| fissure sign | In perfusion scintigraphy of the lungs, decreased uptake of radionuclide in the periphery of each lobe, making the fissures visible; caused by a variety of diseases and artifacts. (05 Mar 2000) |
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| lateral cerebral fissure | The deepest and most prominent of the cortical fissures, extending from the anterior perforated substance first laterally at the deep incisure between the frontal and temporal lobes, then back and slightly upward over the lateral aspect of the cerebral hemisphere, with the superior temporal gyrus as its lower bank, the insula forming its greatly expanded floor. Two short side branches, the ramus anterior and ramus ascendens, divide the inferior frontal gyrus into an orbital part, triangular part, and opercular part. Synonym: sulcus lateralis cerebri, fissura cerebri lateralis, lateral cerebral fissure, sylvian fissure, fissure of Sylvius. (05 Mar 2000) |
| left sagittal fissure | A sagittal groove on the undersurface of the liver formed by the fissura ligamenti teretis anteriorly and the fissura ligamenti venosi posteriorly. (05 Mar 2000) |
| linguogingival fissure | A fissure sometimes occurring on the lingual surface of one of the upper incisors and extending into the cementum. (05 Mar 2000) |
| longitudinal fissure of cerebrum | The deep cleft separating the two hemispheres of the cerebrum. Synonym: fissura longitudinalis cerebri, great longitudinal fissure. (05 Mar 2000) |
| lunate fissure | A small, inconstant semilunar groove on the cortical convexity near the occipital pole, marking the anterior border of the striate cortex (area 17) and considered homologous with the major sulcus of the same name that is a more constant feature of the cerebral cortex in monkeys and apes. Synonym: sulcus lunatus cerebri, ape fissure, lunate fissure, lunate sulcus, simian fissure. (05 Mar 2000) |