- A cleft or groove. A fissure can be normal or abnormal. A fissure in the cerebral cortex is a normal feature. It is a deep fold that involves the entire thickness of the brain wall. A fissure in the anus is distinctly abnormal. It is a painful crack in the edge of the anus and is very painful. Also called an anal fissure or fissure in ano.
* * *1. A deep furrow, cleft, or slit.(For most of the brain fissures, see entries under sulcus). 2. In dentistry, a developmental break or fault in the tooth enamel. SYN: fissura (1) [TA]. [L. fissura]- abdominal f. congenital failure of the ventral body wall to close. SEE ALSO: celosomia, gastroschisis.- ansoparamedian f. [TA] the f. separating lobule HVIIA, crus II of the ansiform lobule, from lobule HVIIB, the paramedian lobule, of the posterior lobe of the cerebellum. SYN: fissura intersemilunaris [TA], intersemilunar f..- anterior median f. of medulla oblongata [TA] the longitudinal groove in the midline of the anterior aspect of the medulla oblongata; it is the medullary equivalent of the anterior median f. of the spinal cord and ends at the foramen cecum posterius; its caudal part is obliterated by the decussation of the pyramids. SYN: fissura mediana anterior medullae oblongatae [TA], anteromedian groove (1).- anterior median f. of spinal cord [TA] a deep median f. on the anterior surface of the spinal cord. SYN: fissura mediana anterior medullae spinalis [TA], anteromedian groove (2), sulcus ventralis.- antitragohelicine f. SYN: fissura antitragohelicina.- azygos f. the four-layered pleural fold that separates an azygos lobe from the rest of the right upper lobe of the lung, seen as an oblique line curving down from the right apex toward the mediastinal shadow on a chest radiograph. The azygos vein is projected as a teardrop shadow at the inferior end of the azygos f..- Bichat f. the nearly circular f. corresponding to the medial margin of the cerebral (pallial) mantle, marking the hilus of the cerebral hemisphere, consisting of the callosomarginal f. and choroidal f. along the hippocampus, both of which are continuous with the stem of the f. of Sylvius at the anterior extremity of the temporal lobe.- cerebellar fissures the deep furrows which divide the lobules of the cerebellum. SEE ALSO: postcentral f., primary f. of cerebellum, secondary f. [TA] of cerebellum. SYN: fissurae cerebelli [TA].- cerebral fissures the variously named fissures of the cerebral hemispheres. SEE ALSO: sulci cerebri, under sulcus.- choroid f. SYN: optic f..- choroidal f. [TA] 1. SYN: optic f.. 2. the narrow cleft along the medial wall of the lateral ventricle along the margins of which the choroid plexus is attached; it lies between the upper surface of the thalamus and lateral edge of the fornix in the central part of the ventricle and between the terminal stria and fimbria hippocampi in the inferior horn;- glaserian f. SYN: petrotympanic f..- great horizontal f. SYN: horizontal f. [TA] of cerebellum.- Henle fissures minute spaces filled with connective tissue between the muscular fasciculi of the heart.- horizontal f. [TA] of cerebellum horizontal f. that divides the ansiform lobule into its major parts, crus I (superior semilunar lobule) and crus II (inferior semilunar lobule). SYN: fissura horizontalis [TA], great horizontal f..- inferior accessory f. the f. that commonly separates the medial basal segment of the right lower lobe of the lung from the other basal segments, occasionally seen as an oblique line near the right heart border on chest radiographs.- inferior orbital f. [TA] 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, fibers from the pterygopalatine (Meckel) ganglion, and the infraorbital vessels. SYN: fissura orbitalis inferior [TA], sphenomaxillary f..- intersemilunar f. [offalt TA] SYN: ansoparamedian f..- intraculminate f. [TA] the f. located within the culminate lobule separating lobule IV from lobule V in the anterior lobe of the cerebellum and extending to the lateral margin of the cerebellum. SYN: fissura intraculminalis [TA].- left sagittal f. a sagittal groove on the undersurface of the liver formed by the f. for round ligament anteriorly and the f. for ligamentum venosum posteriorly.