Betz cells are giant pyramidal cells (neurons) located within the fifth layer of the grey matter in the primary motor cortex. They are named after Ukrainian scientist Vladimir Alekseyevich Betz, who described them in his work published in 1874. These neurons are the largest in the central nervous system, sometimes reaching 100 μm in diameter. Betz cells send their axons down to the spinal cord via the corticospinal tract where in humans they synapse directly with anterior horncells, which in turn synapse directly with their target muscles. While Betz cells have one apical dendrite typical of pyramidal neurons, they have more primary dendritic shafts, which can branch out at almost any point from the soma (cell body). These perisomatic (around the cell body) and basal dendrites project into all cortical layers, but most of their horizontal arbors populate layers V and VI, some reaching down into the white matter. According to one study, Betz cells represent about 10% of the total pyramidal cell population in layer Vb of the human primary motor cortex.
^Betz W. (1874) Anatomischer Nachweis zweier Gehirncentra. Centralblatt für die medizinischen Wissenschaften. 12:578-580, 595-599.
^Purves, Dale, George J. Augustine, David Fitzpatrick, William C. Hall, Anthony-Samuel LaMantia, James O. McNamara, and Leonard E. White (2008). Neuroscience. 4th ed. Sinauer Associates. pp. 432–4. ISBN978-0-87893-697-7.
^Braak, H; Braak, E (1976). "The pyramidal cells of Betz within the cingulate and precentral gigantopyramidal field in the human brain. A Golgi and pigmentarchitectonic study.". Cell and tissue research172 (1): 103–19. PMID991201.
^Meyer, G (1987). "Forms and spatial arrangement of neurons in the primary motor cortex of man.". The Journal of comparative neurology262 (3): 402–28. doi:10.1002/cne.902620306. PMID3655019.
^Rivara, CB; Sherwood, CC; Bouras, C; Hof, PR (2003). "Stereologic characterization and spatial distribution patterns of Betz cells in the human primary motor cortex.". The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology270 (2): 137–51. doi:10.1002/ar.a.10015. PMID12524689.