Muscles of the Upper Limb That Are Dissected in the Back Region
| Muscle | Origin | Insertion | Action | Innervation | Artery | Notes |
|---|---|---|---|---|---|---|
| latissimus dorsi | vertebral spines from T7 to the sacrum, posterior third of the iliac crest, lower 3 or 4 ribs, sometimes from the inferior angle of the scapula | floor of the intertubercular groove | extends the arm and rotates the arm medially | thoracodorsal nerve (C7,8) from the posterior cord of the brachial plexus | thoracodorsal a. | the inserting tendon twists so that fibers originating highest insert lowest |
| levator scapulae | transverse processes of C1-C4 vertebrae | medial border of the scapula from the superior angle to the spine | elevates the scapula | dorsal scapular nerve (C5); the upper part of the muscle receives branches of C3 & C4 | dorsal scapular a. | levator scapulae is named for its action |
| rhomboideus major | spines of vertebrae T2-T5 | medial border of the scapula inferior to the spine of the scapula | retracts, elevates and rotates the scapula inferiorly | dorsal scapular nerve (C5) | dorsal scapular a. | named for its shape |
| rhomboideus minor | inferior end of the ligamentum nuchae, spines of vertebrae C7 and T1 | medial border of the scapula at the root of the spine of the scapula | retracts, elevates and rotates the scapula inferiorly | dorsal scapular nerve (C5) | dorsal scapular a | named for its shape |
| serratus anterior | ribs 1-8 or 9 | medial border of the scapula on its costal (deep) surface | it draws the scapula forward; the inferior fibers rotate the scapula superiorly | long thoracic nerve (from ventral rami C5-C7) | lateral thoracic a. | a lesion of long thoracic nerve will cause winging of the scapula (i.e., the medial border of the scapula falls away from the posterior chest wall and looks like an angel's wing) |
| trapezius | medial third of the superior nuchal line, external occipital protuberance, ligamentum nuchae, spinous processes of vertebrae C7-T12 | lateral third of the clavicle, medial side of the acromion and the upper crest of the scapular spine, tubercle of the scapular spine | elevates and depresses the scapula (depending on which part of the muscle contracts); rotates the scapula superiorly; retracts scapula | motor: spinal accessory (XI), proprioception: C3-C4 | transverse cervical a. | named for its shape; trapezius is an example of a muscle that migrates during development from its level of origin (cervical) to its final position, pulling its nerve and artery along behind |
Muscles of the Back Region
| Muscle | Origin | Insertion | Action | Innervation | Artery | Notes |
|---|---|---|---|---|---|---|
| erector spinae | iliac crest, sacrum, transverse and spinous processes of vertebrae and supraspinal ligament | angles of the ribs, transverse and spinous processes of vertebrae, posterior aspect of the skull | extends and laterally bends the trunk, neck and head | segmentally innervated by dorsal primary rami of spinal nerves C1-S5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | the erector spinae m. is separated into 3 columns of muscle: iliocostalis laterally, longissimus in an intermediate position and spinalis medially; each of these columns has multiple named parts |
| iliocostalis | iliac crest and sacrum | angles of the ribs | extends and laterally bends the trunk and neck | dorsal primary rami of spinal nerves C4-S5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | the most lateral part of the erector spinae; it may be subdivided into lumborum, thoracis and cervicis portions |
| interspinales | upper border of spinous process | lower border of spinous process above | extend trunk and neck | dorsal primary rami of spinal nerves C1-L5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | these are small and fairly insignificant muscles |
| intertransversarii | upper border of transverse process | lower border of transverse process above | laterally bend trunk and neck | dorsal primary rami of spinal nerves C1-L5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | these are small and fairly insignificant muscles |
| longissimus | transverse process at inferior vertebral levels | transverse process at superior vertebral levels and mastoid process | extends and laterally bends the trunk, neck and head | dorsal primary rami of spinal nerves C1-S1 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | the intermediate part of the erector spinae;it may be subdivided into thoracis, cervicis and capitis portions |
