| diaphragm sellae | A fold of dura mater extending transversely across the sella turcica and roofing over the hypophyseal fossa; it is perforated in its centre for the passage of the infundibulum. Synonym: diaphragma sellae, diaphragm sellae, tentorium of hypophysis. (05 Mar 2000) |
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| inferior fascia of pelvic diaphragm | The fascia that covers the inferior aspect of the levator ani and coccygeus muscles. Synonym: fascia diaphragmatis pelvis inferior, anal fascia. (05 Mar 2000) |
| inferior fascia of urogenital diaphragm | The layer of fascia extending between the ischiopubic rami inferior to the sphincter urethrae and the deep transverse perineal muscles. Synonym: membrana perinei, fascia diaphragmatis urogenitalis inferior, Camper's ligament, ligamentum triangulare, perineal membrane, triangular ligament. (05 Mar 2000) |
| iris diaphragm | <microscopy> A diaphragm with thin metal leaves so arranged that the rotation of an actuating lever varies the diameter. (05 Aug 1998) |
| eventration of the diaphragm | Extreme elevation of a half or part of the diaphragm, which is usually atrophic and abnormally thin. (05 Mar 2000) |
| urogenital diaphragm | A triangular sheet of muscle between the ischiopubic rami; composed of the sphincter urethrae, and the deep transverse perineal muscles. Synonym: diaphragma urogenitale. (05 Mar 2000) |
| field diaphragm | <microscopy> In a photomicrographic system particularly, an iris diaphragm that is imaged in the field of view with Kohler illumination. This limits the extent of the illuminated field and eliminates much extraneous light. The iris diaphragm that is located in front of the collecting lens of the light source. With Kohler illumination, the condenser focuses the image of the field diaphragm onto the image plane. (05 Aug 1998) |
| left crus of diaphragm | The muscular origin of the diaphragm from the upper two or three lumbar vertebrae that ascends to the left of the aorta to reach the central tendon. Synonym: crus sinistrum diaphragmatis. (05 Mar 2000) |
| lumbar part of diaphragm | The portion of the diaphragm that arises from the upper lumbar vertebrae and from the medial and lateral arcuate ligaments. See: right crus of diaphragm, left crus of diaphragm, lateral arcuate ligament, medial arcuate ligament. Synonym: pars lumbalis diaphragmatis, vertebral part of diaphragm. (05 Mar 2000) |
| angle of aperture | <ophthalmology, optics> The angle formed by lines drawn from the ends of the diameter of a lens to its point of focus. See: angular aperture. (05 Mar 2000) |
| angular aperture | The angle, in air, of light that passes from the object to the ends of the diameter of the front lens of the microscope objective. (05 Mar 2000) |
| anterior nasal aperture | The anterior nasal opening in the skull. Synonym: apertura piriformis, piriform opening. (05 Mar 2000) |
| aperture | <physics> The opening in an optical system which restricts the size of the bundle of rays incident on a given surface. (Usually circular and specified by diameter.) (09 Oct 1997) |
| aperture, angular | <microscopy> The angle between the most divergent rays that can pass through a lens to form the image of an object. The angle subtended between the axis of a lens and the largest accepted angle of the image-forming rays. With microscope objectives the trigonometric sine of this angle is used to define numerical aperture but as measured from the axial object point. (05 Aug 1998) |
| aperture correction | <microscopy> An electronic process used in some high-resolution video cameras and monitors that compensates for the loss in sharpness of detail due to the finite dimensions (aperture) of the scanning beam. (05 Aug 1998) |