Interspinales lumborum muscles

At a glance

English

Interspinales lumborum muscles

Latin (TA2)

Musculi interspinales lumborum

System

Muscle

Region

Back

Side

Paired, left and right

About the interspinales lumborum muscles

The interspinales are tiny muscles that link the spinous process of one vertebra to the one directly below it. They belong to the deepest layer of the back muscles, the segmental group, and are found mainly in the neck and the lower back, where the spinous processes are broad and move apart in flexion.

In the lumbar region they are well developed. A pair, one on either side of the interspinous ligament, occupies each gap between adjacent lumbar spines. An extra pair may be present between T12 and L1, and another between L5 and the sacrum. Each muscle is a short, flat block of fibres running straight up and down from the upper edge of one spine to the lower edge of the spine above.

Their pull is very short, so their contribution to extending the spine is small. More importantly they steady each lumbar segment during movement and prevent excess separation of the spines when the back bends forward. Like other small segmental muscles they contain many muscle spindles and probably act largely as sensors of the position and movement of each vertebra.

They are supplied by the medial branches of the dorsal rami of the lumbar spinal nerves, and blood comes from the dorsal branches of the lumbar arteries. They lie deep to multifidus and are divided in surgical approaches to the lumbar spine through the midline.

Attachments, action and supply

Origin

Upper border of a lumbar spinous process.

Insertion

Lower border of the spinous process immediately above.

Action

Help to extend and steady the lumbar spine segment by segment; signal vertebral position.

Nerve supply

Medial branches of the dorsal rami of the lumbar spinal nerves.

Blood supply

Dorsal branches of the lumbar arteries.