gyrus (ji'rus), pi., gyri

Lit., a ring or circle. _ i. The scala tympani and scala vestibuli. 2. See convolution (2d def.). 3. One turn in a spiral structure, angular g. The g. about the dorsal end of the super temporal fi ure, annectant gyri. Any one of the four gyri which act as a connection between the occipital and parietotemporal lobes of the brain. basirrhinal g. Of Wilder, the g. at or near the tip of the temporal lobe, between the hippocampal and amygdaline fi ures, callosal g. See g. fomaticus. gyri cerebelli. The laminae of the cerebellum, gyrus cerebri. A cerebral convolution, gyrus chorioides. Syn.: anterior choroid convolution. In the embryo the convexity of the parietes of the lateral rece of the fourth ventricle, gyri cochleae. The gyri of the cochlea of the internal ear. g. descend ens. The narrow area at the extremity of the occipital lobe, just below the post calcarine fi ure, g. fornicatus. Syn.: callosal convolution. The g. which borders the corpus callosum. g. hippocampi. See uncinate g. gyri poster i ores infer i ores. Syn.: Arnold's convolution. Of Arnold, gyri on the ventral or tentorial aspect of the occipitotemporal lobe. g. rectus. Syn.: entorhynnal fold. The narrow gyrus on the orbital aspect of the frontal lobe, between the mesal margin and the olfactory fi ure, hippocampal g. The g. between the hippocampal and collateral fi ures, extending from the splenium to the uncinate g. mediofrontal g. The g. between the superfrontal and sub frontal fi ures, sometimes subdivided by a med i frontal fi ure. mediotemporal g. The g. between the super temporal and med i temporal fi ures. orbitalbital orgyri. ventral The divisions surface of the of the or frontal lobe. para central g. The oval or quadrilateral area on the mesal aspect of the cerebrum, just cephalad of the pre cuneus, post central g. Syn.: medial fold. The g. between the central and post central fi ures, posteroparietal g. See ascending parietal convolution, under convolution. pre central g. The g. between the central fi ure and the pre central and super central fi ures. cere primary brum demarcated the fetal by the of primary gyri. Areas fi ures. straight g. See rectus g. supra marginal g. See marginal convolution, under convolution, uncinate g. The continuation forward of the hippocampal g. [Gr., gyros, ring, circle.] H. Symbol for the element hydrogen. Abbreviation of haustus, a draft; in ophthalmology, abbreviation for hypermetropia.