Longissimus

The longissimus is the muscle lateral to the semispinalis. It is the longest subdivision of the erector spinae that extends forward into the transverse processes of the posterior cervical vertebrae.

Structure

Longissimus thoracis

The longissimus thoracis is the intermediate and largest of the continuations of the erector spinae.

In the lumbar region, where it is as yet blended with the iliocostalis lumborum, some of its fibers are attached to the whole length of the posterior surfaces of the transverse processes and the accessory processes of the lumbar vertebræ, and to the anterior layer of the lumbodorsal fascia.

In the thoracic region, it is inserted, by rounded tendons, into the tips of the transverse processes of all the thoracic vertebræ, and by fleshy processes into the lower nine or ten ribs between their tubercles and angles.

Longissimus cervicis

The longissimus cervicis (transversalis cervicis), situated medial to the longissimus thoracis, arises by long, thin tendons from the summits of the transverse processes of thoracic vertebræ 1-5, and is inserted by similar tendons into the posterior tubercles of the transverse processes of cervical vertebrae 2-6.