Z Line Ultrastructure
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In longitudinal section, an actin filament on one side of the Z line lies between two actin filaments on the opposite side of the Z line. This arrangement indicates that the actin filaments per se do not pass through the Z line.
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The actin filaments are believed to terminate at the Z line. Ultra-thin filaments, called Z filaments, constitute the material of the Z line and they connect with actin filaments on either side of it.
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Near the Z line, each actin filament connects to four Z filaments that pass obliquely through the Z line.
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Each of the four Z filaments then connects with an actin filament in the adjacent sarcomere. This structural arrangement of the Z line shows each actin filament of one sarcomere oriented in the centre of four actin filaments from the next sarcomere.
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In longitudinal sections, this offset (or oblique) arrangement of the Z filaments results in the characteristic zigzag pattern of the Z line and explains why an actin filament on one side of the Z line appears to lie between two actin filaments of the apposing sarcomere.
![Z-FILAMENTS Z-FILAMENTS](http://14.139.56.154:82/file.php/161/Images/Z-FILAMENTS-1.jpg)
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Last modified: Friday, 23 December 2011, 11:25 AM