True or False? Smooth muscle cells contain T-tubules.

Smooth muscle cells do not contain T-tubules like skeletal muscle and cardiac muscle cells do. T-tubules are invaginations of the sarcolemma that help to conduct action potentials into the interior of the muscle fiber, facilitating the coordinated contraction of muscle. In skeletal and cardiac muscle, these structures play a crucial role in excitation-contraction coupling.

Smooth muscle operates differently. Instead of T-tubules, smooth muscle cells have a more diffuse network of calcium channels and rely primarily on calcium release from the sarcoplasmic reticulum and extracellular fluid. This difference in structure aligns with the functional requirements of smooth muscle, which is involved in involuntary movements such as digestion and blood vessel regulation, rather than the rapid contractions seen in skeletal and cardiac muscle.

Given this information, the statement that smooth muscle cells contain T-tubules is incorrect, as they lack these structures entirely. Therefore, the true answer is that smooth muscle cells do not possess T-tubules, making the correct response "False."