Is the Klein's bottle a good analogy to the relation between T-tubule and sarcolemma? I am not quite seeing how the T-tubule and sarcolemma is connected. It says that the T-tubule is an "invagination" of the sarcolemma, which is sarcolemma folded from the inside to form a T-tubule Can someone verify whether the following picture is a good presentation of this relationship? !enter image description here

If we're looking at diagrams for the t-tubule with respect to the sarcolemma, we see the two are actually fused:

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The function therein is to allow depolarization to penetrate the interior of the cell quickly. The surface isn't transected anywhere, it simply folds inward. You can visualize this by sort of pushing a hole through some putty with a finger, and making a hole to the other side. Really no need to upvote me here, just easier to paste images in answers.