A concentrated layer (~50-100 nm thick) of actin filaments
that lie longitudinally and roughly parallel to each other just beneath
the plasma membrane. These so called “cortical filaments” have been
described in numerous cell types [1]. Migrating fibroblasts grown in 2D
tissue culture have more cortical filaments on the
dorsal (upper) surface than the ventral (lower) surface and they are concentrated towards the trailing edges [1] (see Figure below, panel B).