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 (pl. 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. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consistin ...

. It is generally surrounded by one or more

sulci Sulci or Sulki (in Greek , Steph. B., Ptol.; , Strabo; , Paus.), was one of the most considerable cities of ancient Sardinia, situated in the southwest corner of the island, on a small island, now called Isola di Sant'Antioco, which is, how ...

(depressions or furrows; sg. ''sulcus''). Gyri and sulci create the folded appearance of the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a ve ...

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

s 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 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'' (pl. ''sulci''). The neurons of the cerebral cortex re ...

during fetal and neonatal development. In embryonic development, all mammalian 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 fold become elevated, ...

. A

without surface convolutions is lissencephalic, meaning 'smooth-brained'. As development continues, gyri and

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 Lissencephaly (, meaning "smooth brain") is a set of rare brain disorders whereby the whole or parts of the surface of the brain appear smooth. It is caused by defective neuronal migration during the 12th to 24th weeks of gestation resulting in ...

, and

polymicrogyria Polymicrogyria (PMG) is a condition that affects the development of the human brain by multiple small gyri ( microgyri) creating excessive folding of the brain leading to an abnormally thick cortex. This abnormality can affect either one region o ...

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 embryonic development, wound healing and immune responses all require the orchestrated movement of cells in particular dire ...

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 neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrica ...

and mental dysfunctions.

(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 Neuronal migration disorder (NMD) refers to a heterogenous group of disorders that, it is supposed, share the same etiopathological mechanism: a variable degree of disruption in the migration of neuroblast In vertebrates, a neuroblast or primitive ...

; most commonly relating to lissencephaly.

Lissencephaly Lissencephaly (, meaning "smooth brain") is a set of rare brain disorders whereby the whole or parts of the surface of the brain appear smooth. It is caused by defective neuronal migration during the 12th to 24th weeks of gestation resulting in ...

(''smooth brain'') is a rare congenital brain malformation caused by defective neuronal migration during the 12th to 24th weeks of fetal gestation resulting in a lack of development of gyri and sulci.

Polymicrogyria Polymicrogyria (PMG) is a condition that affects the development of the human brain by multiple small gyri ( microgyri) creating excessive folding of the brain leading to an abnormally thick cortex. This abnormality can affect either one region o ...

(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 m ...

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.

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 surface of the human brain.) The middle frontal gyrus, like the inferior frontal gyrus an ...

, ''lat''. gyrus frontalis medius *

Inferior frontal gyrus The inferior frontal gyrus (IFG), (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 f ...

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

Brodmann area 44 Brodmann area 44, or BA44, is part of the frontal Front may refer to: Arts, entertainment, and media Films * ''The Front'' (1943 film), a 1943 Soviet drama film * ''The Front'', 1976 film Music *The Front (band), an American rock band sign ...

) pars triangularis (

Brodmann area 45 Brodmann area 45 (BA45), is part of the frontal cortex in the human brain. It is situated on the lateral surface, inferior to BA9 and adjacent to BA46. This area in humans occupies the triangular part of inferior frontal gyrus (H) and, surround ...

), 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, surr ...

) * Superior temporal gyrus, ''lat''. gyrus temporalis superior *

Middle temporal gyrus Middle temporal gyrus is a gyrus in the brain on the temporal lobe. It is located between the superior temporal gyrus and inferior temporal gyrus. It corresponds largely to Brodmann area 21. The middle temporal gyrus is bounded by: * the superi ...

, ''lat''. gyrus temporalis medius *

Inferior temporal gyrus The inferior temporal gyrus is one of three gyri of the temporal lobe and is located below the middle temporal gyrus, connected behind with the inferior occipital gyrus; it also extends around the infero-lateral border on to the inferior surface ...

, ''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 th ...

, ''lat''. gyrus occipitotemporalis lateralis *

Parahippocampal gyrus The parahippocampal gyrus (or hippocampal gyrus') is a grey matter cortical region of the brain that surrounds the hippocampus and is part of the limbic system. The region plays an important role in memory encoding and retrieval. It has been in ...

, ''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 The lingual gyrus, also known as the ''medial'' occipitotemporal gyrus, is a brain structure that is linked to processing vision, especially related to letters. It is thought to also play a role in analysis of logical conditions (i.e., logical ord ...

''lat''. gyrus lingualis *

Precentral gyrus The precentral gyrus is a prominent gyrus on the surface of the posterior frontal lobe of the brain. It is the site of the primary motor cortex that in humans is cytoarchitecturally defined as Brodmann area 4. Structure The precentral gyrus l ...

, ''lat''. gyrus praecentralis *

Postcentral gyrus In neuroanatomy, the postcentral gyrus is a prominent gyrus in the lateral parietal lobe of the human brain. It is the location of the primary somatosensory cortex, the main sensory receptive area for the sense of touch. Like other sensory areas, ...

, ''lat''. gyrus postcentralis *

Supramarginal gyrus The supramarginal gyrus is a portion of the parietal lobe. This area of the brain is also known as Brodmann area 40 based on the brain map created by Korbinian Brodmann to define the structures in the cerebral cortex. It is probably involved wi ...

, ''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 The cingulate cortex is a part of the brain situated in the medial aspect of the cerebral cortex. The cingulate cortex includes the entire cingulate gyrus, which lies immediately above the corpus callosum, and the continuation of this in the ...

''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