Sulci and Gyri of The Frontal Lobe

Perhaps the most distinguishing feature of the external cerebral surface is the matter made up in a series of convolutions called "gyri" (singular, "gyrum"), between which are grooves of varying depth called "sulci" (singular, "sulcum") or fissures. The frontal lobe is crossed over by three sulci, which divide it into four gyri. These are the "precentral," "superior frontal," and "inferior frontal sulci" and the "precentral," "superior frontal," "middle frontal," and "inferior frontal gyri." In the middle, the frontal lobe stretches from the frontal pole along an arbitrary line that extends down from the upper border of the cerebrum, from which the central sulcus curves back to the middle surface, through the "paracentral lobule" and cingulate gyrus to the sulcus of the corpus callosum, near the midpoint of the colossal trunk. The "medial frontal gyrus" is separated below from the portion of the cingulate gyrus within the frontal lobe by the cingulate sulcus, while the back end of the medial frontal gyrus and the front half of the paracentral lobule are separated by a rising branch of the cingulate sulcus that is called the paracentral sulcus. Behind the "subcallosal area," between the "lamina terminalis" and the "posterior parolfactory sulcus," is the "paraterminal gyrus," which forms the continuation of the "indusium griseum," a thick lamina of gray matter that overlies the top surface of the corpus callosum.