Thoracic OIA

Erector Spinae (Iliocostalis) Origin

Angles of ribs 3-12; Iliac crest; Sacrum

Erector Spinae (Iliocostalis) Insertion

Posterior tubercles of C4-C6; Ribs 1-12; Transverse process of L1-L4

Erector Spinae (Iliocostalis) Action

Extends spine; Laterally flexes spine

Erector Spinae (Longissimus) Origin

Transverse process of C4-T5; Spinous process of L1-L5; Posterior sacrum; Iliac tuberosity

Erector Spinae (Longissimus) Insertion

Mastoid process; Transverse processes of C2-L5; Ribs 5-12

Erector Spinae (Longissimus) Action

Extends head; Extends spine; Laterally flexes spine

Erector Spinae (Spinalis) Origin

Transverse process C7-T2; Transverse process of T11-L2

Erector Spinae (Spinalis) Insertion

Spinous process C2-C4; Spinous process T2-T8

Erector Spinae (Spinalis) Action

Extends thoracic and cervical spine; Laterally flexes thoracic and cervical spine

Semispinalis Origin

Superior articulating facets C4-C7; Transverse processes T1-T10

Semispinalis Insertion

Occipital bone between nuchal lines; Spinous processes C2-T4

Semispinalis Action

Extends head; Extends cervical spine

Splenius Capitis Origin

Spinous process of C7-T4

Splenius Capitis Insertion

Mastoid process of temporal bone; Lateral superior nuchal line

Splenius Capitis Action

Extends head, Laterally flexes head, Ipsilaterally rotates head

Splenius Cervicis (Colli) Origin

Spinous processes of T3-T6

Splenius Cervicis (Colli) Insertion

Transverse processes of C1-C3

Splenius Cervicis (Colli) Action

Extend cervical spine; Laterally flexes cervical spine; Ipsilaterally rotates cervical spine

External Intercostals Origin

Lower borders of ribs (1)

External Intercostals Insertion

Superior border of subjacent ribs (1)

External Intercostals Action

Elevates ribs during inspiration

Internal Intercostals Origin

Costal grooves and inferior borders of ribs

Internal Intercostals Insertion

Superior borders of subjacent ribs (2)

Internal Intercostals Action

Depresses ribs during force expiration (2)

Innermost Intercostals Origin

Lower borders of ribs (3)

Innermost Intercostals Insertion

Superior borders of subjacent ribs (3)

Innermost Intercostals Action (3)

Depresses ribs during force expiration

Serratus Posterior Superior Origin

Spinous processes of C7-T3

Serratus Posterior Superior Insertion

Superior aspects of ribs 2-5

Serratus Posterior Superior Action

Elevates ribs