The levatores costarum (or levator costae) muscles are paired muscles of the posterior thorax. They number twelve on each side and attach to the transverse processes of C7 to T11 vertebrae and the ribs below, helping to elevate the ribs during respiration.
- origin: transverse processes of C7 to T11 vertebrae
- insertion: rib immediately below
- innervation: dorsal rami of C8 to T11 spinal nerves
- action: elevate ribs
Each fan-shaped levator costarum muscle attaches near the tip of a transverse process of C7 to T11 vertebrae and passes inferolaterally to attach to the superior border of the rib immediately below, between the tubercle and angle of the rib 1-3. They are superficial to the external intercostal muscles.
The four most inferior muscles may divide into two fascicles 3:
- levator costarum brevis: which inserts onto the rib immediately below the vertebra of origin
- levator costarum longus: which inserts onto the rib two levels below the vertebra of origin
The levatores costarum muscles are the only thoracic muscles which are supplied by the dorsal rami of the C8 to T11 spinal nerves.
Each muscle helps to elevate the ribs, however, they are thought to play a relatively unimportant role during inspiration.