text: A<unk>  (or transverse<unk> , is a deep invagination of the plasma membrane found in skeletal and cardiac muscle cells.  These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell.
option_0: T-tubule
option_1: Intermediate filament
option_2: Cytoskeleton
option_3: Reticular fiber
option_4: Tight junction
option_5: Hemidesmosome
option_6: Association fiber
option_7: Climbing fiber