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Spinalis
- Most medial
- Origin: Thoracolumbar aponeurosis, SPs of upper lumbar and lower thoracic vertebrae, Ligamentum nuchae
- Insertion: Ascending SPs except C1
- Bilateral action: Extends the head and spine
- Unilateral actions: ipsilateral lateral flexion of neck and trunk (bending side to side)
- Nonropy
- Deep to trap, lats, and part of longissimus
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Longissimus
- Dense, feels ropy
- Origin: Thoracolumbar aponeurosis; TVPs thoracic region
- Insertion: Ascending TVPs, mastoid process
- Bilateral action: extends head and spine (primary)
- Unilateral actions: ipsilateral lateral flexion of neck and trunk; ipsilateral rotation of head and neck
- Nonropy
- Deep to traps and lats
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Iliocostalis
- Very flat and broad
- Origin: Thoracolumbar aponeurosis; iliac crest
- Insertion: Ascending rib to rib; loweral cervical TVPs (ends by medial border of the scap)
- Bilateral action: extends the spine
- Unilateral actions: Ipsilateral lateral flexion of neck and trunk (where it crosses C7); ipsilateral rotation of neck
- Nonropy
- Deep to trap and lat
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