neuroanatomy Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defi ...

, a gyrus (: gyri) is a ridge on the

cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. It is the largest site of Neuron, neural integration in the central nervous system, and plays ...

. It is generally surrounded by one or more sulci (depressions or furrows; : sulcus). Gyri and sulci create the folded appearance of the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

s and other

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

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 Gyrification is the process of forming the characteristic folds of the cerebral cortex. The peak of such a fold is called a ''gyrus'' (pl. ''gyri''), and its trough is called a ''Sulcus (neuroanatomy), sulcus'' (pl. ''sulci''). The neurons of the ...

during fetal and neonatal development. In

embryo An embryo ( ) is the initial stage of development for 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 sp ...

nic development, all

ian brains begin as smooth structures derived from the

neural tube In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, ...

. A

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, lissencephaly, and polymicrogyria are all the results of abnormal

cell migration Cell migration is a central process in the development and maintenance of multicellular organisms. Tissue formation during embryogenesis, embryonic development, wound healing and immune system, immune responses all require the orchestrated movemen ...

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 Epilepsy is a group of Non-communicable disease, non-communicable Neurological disorder, neurological disorders characterized by a tendency for recurrent, unprovoked Seizure, seizures. A seizure is a sudden burst of abnormal electrical activit ...

and mental dysfunctions. Pachygyria (meaning "thick" or "fat" gyri) is a congenital malformation of the cerebral hemisphere, resulting in unusually thick gyri in the

. 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 pregn ...

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 (: gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulcus (neuroanatomy), sulci (depressions or furrows; : sulcus). Gyri and sulci create the folded appearance of the brain in huma ...

and a thickening of the

. 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, ''lat''. gyrus frontalis superior *

Middle frontal gyrus The middle frontal gyrus makes up about one-third of the frontal lobe of the human brain. (A gyrus is one of the prominent "bumps" or "ridges" on the cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer la ...

, ''lat''. gyrus frontalis medius *

Inferior frontal gyrus The inferior frontal gyrus (IFG; also gyrus frontalis inferior) is the lowest positioned gyrus of the frontal gyri, of the frontal lobe, and is part of the prefrontal cortex. Its superior border is the inferior frontal sulcus (which divides it ...

, ''lat''. gyrus frontalis inferior with 3 parts: pars opercularis (

Brodmann area 44 Brodmann area 44, or BA44, is part of the frontal cortex in the human brain. Situated just anterior to premotor cortex ( BA6) and on the lateral surface, inferior to BA9. This area is also known as pars opercularis (of the inferior frontal gyr ...

) pars triangularis ( Brodmann area 45), and pars orbitalis (

orbital part of inferior frontal gyrus The orbital part of inferior frontal gyrus also known as the pars orbitalis is the orbital part of the inferior frontal gyrus. In humans, this region is bordered by the triangular part of the inferior frontal gyrus (pars triangularis) and, su ...

) *

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 l ...

, ''lat''. gyrus temporalis superior * Middle temporal gyrus, ''lat''. gyrus temporalis medius * Inferior temporal gyrus, ''lat''. gyrus temporalis inferior *

Fusiform gyrus The fusiform gyrus, also known as the ''lateral occipitotemporal gyrus'','' ''is part of the temporal lobe and occipital lobe in Brodmann area 37. The fusiform gyrus is located between the lingual gyrus and parahippocampal gyrus above, and ...

, ''lat''. gyrus occipitotemporalis lateralis * Parahippocampal gyrus, ''lat''. gyrus parahippocampalis * Transverse temporal gyrus * Lingual gyrus ''lat''. gyrus lingualis * Precentral gyrus, ''lat''. gyrus praecentralis * Postcentral gyrus, ''lat''. gyrus postcentralis * Supramarginal gyrus, ''lat''. gyrus supramarginalis * Angular gyrus, ''lat''. gyrus angularis * Cingulate gyrus ''lat''. gyrus cinguli * Fornicate gyrus

References

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

Structure

Development

Clinical significance

Notable gyri

See also

References