Levatores costarum muscles

Origin and insertion

There are 12 separate muscle bundles that make up levatores costarum. Each originates from the transverse processes of one vertebra and passes obliquely to insert into the rib one level below. More specifically, the muscle bundle arises from the tip of the transverse processes of the associated vertebra (C7-T11). It then passes obliquely in an inferolateral direction to insert into the external aspect of the superior border of the rib, between the costal angle and tubercle of rib. The muscles are triangular in shape, with the apex pointing toward the origin and fanning out to form its base at the insertion.

The upper eight muscles (on each side) travel as single muscular bands from origin to insertion. In contrast, the lower four muscles split into two fasciculi called longi and breves (levatores costarum longi, levatores costarum breves). The short (breve) fascicle passes from the muscles’ origin to attach into the rib located immediately below, while the longer (longi) fascicle descends further to attach onto the rib located 2 levels below.

Relations 

Levatores costarum is lateral to the rotatores thoracis muscle group and medial to the external intercostal muscles. It is also located deep to semispinalis cervicis and thoracis muscles.

Innervation

Levatores costarum is innervated by the lateral branches of the posterior rami of spinal nerves (C8 – T11).

Blood supply

The dorsal branch of the posterior intercostal artery brings oxygenated blood to the levatores costarum muscles. The posterior intercostal artery is a direct branch of the thoracic aorta and travels along the lower border of each rib.

Functions

There are two major functions of levatores costarum. The first is to elevate the ribs and the second is to rotate and laterally flex the vertebra. Although it is able to elevate the ribs, there is some dispute about whether or not that levatores costarum plays an active role during inspiration.