| sylvian 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) |
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| dental fissure | <dentistry> Deep grooves or clefts in the surface of teeth equivalent to class 1 cavities in black's classification of dental caries. (12 Dec 1998) |
| dentate fissure | A shallow groove between the dentate gyrus and the parahippocampal gyrus; the remains of a fissure extending deep into the hippocampus between Ammon's horn and the dentate gyrus which becomes obliterated during foetal development. Synonym: sulcus hippocampi, dentate fissure, fissura dentata, fissura hippocampi, hippocampal fissure. (05 Mar 2000) |
| inferior accessory fissure | The fissure that commonly separates the medial basal segment of the right lower lobe of the lung from the other basal segments, seen as an oblique line near the right heart border on chest radiographs. (05 Mar 2000) |
| inferior orbital fissure | A cleft between the greater wing of the sphenoid and the orbital plate of the maxilla, through which pass the maxillary division and the orbital branch of the trigeminal nerve, fibres from the pterygopalatine (Meckel's) ganglion, and the infraorbital vessels. Synonym: fissura orbitalis inferior, sphenomaxillary fissure. (05 Mar 2000) |
| oblique fissure | The deep fissure in each lung that runs obliquely downward and forward. It divides the upper and lower lobes of the left lung and separates the upper and middle lobes from the lower lobe of the right lung. Synonym: fissura obliqua pulmonis, major fissure, oblique fissure. (05 Mar 2000) |
| oblique fissure of lung | The deep fissure in each lung that runs obliquely downward and forward. It divides the upper and lower lobes of the left lung and separates the upper and middle lobes from the lower lobe of the right lung. Synonym: fissura obliqua pulmonis, major fissure, oblique fissure. (05 Mar 2000) |
| optic fissure | In the embryo, the temporary gap in the ventral margin of the developing optic cup. Synonym: choroid fissure, choroid fissure, choroidal fissure. (05 Mar 2000) |
| oral fissure | The mouth slit; the aperture of the mouth. Synonym: oral fissure. (05 Mar 2000) |
| Ecker's fissure | A fissure between the petrous part of the temporal bone and the basilar part of the occipital bone that extends anteromedially from the jugular foramen; includes the jugular foramem (at its posterior end). Synonym: fissura petro-occipitalis, Ecker's fissure. (05 Mar 2000) |
| enamel fissure | A deep cleft between adjoining cusps affording retention to caries-producing agents. (05 Mar 2000) |
| transverse fissure of cerebellum | The cleft caused by the protrusion of the anterior lobe of the cerebellum over the superior and middle cerebellar peduncles. Synonym: fissura transversa cerebelli. (05 Mar 2000) |
| transverse fissure of cerebrum | The triangular space between the corpus callosum and fornix above and the dorsal surface of the thalamus below, which is bounded laterally by the choroid fissure of the lateral ventricle, lined by pia mater, and opens caudally into the cistern of the great cerebral vein of the subarachnoid space. Synonym: fissura transversa cerebri. (05 Mar 2000) |
| transverse fissure of the lung | The deep fissure that separates the upper and middle lobes of the right lung. Synonym: fissura horizontalis pulmonis dextri, horizontal fissure of right lung, minor fissure. (05 Mar 2000) |
| tympanomastoid fissure | A fissure separating the tympanic portion from the mastoid portion of the temporal bone; it transmits the auricular branch of the vagus nerve. Synonym: fissura tympanomastoidea, auricular fissure, tympanomastoid suture. (05 Mar 2000) |