- 1. Anything resembling a lid or cover. 2. [TA] In anatomy, the portions of the frontal (o. frontale [TA], frontal o. [TA]), parietal (o. parietale [TA], parietal o. [TA]), and temporal (o. temporale [TA], temporal o. [TA]) lobes bordering the lateral sulcus and covering the insula. 3. In parasitology, the lid or caplike cover of the shell opening of operculated freshwater snails in the subclass Prosobranchiata, and of the eggs of certain trematode and cestode parasites. 4. The attached flap in the tear of retinal detachment. 5. The mucosal flap partially or completely covering an unerupted tooth. [L. cover or lid, fr. operio, pp. opertus, to cover]- o. ilei SYN: ileal sphincter.- occipital o. a portion of the occipital lobe of the brain demarcated by the simian fissure (sulcus lunatus) when present in humans.- trophoblastic o. the mushroom-shaped plug of fibrin that fills the aperture in the endometrium made by the implanting ovum.
* * *oper·cu·lum ō-'pər-kyə-ləm n, pl -la -lə also -lums any of several parts of the cerebrum bordering the sylvian fissure and concealing the insula
* * *n. (pl. opercula)1. a plug of mucus that blocks the cervical canal of the uterus in a pregnant woman. When the cervix begins to dilate at the start of labour, the operculum, slightly stained with blood, comes away as a discharge ('show').2. (in embryology) a plug of fibrin and blood cells that develops over the site at which a developing fertilized ovum has become embedded in the wall of the uterus.3. (in neurology) one of the folded and overlapping regions of cerebral cortex that conceal the insula on each side of the brain.
* * *oper·cu·lum (o-purґku-ləm) pl. operґcula [L.] 1. a lid or covering structure. 2. one of the insular opercula (q.v.). 3. in fungi, a small cap on an ascus that pops open when the mature organism is ready to eject its spores.
Medical dictionary. 2011.