T tubule

T-tubule (or transverse tubule), is a deep invagination of the plasma membrane found in the cardiac myocyte and skeletal striated muscle cells. These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell.

Structure

T-tubules are formed from the sarcolemma, the cell membrane of a muscle cell, and they dive into the cell's interior. They are named for their transverse orientation to the myofibrils. The T-tubules play a crucial role in excitation-contraction coupling by allowing the depolarization of the action potential to rapidly reach the interior of the cell.

Function

The primary role of the T-tubule is to allow the rapid transmission of the action potential into the cell, which triggers calcium release from the sarcoplasmic reticulum. This process is essential for muscle contraction. In cardiac muscle cells, the T-tubules are wider and less regular than in skeletal muscle cells, and they play a crucial role in ensuring that the heart beats in a coordinated manner.

Clinical significance

Alterations in T-tubule structure and function have been associated with diseases such as heart failure and certain muscular dystrophies. In heart failure, for example, the T-tubules can become disorganized, leading to a decrease in the efficiency of calcium release and muscle contraction.

See also

• Sarcolemma
• Sarcoplasmic reticulum
• Excitation-contraction coupling