| collateral fissure | A long, deep sagittal fissure on the undersurface of the temporal lobe, marking the border between the fusiform gyrus laterally and the hippocampal and lingual gyri medially; the great depth of the collateral sulcus results in a bulging of the floor of the occipital and temporal horn of the lateral ventricle, the collateral eminence. Synonym: sulcus collateralis, sulcus occipitotemporalis, collateral fissure, fissura collateralis, occipitotemporal sulcus. (05 Mar 2000) |
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| pit and fissure caries | Caries initiated in the areas where developmental pits and fissures are located on the tooth surface. (05 Mar 2000) |
| pit and fissure sealants | Agents used to occlude dental enamel pits and fissures in the prevention of dental caries. (12 Dec 1998) |
| portal fissure | A transverse fissure on the visceral surface of the liver between the caudate and quadrate lobes, lodging the portal vein, hepatic artery, hepatic nerve plexus, hepatic ducts, and lymphatic vessels. Synonym: caudal transverse fissure, portal fissure. (05 Mar 2000) |
| postcentral fissure | A fissure on the superior surface of the cerebellum separating the culmen from the central lobule. (05 Mar 2000) |
| posterior median fissure of spinal cord | A shallow furrow in the median line of the posterior surface of the spinal cord. Synonym: sulcus medianus posterior medullae spinalis, posterior median fissure of spinal cord. (05 Mar 2000) |
| posterior median fissure of the medulla oblongata | The longitudinal groove marking the posterior midline of the medulla oblongata; continuous below with the posterior median sulcus of the spinal cord. Synonym: sulcus medianus posterior medullae oblongatae, posterior median fissure of the medulla oblongata. (05 Mar 2000) |
| posterolateral fissure | The earliest fissure to appear in the development of the cerebellum; it separates the flocculus and nodulus from the uvula and tonsil. Synonym: fissura posterolateralis, prenodular fissure. (05 Mar 2000) |
| posthippocampal fissure | A deep fissure on the medial aspect of the cerebral cortex, extending on an arched line from the isthmus of the fornicate gyrus back to the occipital pole, marking the border between the lingual gyrus below and the cuneus above it. The cortex in the depth of the sulcus corresponds to the horizontal meridian of the contralateral half of the visual field. Synonym: sulcus calcarinus, calcarine fissure, fissura calcarina, posthippocampal fissure. (05 Mar 2000) |
| postlingual fissure | A transverse fissure on the superior vermis of the cerebellum separating the lingula from the central lobule. (05 Mar 2000) |
| postlunate fissure | A transverse fissure on the superior vermis of the cerebellum separating the posterior lunate lobule in front from the ansiform lobule behind. (05 Mar 2000) |
| postpyramidal fissure | A fissure that separates the pyramid of the cerebellum from the tuber. (05 Mar 2000) |
| postrhinal fissure | A fissure separating the hippocampal from the collateral gyrus. (05 Mar 2000) |
| prenodular fissure | The earliest fissure to appear in the development of the cerebellum; it separates the flocculus and nodulus from the uvula and tonsil. Synonym: fissura posterolateralis, prenodular fissure. (05 Mar 2000) |
| primary fissure of cerebellum | The deepest fissure of the cerebellum; demarcates the division of anterior and posterior lobes of the cerebellum; second to appear embryologically. Synonym: fissura prima cerebelli. (05 Mar 2000) |