Multifidus muscles

The musculi multifidi are continuous deep series muscle bundles coursing dorsocranially over several segments of the spine.

Origin: mamillary, transverse or articular processes

Insertion: spinous processes

Action: rotate vertebral column

Nerve: Medial branches of the rami dorsales in the lumbar, thoracic and cervical regions.

Different bundles may be described as:

• Multifidi laterales: lateral fascicles

• Multifidi mediales: medial fascicles

• Multifidi profundi: deep fascicles

In some species like dogs, multifidi may be described separately with each segment of the spine: 

Multifidus Lumborum

Origin: Articular processes of the sacrum, first caudal vertebra and from the mamillary processes of the seventh lumbar vertebrae to the twelfth thoracic vertebra.

Insertion: Laterally on the ends of the spinous processes of the sixth lumbar to the ninth thoracic vertebra.

Action: Fixes the vertebral column especially in bilateral action.

Nerve: Medial branches of the rami dorsales in the lumbar, thoracic and cervical regions.

Multifidus Thoracis

Origin: It arises by nine distinctly isolated portions on the mamillary and transverse processes of the eleventh to the third thoracic vertebra.

Insertion: Spinous processes of the eighth thoracic to the seventh cervical vertebra.

Action: Fixes the vertebral column especially in unilateral action.

Nerve: Medial branches of the rami dorsales in the lumbar, thoracic and cervical regions.

Multifidus cervicis:

Six incompletely separable individual covered by the semispinalis capitis, deep to the ventrolateral border of spinalis, semispinalis thoracis and semispinalis cervicis.

Origin: articular processes of cervical vertebrae

Insertion: spinous process of the axis