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

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

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 The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

Development

The human brain undergoes gyrification during fetal and neonatal development. In

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

nic development, all

ian 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.

Clinical significance

Changes in the structure of gyri in the cerebral cortex are associated with various diseases and disorders.

Pachygyria Pachygyria (from the Greek "pachy" meaning "thick" or "fat" gyri) is a congenital malformation of the cerebral hemisphere. It results in unusually thick convolutions of the cerebral cortex. Typically, children have developmental delay and seizures, ...

, lissencephaly, and polymicrogyria are all the results of abnormal cell migration associated with a disorganized cellular architecture, failure to form six layers of cortical neurons (a four-layer cortex is common), and functional problems. The abnormal formation is commonly associated with epilepsy and mental dysfunctions.

(meaning "thick" or "fat" gyri) is a congenital malformation of the cerebral hemisphere, resulting in unusually thick gyri in the cerebral cortex. Pachygyria is used to describe brain characteristics in association with several neuronal migration disorders; most commonly relating to lissencephaly. Lissencephaly (''smooth brain'') is a rare congenital brain malformation caused by defective neuronal migration during the 12th to 24th weeks of fetal

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...

resulting in a lack of development of gyri and sulci. Polymicrogyria (meaning "many small gyri") is a developmental malformation of the human brain characterized by excessive folding of the

gyri 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 ma ...

and a thickening of the cerebral cortex. It may be generalized, affecting the whole surface of the cerebral cortex or may be focal, affecting only parts of the surface. Polymicrogyria may be caused by mutations within several genes, including ion channels.

Notable gyri

Superior frontal gyrus In neuroanatomy, the superior frontal gyrus (SFG, also marginal gyrus) is a gyrus – a ridge on the brain's cerebral cortex – which makes up about one third of the frontal lobe. It is bounded laterally by the superior frontal sulcus. The su ...

, ''lat''. gyrus frontalis superior * Middle frontal gyrus, ''lat''. gyrus frontalis medius * Inferior frontal gyrus, ''lat''. gyrus frontalis inferior with 3 parts: pars opercularis ( Brodmann area 44) pars triangularis ( Brodmann area 45), and pars orbitalis ( orbital part of inferior frontal gyrus) *

Superior temporal gyrus The superior temporal gyrus (STG) is one of three (sometimes two) gyri in the temporal lobe of the human brain, which is located laterally to the head, situated somewhat above the external ear. The superior temporal gyrus is bounded by: * the lat ...

, ''lat''. gyrus temporalis superior * Middle temporal gyrus, ''lat''. gyrus temporalis medius * Inferior temporal gyrus, ''lat''. gyrus temporalis inferior * Fusiform gyrus, ''lat''. gyrus occipitotemporalis lateralis * Parahippocampal gyrus, ''lat''. gyrus parahippocampalis *

Transverse temporal gyrus The transverse temporal gyri, also called Heschl's gyri () or Heschl's convolutions, are gyri found in the area of primary auditory cortex buried within the lateral sulcus of the human brain, occupying Brodmann areas 41 and 42. Transverse tempora ...

* Lingual gyrus ''lat''. gyrus lingualis * Precentral gyrus, ''lat''. gyrus praecentralis * Postcentral gyrus, ''lat''. gyrus postcentralis * Supramarginal gyrus, ''lat''. gyrus supramarginalis *

Angular gyrus The angular gyrus is a region of the brain lying mainly in the posteroinferior region of the parietal lobe, occupying the posterior part of the inferior parietal lobule. It represents the Brodmann area 39. Its significance is in transferring vis ...

, ''lat''. gyrus angularis * Cingulate gyrus ''lat''. gyrus cinguli *

Fornicate gyrus The limbic lobe is an arc-shaped region of cortex on the medial surface of each cerebral hemisphere of the mammalian brain, consisting of parts of the frontal, parietal and temporal lobes. The term is ambiguous, with some authors including the p ...

References

{{DEFAULTSORT:Gyrus (Neuroanatomy) * Cerebrum Neuroanatomy sv:Hjärnbark#Gyrus och sulcus

Structure

Development

Clinical significance

Notable gyri

See also

References