| medionecrosis aortae idiopathica cystica | Loss of elastic and muscle fibres in the aortic media, with accumulation of mucopolysaccharide, sometimes in cystlike spaces between the fibres; a disease of unknown cause, which may be inherited and which predisposes to dissecting aneurysms. Synonym: Erdheim disease, medionecrosis aortae idiopathica cystica, medionecrosis of the aorta, mucoid medial degeneration. (05 Mar 2000) |
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| sinus aortae | The space between the superior aspect of each cusp of the aortic valve and the dilated portion of the wall of the ascending aorta, immediately above each cusp. Synonym: sinus aortae, Petit's sinus, Valsalva's sinus. Arlt's sinus, an inconstant depression on the lower portion of the internal surface of the lacrimal sac. Barber's pilonidal sinus, pilonidal sinus occurring in barbers, usually in the web between the fingers, due to the burying of exogenous hairs by the alternate loosening and tightening of tissues of the hand by the manipulation of scissors. (05 Mar 2000) |
| ostium aortae | The opening from the left ventricle into the ascending aorta; it is guarded by the aortic valve. Synonym: ostium aortae, aortic ostium. (05 Mar 2000) |
| Vieussens' isthmus | A muscular ring surrounding the fossa ovalis in the wall of the right atrium of the heart. Synonym: annulus ovalis, margin of fossa ovalis, Vieussens' annulus, Vieussens' isthmus, Vieussens' limbus, Vieussens' ring. (05 Mar 2000) |
| 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) |
| 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 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) |