Longitudinal fissure Longitudinal fissure The longitudinal fissure (or cerebral fissure, median longitudinal fissure, or interhemispheric fissure) is the deep groove that separates the two hemispheres of the vertebrate brain. The medial surfaces of the two hemispheres are as similarly convoluted by gyri and sulci as is the outer surface of the brain. It is thought that a majority of existing animals, including Homo sapiens, have evolved from a common wormlike ancestor that lived around 600 million years ago, called the urbilaterian. A bilaterian animal is one that has symmetrical left and right body halves. While it is still debated whether this species
Choroidal fissure ganglion cells in the sensory retina) do not lie in the groove that is the choroid fissure, they do extend through the portions of the optic stalk that form the walls of the fissure. These axons will form the optic nerve. The fissure is eventually sealed when the lips of the optic cup, as well as the edges of the groove in the optic stalk, fuse. Failure of this fissure to close results in coloboma iridis. Choroidal fissure The choroid is the middle, vascular coat of the eye which resides between the sclera and the retina. Early in development the