorly from the anterolateral part of the superior surface of the palatine aponeurosis. It creates a visible ridge when the superior constrictor is contracted, meeting the elevated soft palate to seal off the pharyngeal isthmus during swallowing. Synonym: pharyngeal ridge, sphincter of the pharyngeal isthmus, velopharyngeal sphincter. (05 Mar 2000) |
| isthmus | Origin: L. Isthmus, Gr. 'isqmos a neck, a neck of land between two seas, an isthmus, especially the Isthmus of Corinth; prob. From the root of 'ienai to go; cf. Icel. Eith isthmus. See Issue. <geography> A neck or narrow slip of land by which two continents are connected, or by which a peninsula is united to the mainland; as, the Isthmus of Panama; the Isthmus of Suez, etc. Isthmus of the fauces. <anatomy> See Fauces. Source: Websters Dictionary (01 Mar 1998) |
| isthmus aortae | A slight constriction of the aorta immediately distal to the left subclavian artery at the point of attachment of the ductus arteriosus. Synonym: isthmus aortae. (05 Mar 2000) |
| isthmus cartilaginis auris | A narrow bridge connecting the cartilage of the external acoustic meatus and the lamina of the tragus with the main portion of the cartilage of the auricle. Synonym: isthmus cartilaginis auris. (05 Mar 2000) |
| isthmus faucium | The constricted and short space which establishes the connection between the cavity of the mouth and the oro-pharynx, bounded anteriorly by the palatoglossal folds and posteriorly by the palatopharyngeal folds; the lateral well is the tonsillar fossa. Synonym: isthmus faucium. (05 Mar 2000) |
| isthmus glandulae thyroideae | The central part of the thyroid gland joining the two lateral lobes. Synonym: isthmus glandulae thyroideae. (05 Mar 2000) |
| isthmus gyri cinguli | The narrowing of the cingulate gyrus, at its transition with the hippocampal gyrus behind and below the splenium of the corpus callosum, caused by the anterior extension of the conjoined parieto-occipital and calcarine sulci. Synonym: isthmus gyri cinguli, isthmus of gyrus fornicatus, isthmus of limbic lobe. (05 Mar 2000) |
| isthmus meatus acustici externi | The narrowest portion of this canal in the bony part near its deep termination. Synonym: isthmus meatus acustici externi. (05 Mar 2000) |
| isthmus of aorta | A slight constriction of the aorta immediately distal to the left subclavian artery at the point of attachment of the ductus arteriosus. Synonym: isthmus aortae. (05 Mar 2000) |
| isthmus of auditory tube | The narrowest portion of the auditory tube at the junction of the cartilaginous and bony portions. Synonym: isthmus tubae auditivae, isthmus of eustachian tube. (05 Mar 2000) |
| isthmus of cartilage of ear | A narrow bridge connecting the cartilage of the external acoustic meatus and the lamina of the tragus with the main portion of the cartilage of the auricle. Synonym: isthmus cartilaginis auris. (05 Mar 2000) |
| isthmus of cingulate gyrus | The narrowing of the cingulate gyrus, at its transition with the hippocampal gyrus behind and below the splenium of the corpus callosum, caused by the anterior extension of the conjoined parieto-occipital and calcarine sulci. Synonym: isthmus gyri cinguli, isthmus of gyrus fornicatus, isthmus of limbic lobe. (05 Mar 2000) |