| LSO | lateral superior olive; left salpingo-oophorectomy; left superior oblique; lumbosacral orthosis |
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| CTR | Cardio-Thoracic Ratio |
| MURCS Associations | MUllerian duct aplasia, Renal aplasia, Cervico-thoracic vertebral(Somite) dysplasia Associations |
| AATS | American Association for Thoracic Surgery |
| ADT | Accepted Dental Therapeutics; adenosine triphosphate; admission, discharge, transfer; agar-gel diffu... |
| aperture of orbit | The somewhat quadrangular anterior entrance to the orbit which forms the base of the pyramid-shaped orbital cavity. It is bounded by the sharp supra-, infra-, and lateral orbital margins and a less obvious medial margin on each side of the upper nose. Synonym: aditus orbitae, aperture of orbit. (05 Mar 2000) |
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| aperture plane | <microscopy> In a microscope adjusted for Koehler illumination, the conjugate planes that include the light source, the condenser iris diaphragm, the objective lens back aperture, and the eye point. Spaces in the aperture planes are the reciprocal of those in the field planes. (05 Aug 1998) |
| back aperture | <microscopy> The exit pupil of a microscope objective lens. The objective lens back aperture, which can be examined with a phase telescope or by inserting a Bertrand lens, displays the conoscopic interference figure and diffraction patterns. (05 Aug 1998) |
| relative aperture | <microscopy> The ratio of the focal length of a lens to the diameter of its entrance pupil. This gives a number known as the f-number, usually written f:8, f:16, etc. Thus, if the focal length is divided by the number 8, 16, etc., the result will be the diameter of the entrance pupil of the lens, or if the diaphragm of the lens is wide open it will be very nearly the diameter of the free aperture of the lens. See: F-number. (05 Aug 1998) |
| medial aperture of the fourth ventricle | The large midline opening in the posterior inferior part of the roof of the fourth ventricle, connecting the ventricle with the cerebellomedullary cistern. Synonym: apertura mediana ventriculi quarti, arachnoid foramen, Magendie's foramen, median aperture of the fourth ventricle. (05 Mar 2000) |
| median aperture of the fourth ventricle | The large midline opening in the posterior inferior part of the roof of the fourth ventricle, connecting the ventricle with the cerebellomedullary cistern. Synonym: apertura mediana ventriculi quarti, arachnoid foramen, Magendie's foramen, median aperture of the fourth ventricle. (05 Mar 2000) |
| contra-aperture | A second opening made at the dependent part of an abscess or other cavity containing fluid, which is not draining satisfactorily through an opening previously made. Synonym: contra-aperture, counterpuncture. (05 Mar 2000) |
| pyriform aperture wiring | A method of wiring using the nasal bones at the area of the pyriform aperture for the stabilization of fractures of the jaw. (05 Mar 2000) |
| sphenoidal sinus aperture | 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) |
| numerical aperture | For a lens the resolving power depends upon the wavelength of light being used and inversely upon the numerical aperture. The N.A. Is the product of the refractive index of the medium (1 for air, 1.5 for immersion oil) and the sine of the angle, i, the semi angle of the cone formed by joining objects to the perimeter of the lens. The larger the value of N.A., the better the resolving power of the lens, most objectives have their N.A. Value engraved on the barrel and this should be quoted when describing an optical system. (18 Nov 1997) |
| inferior pelvic aperture | The lower opening of the true pelvis, bounded anteriorly by the pubic arch, laterally by the rami of the ischium and the sacrotuberous ligament on either side, and posteriorly by these ligaments and the tip of the coccyx. Synonym: apertura pelvis inferior, apertura pelvis minoris, fourth parallel pelvic plane, pelvic outlet, pelvic plane of outlet, plane of outlet. (05 Mar 2000) |
| external aperture of cochlear canaliculus | The external opening of the cochlear aqueduct on the temporal bone medial to the jugular fossa. Synonym: apertura externa canaliculi cochleae. (05 Mar 2000) |
| external aperture of vestibular aqueduct | The external opening of the vestibular aqueduct on the posterior surface of the petrous part of the temporal bone near the groove for the sigmoid sinus. Synonym: apertura externa aqueductus vestibuli. (05 Mar 2000) |
| 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) |
| 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) |