- f. for ligamentum teres [TA] a cleft on the inferior surface of the liver, running from the inferior border to the left extremity of the porta hepatis; it lodges the round ligament of the liver. SYN: fissura ligamenti teretis hepatis [TA], f. for round ligament of liver, fossa venae umbilicalis, umbilical f., umbilical fossa.- f. for ligamentum venosum [TA] a deep cleft extending from the porta hepatis and the inferior vena cava between the left lobe and the caudate lobe; it lodges the ligamentum venosum and is thus a vestige of the fossa of the ductus venosus. SYN: fissura ligamenti venosi [TA], f. of venous ligament.- linguogingival f. a f. sometimes occurring on the lingual surface of one of the upper incisors and extending into the cementum.- fissures of liver left sagittal f., right sagittal f., porta hepatis, f. for ligamentum teres, f. for ligamentum venosum.- longitudinal cerebral f. [TA] the deep cleft separating the two hemispheres of the cerebrum. SYN: fissura longitudinalis cerebri [TA], great longitudinal f..- oblique f. of lung [TA] the deep f. 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. SYN: fissura obliqua pulmonis [TA], major f., oblique f..- optic f. in the embryo, the temporary gap in the ventral margin of the developing optic cup. SYN: choroidal f. (1) [TA], fissura choroidea [TA], choroid f..- Pansch f. a cerebral f. (sulcus) running from the lower extremity of the central f. (sulcus) nearly to the end of the occipital lobe.- petrooccipital f. [TA] a f. 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 foramen (at its posterior end). SYN: fissura petro- occipitalis [TA], Ecker f..- petrosphenoidal f. [TA] highly variable opening between the medial portion of the posterior border of the greater wing of the sphenoid bone (posterior to foramen ovale) and the medial portion of the anterior border of the petrous part of the temporal bone; it may be seen as a wide, lateral extension of the foramen lacerum in the dry skull, or it may be closed, especially laterally, taking the form of a petrosphenoidal suture rather than a f.. SYN: fissura sphenopetrosa [TA], sphenopetrosal f..- petrosquamous f. [TA] a shallow f. indicating externally the line of fusion of the petrous and squamous portions of the temporal bone. SYN: fissura petrosquamosa [TA].- petrotympanic f. [TA] a f. between the tympanic and petrous portions of the temporal bone; it transmits the chorda tympani nerve through a small patent portion, the anterior canaliculus of the chorda tympani. SYN: fissura petrotympanica [TA], glaserian f..- portal f. SYN: porta hepatis.- postcentral f. a f. on the superior surface of the cerebellum separating the culmen from the central lobule.- posterior superior f. [TA] the f. located between lobules VI and VII of the posterior lobe of the cerebellum and extending to the lateral margin of the cerebellum. SYN: fissura posterior superior [TA].- posterolateral f. [TA] the earliest f. to appear in the development of the cerebellum; it separates the flocculus and nodulus from the uvula and tonsil. SYN: fissura posterolateralis [TA], prenodular f..- posthippocampal f. SYN: calcarine sulcus.- postlingual f. a transverse f. on the superior vermis of the cerebellum separating the lingula from the central lobule.- postlunate f. a transverse f. on the superior vermis of the cerebellum separating the posterior lunate lobule in front from the ansiform lobule behind.- precentral f. [TA] the f. located between the anterior and posterior parts (lobules II and III) of the central lobule of the anterior lobe of the cerebellum; extends from the vermis to the cerebellar margin; precentral f. a is found between lobule I and lobule II, the latter of which forms the anterior part of the central lobule. SYN: fissura precentralis [TA].- preculminate f. [TA] the f. located between lobules III and IV of the anterior lobe of the cerebellum, representing the f. between the central lobule and culmen; extends from the vermis to the cerebellar margin. SYN: fissura preculminalis [TA].- prenodular f. SYN: posterolateral f..- prepyramidal f. [TA] the f. located between lobules VIIB and VIII of the posterior lobe of the cerebellum; continues from the vermis into the hemisphere where it separates lobule HVIIB from HVIIIA. SYN: fissura prepyramidalis [TA].