Longus colli muscle

Origin and insertion

Longus colli runs the entire length of the neck; between the atlas (first cervical vertebra) and T3 (third thoracic vertebra). It is narrow at its superior and inferior ends and has a broad central section. The muscle consists of three parts which are attached to the vertebral column via tendinous slips:

• Superior oblique part - originates from the anterior tubercles of transverse processes of the third, fourth and fifth cervical vertebrae (C3-C5). The muscle ascends gradually in a superomedial direction to terminate on the anterior tubercle of anterior arch of atlas (C1).
• Vertical intermediate part - arises from the anterior surfaces of bodies of lower three cervical and superior three thoracic vertebrae (C5-T3). This muscle section inserts onto the anterior surface of bodies of second, third and fourth cervical vertebrae (C2-C4).
• Inferior oblique part - is the smallest section of the longus colli muscle. It arises from the anterior surfaces of bodies of first three thoracic vertebrae (T1-T3). It ascends superolaterally, terminating onto the anterior tubercles of transverse processes of fifth and sixth cervical vertebrae (C5-C6).

Test yourself on the anterior muscles of the anterior neck with this interactive quiz.

Relations

Longus colli, and all prevertebral muscles, are located deep to the prevertebral fascia, which is a layer of the deep cervical fascia of the neck. The muscle sits in the groove formed by the junction of the transverse process with the vertebral body, posterior to the retropharyngeal space. Therefore, the esophagus, trachea, thyroid gland and muscles of the hyoid (supra-, infra-) all sit anterior to it. Longus colli is bordered medially by the cervical plexus, brachial plexus and subclavian artery.

The medial border of scalenus anterior muscle lies close to the lateral border of longus colli. Here, a pyramidal space is formed, with the first section of the subclavian artery forming its base. The thoracic duct, cervical sympathetic trunk and first part of the vertebral artery (V1) all lie within this pyramidal space, passing between the longus colli and scalenus anterior muscles. The cervicothoracic ganglion also lies lateral to the longus colli muscle at the level of the seventh cervical vertebra.

Posterior to longus colli, one can find the carotid artery (including the carotid sheath) and phrenic nerve. These lie anterosuperiorly to the tubercle of transverse process of the sixth cervical vertebra. In addition, the inferior thyroid artery follows a medial course inferior to this tubercle and then descends along the longus colli muscle towards the thyroid gland.

The origins of the vertical and inferior parts of longus colli represent the deepest structures of the superior mediastinum.

Blood supply

The blood supply to longus colli comes from the muscular branches of the following three arteries:

• Vertebral artery
• Inferior thyroid artery
• Ascending pharyngeal artery

Innervation

Longus colli muscle is innervated by the anterior rami of the second to sixth cervical spinal nerves (C2-C6).

Functions

Bilateral contraction of the muscle causes flexion of the neck (i.e. forward movement). Unilateral contraction, especially of the inferior oblique part, also results in weak lateral flexion (ipsilaterally) and contralateral rotation of the neck. However, some sources doubt the unilateral action of longus colli due to its almost mid-sagittal position. These actions have important stabilizing functions for the vertebral column, aligning the head and neck for upright posture. For further details about these movements and the muscles of the neck, take a look below: