T-tubule

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

Etymology

The term "T-tubule" comes from the tubules' unique T-shape. The "T" stands for "transverse," which refers to their orientation in the muscle cell relative to the cell's surface.

Structure

T-tubules are formed from the sarcolemma, the cell membrane of a muscle cell. They are oriented perpendicularly to the cell surface, penetrating deep into the cell. The T-tubules are closely associated with the sarcoplasmic reticulum, a specialized form of endoplasmic reticulum, through structures called triads in skeletal muscle and dyads in cardiac muscle.

Function

The primary role of T-tubules is to allow for the rapid transmission of the action potential into the cell, which triggers calcium release from the sarcoplasmic reticulum. This calcium release is what initiates muscle contraction.

Clinical significance

Alterations in T-tubule structure or function can lead to muscle weakness and disease. For example, in heart failure, the organization of T-tubules can become disrupted, leading to impaired calcium handling and reduced muscle contraction.

See also

• Sarcomere
• Myofibril
• Muscle contraction

T-tubule

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