- primary f. of cerebellum [TA] the deepest f. of the cerebellum; demarcates the division of anterior and posterior lobes of the cerebellum; second to appear embryologically. SYN: fissura prima cerebelli [TA].- pterygomaxillary f. [TA] the narrow gap between the lateral pterygoid plate and the infratemporal surface of the maxilla through which the infratemporal fossa communicates with the pterygopalatine fossa; gives passage to the third part of the maxillary artery and the posterior superior alveolar arteries, veins and nerves. SYN: fissura pterygomaxillaris [TA], fissura pterygopalatina.- right sagittal f. a sagittal groove on the undersurface of the liver formed by the fossa for gallbladder anteriorly and the groove for vena cava posteriorly.- f. of Rolando SYN: central sulcus.- secondary f. [TA] of cerebellum a f. that separates the uvula of the inferior vermis of the cerebellum from the pyramid. SYN: fissura secunda cerebelli [TA].- simian f. SYN: lunate sulcus.- sphenopetrosal f. SYN: petrosphenoidal f..- squamotympanic f. SYN: tympanosquamous f..- superior orbital f. [TA] 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. SYN: fissura orbitalis superior [TA], foramen lacerum anterius, sphenoidal f..- transverse f. of cerebellum the cleft caused by the protrusion of the anterior lobe of the cerebellum over the superior and middle cerebellar peduncles. SYN: fissura transversa cerebelli.- transverse cerebral f. [TA] 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 f. of the lateral ventricle, lined by pia mater, and opens caudally into the cistern of the great cerebral vein of the subarachnoid space. SYN: fissura transversa cerebri [TA].- transverse f. of the right lung [TA] the deep f. that separates the upper and middle lobes of the right lung. SYN: fissura horizontalis pulmonis dextri [TA], horizontal f. of right lung, minor f..- tympanomastoid f. [TA] a f. separating the tympanic portion from the mastoid portion of the temporal bone; it transmits the auricular branch of the vagus nerve. SYN: fissura tympanomastoidea [TA], auricular f., tympanomastoid suture.- tympanosquamous f. [TA] the f. separating the tympanic part of the temporal bone from the squamous part; it is continuous medially with the petrotympanic f. and the petrosquamous f.. SYN: fissura tympanosquamosa [TA], squamotympanic f..- vestibular f. of cochlea a fine f. in the lower part of the first turn of the cochlea, formed by a spiral lamina which projects from the outer wall of the cochlea but does not quite reach the osseous spiral lamina, thus leaving a narrow gap.- zygal f. a figure formed by two nearly parallel cerebral fissures connected by a short f. at right angles, forming an H.
* * *fis·sure 'fish-ər, Brit also 'fish-yu̇r n1) a natural cleft between body parts or in the substance of an organ: asa) any of several clefts separating the lobes of the liverb) any of various clefts between bones or parts of bones in the skullc) any of the deep clefts of the brain esp one of those located at points of elevation in the walls of the ventricles compare SULCUSd) ANTERIOR MEDIAN FISSURE also POSTERIOR MEDIAN SEPTUM2) a break or slit in tissue usu. at the junction of skin and mucous membrane <\fissure of the lip>3) a linear developmental imperfection in the enamel of a toothfis·sured 'fish-ərd, Brit also 'fish-yu̇rd adj
* * *n.1. (in anatomy) a groove or cleft; e.g. the fissure of Sylvius is the groove that separates the temporal lobe of the brain from the frontal and parietal lobes.2. (in pathology) a cleftlike defect in the skin or mucous membrane caused by some disease process. See anal fissure.3. (in dentistry) a naturally occurring groove in the enamel on the surface of a tooth, especially a molar. It is a common site of dental caries.
* * *fis·sure (fishґər) [L. fissura, q.v.] 1. fissura. any cleft, groove, or sulcus, normal or otherwise. 2. a deep cleft in the tooth surface, usually due to imperfect fusion of the enamel of the adjoining dental lobes. Cf. pit. Considered as belonging to Class I in the Black classification (see table at caries). Called also enamel f.
For descriptions of specific anatomic structures not listed here, see under fissura.
Medical dictionary. 2011.