. Anatomy, descriptive and applied. Anatomy. THE CEREBRAL HEMISPHERES 921 orbital surface is marlved by a fissural system (^sulci orhitales) that is usually of zygal type, H-shaped or K-shaped, quadriradiate, or, rarely, triradiate. Wlien tlie transverse element is sufficiently pronounced it merits the name of transorbital fissure, demarcating the preorbital from the postorbital gyral field. Gyres of the Frontal Lobe (lobus frontalis). 1. Lateral Surface.—The pre- central gyre {gyrus centralis anterior), one of the chief motor areas of the cerebi-al cortex, is a moderately sinuous gyre extendi
. Anatomy, descriptive and applied. Anatomy. THE CEREBRAL HEMISPHERES 921 orbital surface is marlved by a fissural system (^sulci orhitales) that is usually of zygal type, H-shaped or K-shaped, quadriradiate, or, rarely, triradiate. Wlien tlie transverse element is sufficiently pronounced it merits the name of transorbital fissure, demarcating the preorbital from the postorbital gyral field. Gyres of the Frontal Lobe (lobus frontalis). 1. Lateral Surface.—The pre- central gyre {gyrus centralis anterior), one of the chief motor areas of the cerebi-al cortex, is a moderately sinuous gyre extending from the dorsimesal border to the sylvian fissure and demarcated by the central and the precentral fissures (supercentral + precentral).. G, = GYRE FISSURE E. A. S. Fig. 679.—Fissures and gyres of the mesal surface of the left hemicerebrum. The superfrontal gyre is limited laterally by the superfrontal fissure, while it is continuous over the dorsimesal border with its mesal surface.' It merges insensibly with the medifrontal gyre in the prefrontal region, while it may be partially subdivided by the paramesal fissure. The medifrontal gyre {gyrus frontalis medius) is broader than the preceding, demarcated by the superfrontal and subfrontal fissures, and often marked by the medifrontal fissure in its prefrontal portion. The subfrontal gyre {gyrus frontalis inferior) is limited by the subfrontal fissure and the basisylvian + sylvian proper. It is traversed by the presylvian and sub- sylvian rami, embracing the preoperculum or pars triangularis. The gyre is of historic importance since Broca, in 1861, declared it to be the seat of speech con- trol. (See Cerebral Localization.) 2. Mesal Surface.—On the mesal surface of the frontal lobe and embracing the dorsal end of the central fissure lies an oval lobule or gyre called the paracentral gyre (lobulus paracentralis), limited by the paracentral fissure with its caudal and cephalic limbs. Frontad tliereof extends the large
Size: 2050px × 1219px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
