| laryngeal aperture | The aperture between the pharynx and larynx, bounded by the superior edges of the epiglottis (anteriorly), the aryepiglottic folds (laterally), and the mucosa between the arytenoids (posteriorly). Synonym: aditus laryngis, laryngeal aperture. (05 Mar 2000) |
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| lateral aperture of the fourth ventricle | One of the two lateral openings of the fourth ventricle into the subarachnoid space at the cerebellopontine angle. Synonym: apertura lateralis ventriculi quarti, foramen lateralis ventriculi quarti, foramen of Key-Retzius, foramen of Luschka, Retzius' foramen. (05 Mar 2000) |
| Amberg's lateral sinus line | A line dividing the angle formed by the anterior edge of the mastoid process and the temporal line. (05 Mar 2000) |
| aneurysm of sinus of Valsalva | A congenital thin-walled tubular out pouching usually in the right or non-coronary sinus with an entirely intracardiac course that may rupture into the right or rarely the left heart chambers to form an aortocardiac fistula. (05 Mar 2000) |
| aortic sinus | 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) |
| aortic sinus aneurysm | Abnormal dilation of one or more of the three aortic sinuses situated behind the three aortic valve cusps. (05 Mar 2000) |
| apertura sinus frontalis | One of a pair of openings in the floor of the frontal sinuses in the nasal part of the frontal bone, through which the frontal sinuses communicate with the ethmoidal infundibulum via the frontonasal duct. Synonym: apertura sinus frontalis. (05 Mar 2000) |
| apertura sinus sphenoidalis | One of the pair of openings in the body of the sphenoid bone through which the sphenoid sinuses communicate with the sphenoethmoidal recess of the nasal cavity. Synonym: apertura sinus sphenoidalis, sphenoidal sinus aperture. (05 Mar 2000) |
| arrhythmia, sinus | Irregularity of the heart rate related to functioning of the sinoatrial node. (12 Dec 1998) |
| barotrauma, sinus | See: Barosinusitis. (12 Dec 1998) |
| basilar sinus | A venous plexus on the clivus, connected with the cavernous and petrosal sinuses and the internal vertebral (epidural) venous plexus. Synonym: plexus basilaris, basilar sinus. (05 Mar 2000) |
| Breschet's sinus | A paired dural venous sinus beginning on the parietal bone, running along the sphenoidal ridges and emptying into the cavernous sinus. Synonym: sinus sphenoparietalis, Breschet's sinus, sinus alae parvae. (05 Mar 2000) |
| Valsalva's sinus | 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) |
| valve of coronary sinus | A delicate fold of endocardium at the opening of the coronary sinus into the right atrium. Synonym: valvula sinus coronarii, coronary valve, thebesian valve. (05 Mar 2000) |
| valvula sinus coronarii | A delicate fold of endocardium at the opening of the coronary sinus into the right atrium. Synonym: valvula sinus coronarii, coronary valve, thebesian valve. (05 Mar 2000) |