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origin: the transverse process of the 6th to 10 Thoracic vertebrae;
insertion: the spinous process of the 1st to 4th thoracic and 6th-7th cervical vertebrae;
action: extends the spine and rotates it toward the opposite side;
nerve supply: posterior rami of the thoracic nerves,   T1  to T6;
synergists: Longissimus Thoracis, Iliocostalis thoracis, Spinalis Thoracis