Gyrus

In neuroanatomy, a gyrus (pl. gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; sg. sulcus). Gyri and sulci create the folded appearance of the brain in humans and other mammals.

Structure

The gyri are part of a system of folds and ridges that create a larger surface area for the human brain and other mammalian brains. Because the brain is confined to the skull, brain size is limited. Ridges and depressions create folds allowing a larger cortical surface area, and greater cognitive function, to exist in the confines of a smaller cranium.

Development

The human brain undergoes gyrification during fetal and neonatal development. In embryonic development, all mammalian brains begin as smooth structures derived from the neural tube. A cerebral cortex without surface convolutions is lissencephalic, meaning 'smooth-brained'. As development continues, gyri and sulci begin to take shape on the fetal brain, with deepening indentations and ridges developing on the surface of the cortex.