Corpus: Longissimus muscle

The longissimus muscle is part of the sacrospinal system within the autochthonous back muscles.

The longissimus muscle is traditionally divided into three parts:

• Longissimus thoracis
• Longissimus cervicis
• Longissimus capitis

Some authors also identify a fourth part, the longissimus lumborum, which can alternatively be considered part of the iliocostalis muscle. This highlights the general difficulty in clearly differentiating muscle entities within the autochthonous back musculature.

3.1. Origin

The longissimus thoracis muscle originates from the dorsal surface of the sacral bone, the spinous processes of the lumbar vertebrae, and the transverse processes of the lower thoracic vertebrae. The longissimus cervicis muscle originates from the transverse processes of the 1st to 6th thoracic vertebrae, while the longissimus capitis muscle originates from the transverse processes of the 3rd cervical vertebra to the 3rd thoracic vertebra.

3.2. Attachment

The longissimus thoracis muscle inserts on the transverse processes of the thoracic and lumbar vertebrae and attaches to the 2nd to 12th ribs, between the angle of the rib and the rib tubercle. The longissimus cervicis muscle attaches to the posterior tubercles of the transverse processes of the 2nd to 7th cervical vertebrae. The longissimus capitis muscle attaches to the mastoid process of the temporal bone.

The longissimus muscle is innervated segmentally by the posterior branches of the spinal nerves.

The function of the longissimus muscle varies according to its different parts:

• The longissimus thoracis extends (dorsiflexes) and laterally flexes the thoracic and lumbar spine and supports expiration.
• The longissimus cervicis extends (dorsiflexes) and laterally flexes the cervical and thoracic spine.
• The longissimus capitis extends (dorsiflexes), rotates, and laterally inclines the head and cervical spine.