Skeletal muscles

 The function of T-TUBULES
is to conduct impulses from the
surface of the cell
(SARCOLEMMA) down into
the cell and, specifically, to
another structure in the cell
called the SARCOPLASMIC
RETICULUM.
 As they open to the exterior,
the extracellular fluid runs
through their lumen.

,
,L TUBULES – SARCOPLASMIC
RETICULUM
Extend throughout the sarcoplasm.
Together called sarcoplasmic Reticulum.
Runs in long axes of the muscle fiber and hence called longitudinal
tubules or “L tubules”.
Form a closed tubular system around each myofibril.
They do not open to exterior like T tubules.
It cones ponds to the endoplasmic reticulum of other cells regular
intervals, throughout the length of the myofibrils, the L tubules
delate to form a pair of lateral sacs called terminal cisternae.
Each pair of terminal cisternal is in close contact with T tubule.
(The T tubule along with cisterae on either side is called the triad of
skeletal muscle).

, FUNCTIONS OF T TUBULES
Responsible for rapid transmission of impulse in the form of action
potential to the myofibrils.