precentral gyrus

The precentral gyrus, also known as the primary motor cortex, is a very important structure involved in executing voluntary motor movements.

Gross anatomy

The precentral gyrus is a diagonally oriented cerebral convolution situated in the posterior portion of the frontal lobe. It is located immediately anterior to the central sulcus (fissure of Rolando), running parallel to it .

In the precentral gyrus, large neurons known as Betz cells send efferent axons that terminate on the contralateral motor cranial and spinal nuclei. The functional organization of the precentral gyrus is such that clusters of Betz cells are somatotopically represented by an inverted homunculus. Therefore, head and face regions are innervated by the inferior portion of the precentral gyrus. Conversely, the lower limbs are innervated by the superior portion .

Relations

Anterior to the precentral gyrus, separated by the precentral sulcus, lie a set of areas composing the lateral premotor cortex and the supplemental motor area. Posteriorly, separated by the central sulcus, lies the primary somatosensory cortex.

Medially and inferiorly, it is bound by the cingulate gyrus. Laterally and inferiorly, it is bound by the Sylvian fissure .

The precentral gyrus is continuous with the postcentral gyrus on both the medial and superolateral aspects of each hemisphere. Medially, this occurs via the paracentral lobule, and superolaterally this connection is via the subcentral gyrus, which may be hidden within the operculum.