| simian 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) |
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| sphenoidal fissure | A cleft between the greater and the lesser wings of the sphenoid establishing a channel of communication between the middle cranial fossa and the orbit, through which pass the oculomotor and trochlear nerves, the ophthalmic division of the trigeminal nerve, the abducens nerve, and the ophthalmic veins. Synonym: fissura orbitalis superior, foramen lacerum anterius, sphenoidal fissure. (05 Mar 2000) |
| sphenomaxillary 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) |
| sphenopetrosal fissure | A narrow fissure between the undersurface of the greater wing of the sphenoid and the petrous portion of the temporal bone. Synonym: fissura sphenopetrosa. (05 Mar 2000) |
| squamotympanic fissure | The fissure separating the tympanic part of the temporal bone from the squamous part; it is continuous medially with the petrotympanic fissure and the petrosquamous fissure. Synonym: fissura tympanosquamosa, tympanosquamous fissure. (05 Mar 2000) |
| superior orbital fissure | A cleft between the greater and the lesser wings of the sphenoid establishing a channel of communication between the middle cranial fossa and the orbit, through which pass the oculomotor and trochlear nerves, the ophthalmic division of the trigeminal nerve, the abducens nerve, and the ophthalmic veins. Synonym: fissura orbitalis superior, foramen lacerum anterius, sphenoidal fissure. (05 Mar 2000) |
| decidual fissure | A cleft in the decidua basalis or placenta. (05 Mar 2000) |
| superior temporal fissure | The longitudinal sulcus that separates the superior and middle temporal gyri. Synonym: sulcus temporalis superior, superior temporal fissure. (05 Mar 2000) |
| 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) |
| 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) |
| 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) |