Transverse tubules are the membranous channel that extends inward from the muscle cell, these are the actually the addition or extensions of the cell membrane that invade into the center of muscles cells except smooth muscles.
The role of the transverse tubules is to generating the stimulus or signals from the sarcolemma to down in the cell. Sarcolemma are the surface of the cells in muscles.
The texture of an igneous rock is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals.In addition to texture, igneous rocks may are classified according to their chemical composition.