Corpus callosum: largest commissure of the brain, connecting the neocortex of the two cerebral hemispheres.
Length: about 10 cm (nearly half the anteroposterior length of the hemisphere)
Made up of 150 to 200 million fibres
It connects all parts of the neocortex of the two hemispheres except the lower and anterior parts of the temporal lobes, which are connected instead by the anterior commissure.
External Features and Relations
Forms an arched interhemispheric bridge in the floor of the longitudinal cerebral fissure, roofing both lateral ventricles; C-shaped in sagittal section.
Lies closer to the frontal pole (4 cm behind) than the occipital pole (6 cm in front).
Concave inferior aspect: attaches to the fornix via the septum pellucidum.
Convex superior aspect: covered by a thin grey layer, the indusium griseum (with medial and lateral longitudinal striae).
Superior aspect is covered on each side by the cingulate gyrus, separated from it by the callosal sulcus; anterior cerebral vessels commonly lie on the pia mater over the superior aspect.