T-tubule
INVAGINATION OF THE PLASMA MEMBRANE OF A MUSCLE CELL THAT EXTENDS INWARD FROM THE CELL SURFACE AROUND EACH MYOFIBRIL; THE ENDS OF T-TUBULES MAKE CONTACT WITH THE SARCOPLASMIC RETICULUM MEMBRANE
T tubules; T-tubules; Transverse tubules; T tubule; Transverse tubular system; Transverse tubule; T-Tubule; A-I junction
T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells. With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration.