| ostium urethrae internum | The internal opening or orifice of the urethra, at the anterior and inferior angle of the trigone. Synonym: ostium urethrae internum, internal urethral opening. (05 Mar 2000) |
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| tunica mucosa urethrae femininae | The inner mucosal layer of the female urethra. Synonym: tunica mucosa urethrae femininae. (05 Mar 2000) |
| tunica muscularis urethrae femininae | Muscular layer of the wall of the female urethra. Synonym: tunica muscularis urethrae femininae. (05 Mar 2000) |
| fossa navicularis urethrae | The terminal dilated portion of the urethra in the glans penis. Synonym: fossa navicularis urethrae, fossa terminalis urethrae, Morgagni's fossa, Morgagni's fovea. (05 Mar 2000) |
| fossa terminalis urethrae | The terminal dilated portion of the urethra in the glans penis. Synonym: fossa navicularis urethrae, fossa terminalis urethrae, Morgagni's fossa, Morgagni's fovea. (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 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) |