The brain longitudinal fissure is the deepest groove of the cerebral cortex. It runs from front to back, dividing the cerebrum lengthwise into two encephalic halves; the left cerebral hemisphere, and the right hemisphere. However, this sulcus (groove) does not go all the way down as it ends up at the corpus callosum, which is the thick white bundle of myelinated fibers that connect them to one another.
The longitudinal fissure of the human brain measures between 3 and 5 cm deep. Inside it, there are the two cerebral cortex internal surfaces, one for each hemisphere. The internal (medial) surface, like the external surface of cortex, is characterized by a series of secondary grooves called sulcus (plural sulci), which mark off smaller structures called gyri (sing. gyrus), such as the cingulate gyrus which surrounds the corpus callosum.
The brain longitudinal fissure allow the partial entrance into the cerebrum by the three layers of the meninges; dura mater, arachnoid, and pia mater, and, with them, the cerebrospinal fluid.
Below, superior view of human brain and its two hemispheres divided by the longitudinal fissure.
