Betz cells (also known as
pyramidal cells of Betz) 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 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 are
upper motor neurons that send their
axons down to the
spinal cord via the
corticospinal tract, where in
humans they
synapse directly with
anterior horn cells, 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 branches/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.