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a tubular invagination of the sarcolemma of skeletal or cardiac muscle fibers that surrounds myofibrils as the intermediate element of the triad in skeletal muscle and the diad in cardiac muscle; involved in transmitting the action potential from the sarcolemma to the interior of the myofibril.
Synonym(s): T tubule
The transverse tubule that passes from the sarcolemma across a myofibril of striated muscle; it is the intermediate tubule of the triad.
see transverse tubules.