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Interspinales

The interspinales (Latin: musculi 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. In the thoracic region, they are underdeveloped or often completely absent.

The primary 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

The interspinales cervicis (Latin: musculi interspinales cervicis) are paired muscles lying deep in the back of the neck, extending between spinous processes of two contiguous cervical vertebrae.

Origin and insertion

The interspinales cervicis 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. These muscles are located on either side of the interspinous ligament.

Action

The action aided by the interspinales cervicis is extension of the cervical spine. Most importantly, these muscles participate in stabilizing the cervical spine and maintaining a healthy body posture.

Innervation

The dorsal rami of spinal nerves innervate the interspinales cervicis.

Blood supply

The arterial blood supply to the interspinales cervicis is provided by the vertebral arterydeep cervical arteryoccipital artery, as well as the transverse cervical artery.

 

Interspinales thoracis

The interspinales thoracis (Latin: musculi interspinales thoracis) are deep muscles of the thoracic region of the back, extending between spinous processes of two adjacent thoracic vertebrae. These muscles are usually underdeveloped or even absent, with only some portions having distinct muscle fascicles. There are typically three pairs of interspinales thoracis present.

Origin and insertion

The three 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 the extension of the thoracic spine.

Innervation

The dorsal rami of spinal nerves innervate the interspinales thoracis.

Blood supply

These muscles are supplied by the superior intercostal arteryposterior intercostal arteries, and subcostal artery.

 

Interspinales lumborum

The interspinales lumborum (Latin: musculi interspinales lumborum) are a group of four paired muscles located deep in the lumbar part of the back.

Origin and insertion

The fibers of the interspinales lumborum 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

The interspinales lumborum participates in stabilizing the lumbar spine movements and providing a normal body posture, and they also aid in the extension of the lumbar spine.

Innervation

The dorsal rami of spinal nerves innervate the interspinales lumborum.

Blood supply

The arterial blood supply to the interspinales lumborum is provided mainly by the lumbar arteries.