| multifidus | sacrum, transverse processes of C3-L5 | spinous processes 2-4 vertebral levels superior to their origin | extend and laterally bend trunk and neck, rotate to opposite side | dorsal primary rami of spinal nerves C1-L5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | semispinalis, multifidus and rotatores make up the transversospinal muscle group |
| obliquus capitis inferior | spinous process of the axis | transverse process of atlas | rotates the head to the same side | suboccipital nerve (DPR of C1) | occipital a. | greater occipital nerve (DPR of C2) passes superiorly around the inferior margin of inferior oblique |
| obliquus capitis superior | transverse process of atlas | occipital bone above inferior nuchal line | extends the head, rotates the head to the same side | suboccipital nerve (DPR of C1) | occipital a. | the suboccipital triangle is formed by obliquus capitis superior and inferior and rectus capitis posterior major |
| rectus capitis posterior major | spinous process of axis | inferior nuchal line | extends the head, rotate to same side | suboccipital nerve (DPR of C1) | occipital a. | none |
| rectus capitis posterior minor | posterior tubercle of atlas | inferior nuchal line medially | extends the head | suboccipital nerve (DPR of C1) | occipital a. | rectus capitis posterior minor is deeper and inserts more medial than rectus capitis posterior major |
| rotatores | transverse processes | long rotatores: spines 2 vertebrae above origin; short rotatores: spines 1 vertebrae above origin | rotates the vertebral column to the opposite side | dorsal primary rami of spinal nerves C1-L5 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | semispinalis, multifidus and rotatores make up the transversospinal muscle group |
| semispinalis | transverse processes of C7-T12 | capitis: back of skull between nuchal lines; cervicis & thoracis: spines 4-6 vertebrae above origin | extends the trunk and laterally bends the trunk, rotates the trunk to the opposite side | dorsal primary rami of spinal nerves C1-T12 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | three parts are named based on their insertions: capitis, cervicis and thoracis; semispinalis, multifidus and rotatores make up the transversospinal muscle group |
| serratus posterior inferior | thoracolumbar fascia, spines of vertebrae T11-T12 and L1-L2 | ribs 9-12, lateral to the angles | pulls down lower ribs | branches of the ventral primary rami of spinal nerves T9-T12 | lowest posterior intercostal a., subcostal a., first two lumbar aa. | a respiratory muscle, it receives ventral ramus innervation; embryonically related to the intercostal muscles, not the deep back mm. |
| serratus posterior superior | ligamentum nuchae, spines of vertebrae C7 and T1-T3 | ribs 1-4, lateral to the angles | elevates the upper ribs | branches of the ventral primary rami of spinal nerves T1-T4 | posterior intercostal aa. 1-4 | a respiratory muscle, it receives ventral ramus innervation; embryonically related to the intercostal muscles, not the deep back mm. |
| spinalis | spinous processes at inferior vertebral levels | spinous processes at superior vertebral levels and base of the skull | extends and laterally bends trunk and neck | dorsal primary rami of spinal nerves C2-L3 | supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa. | most medial part of the erector spinae; may be subdivided into thoracis, cervicis and capitis portions |
| splenius | ligamentum nuchae and spines C7-T6 | capitis: mastoid process & superior nuchal line laterally; cervicis: posterior tubercles of C1-C3 vertebrae | extends and laterally bends neck and head; rotates head to same side | dorsal primary rami of spinal nerves C2-C6 | supplied segmentally by: deep cervical a., posterior intercostal aa. | splenius means bandage; it gets its name from its broad, flat shape |
| splenius capitis | ligamentum nuchae and spines of C7-T6 vertebrae | mastoid process and lateral end of the superior nuchal line | extends and laterally bends the neck and head, rotates head to the same side | dorsal primary rami of spinal nerves C2-C6 | supplied segmentally by: deep cervical a., posterior intercostal aa. | named for its shape: splenius means bandage and capitis refers to the insertion of this portion of the muscle |
| splenius cervicis | ligamentum nuchae and spines of C7-T6 vertebrae | posterior tubercles of the transverse processes of C1-C3 vertebrae | extends and laterally bends neck and head, rotates head to the same side | dorsal primary rami of spinal nerves C2-C6 | supplied segmentally by: deep cervical a., posterior intercostal aa. | named for its shape: splenius means bandage and cervicis refers to the insertion of this portion of the muscle |