The interspinales are short, paired muscles of the back lying in the deepest layer, extending between spinous processes of two adjacent vertebrae. These muscles extend through the entire spine, however, they are most developed in the cervical and lumbar regions.

All interspinales receive innervation via the dorsal rami of spinal nerves. The main function of the interspinales is to stabilize the spine during movement and maintain normal posture. They also aid other deep back muscles in extending the spine.

Interspinales cervicis

Origin and insertion: they originate from the superior aspect of spinous processes of cervical vertebrae C2 to C7 and insert into the inferior aspect of the adjacent vertebrae C1 to C6, respectively. Located one on either side of the interspinous ligament.

Action: aid in extension of the cervical spine; most importantly, these muscles participate in stabilizing the cervical spine and maintaining a normal posture of the body.

Innervation: dorsal rami of spinal nerves.

Blood supply: vertebral artery, deep cervical artery, occipital artery, as well as the transverse cervical artery.

Interspinales thoracis

These muscles are usually underdeveloped or even absent, with only some portions having distinct muscle fascicles. There are usually three pairs of interspinales thoracis present.

Origin and insertion: the three developed interspinales thoracis muscles arise from the superior aspect of the spinous processes of the second (T2), eleventh (T11) and twelfth thoracic vertebra (T12), but this can be variable. Each attaches to the inferior aspect of the spinous processes of the vertebra one level above (T1, T10, and T11, accordingly).

Action: these muscles are usually underdeveloped, but they may aid in extension of the thoracic spine.

Innervation: dorsal rami of spinal nerves.

Blood supply: superior intercostal artery, posterior intercostal arteries, and subcostal artery.

Interspinales lumborum

Origin and insertion: muscle fibers originate from the superior aspect of spinous processes of second to fifth lumbar vertebrae (L2 - L5) and insert into the inferior aspect of the spinous processes of the adjacent vertebrae (L1 - L4, accordingly).

Action: participate in stabilizing the lumbar spine and providing a normal body posture, and they may also aid in extension of the lumbar part of the spine.

Innervation: dorsal rami of spinal nerves.

Blood supply: mainly, lumbar arteries.

Unlock with Premium

Interspinales muscles