Origin: Spinous process
Insertion: Spinous process
Nerve: Posterior rami of spinal nerves
Action: Extension, flexion and rotation of vertebral column.
The Interspinales are short muscular fasciculi, placed in pairs between the spinous processes of the contiguous vertebrae, one on either side of the interspinal ligament. In thecervical region they are most distinct, and consist of six pairs, the first being situated between the axis and third vertebra, and the last between the seventh cervical and the first thoracic. They are small narrow bundles, attached, above and below, to the apices of the spinous processes. In the thoracic region, they are found between the first and second vertebrae, and sometimes between the second and third, and between the eleventh and twelfth. In the lumbar region there are four pairs in the intervals between the five lumbar vertebrae. There is also occasionally one between the last thoracic and first lumbar, and one between the fifth lumbar and the sacrum.