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Content: T-tubule - Wikipedia
T-tubule
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Invagination of the plasma membrane of a muscle cell that extends inward from the cell surface around each myofibril; the ends of T-tubules make contact with the sarcoplasmic reticulum membrane
T-tubule
Skeletal muscle, with T-tubule labelled in zoomed in image. T-tubule structure and relationship to the sarcoplasmic reticulumin skeletal muscle
Details
Part of
Cell membraneof Skeletal muscleand cardiac musclecells. Identifiers
Latin
tubulus transversus
TH
H2.00.05.2.01018, H2.00.05.2.02013  
Anatomical terminology
[edit on Wikidata]
T-tubules(transverse tubules) are extensions of the  cell membrane that penetrate into the centre of skeletaland cardiac musclecells. With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potentialinto the cell, and also play an important role in regulating cellular calcium concentration. Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell.[1] T-tubule structure may be affected by disease, potentially contributing to heart failureand arrhythmias. Although these structures were first seen in 1897, research into T-tubule biology is ongoing. Contents
1Structure
1.1Regulators
2Function
2.1Excitation-contraction coupling
2.2Calcium control
2.3Detubulation
3History
4Clinical significance
5See also
6References
Structure[edit]
T-tubules are tubules formed from the same phospholipid bilayeras the surface membrane or sarcolemmaof skeletal or cardiac muscle cells.[1] They connect directly with the sarcolemma at one end before travelling deep within the cell, forming a network of tubules with sections running both perpendicular (transverse) to and parallel (axially) to the sarcolemma.[1] Due to this complex orientation, some refer to T-tubules as the transverse-axial tubular system.[2] The inside or lumen of the T-tubule is open at the cell surface, meaning that the T-tubule is filled with fluid containing the same constituents as the solution that surrounds the cell (the extracellular fluid). Rather than being just a passive connecting tube, the membrane that forms T-tubules is highly active, being studded with proteins including L-type calcium channels, sodium-calcium exchangers, calcium ATPases and Beta adrenoceptors. [ 1]
T-tubules are found in both atrialand ventricularcardiac muscle cells (cardiomyocytes), in which they develop in the first few weeks of life.[3] They are found in ventricular muscle cells in most species, and in atrial muscle cells from large mammals.[4] In cardiac muscle cells, T-tubules are between 20 and 450 nanometers in diameter and are usually located in regions called Z-discswhere the actin filaments anchor within the cell.[1] T-tubules within the heart are closely associated with the intracellular calcium store known as the sarcoplasmic reticulumin specific regions referred to as terminal cisternae.