Longus Colli Muscle
There are a great number of muscles around the neck. They act to shield the deep structures, provide structural support to the cervical region (a region of the vertebral column that is quite unstable when compared to the thoracic and lumbar regions). The muscles of the neck also enable us to move our heads and shoulder girdle. There are various group of muscles in the neck. Longus colli is one of the anterior vertebral muscles. In this article we will discuss the gross and functional anatomy of this muscle. We will also discuss the clinical relevance of the structure, and provide a summary of key points at the end of the article. We will finally conclude with some review questions to test the reader’s understanding of the article content.
The longus colli derives its name from Latin for ‘long muscle of the neck.’ It acts as a flexor of the neck and head. It arises from the transverse processes of C5 to T3, and inserts onto the anterior arch of the Atlas. The muscle is located lying against the anterior surface of the vertebral column, and connects the atlas to the third thoracic vertebra. The muscle has narrow ends and a broad central section. There are three sections to the muscle, superior oblique, inferior oblique and a vertical intermediate section.
The superior oblique section originates from the anterior tubercles of the 3rd, 4th, and 5th cervical vertebral transverse processes. The muscle ascends in a gradually medial direction, to terminate on the anterior arch of the atlas. The inferior oblique section arises from the anterior surface of the first three thoracic vertebral bodies, and also ascends up, but this muscle has a gradually lateral inclination. The muscle terminates by inserting onto the anterior tubercles of the transverse processes of the 5th and 6th cervical vertebrae. The inferior oblique is the smallest section of the longus colli muscle. The vertical portion arises from the ventral surfaces of the bodies of the of the superior 3 thoracic and lower 3 cervical vertebrae. This muscle section inserts onto the anterior surface of the bodies of the 2nd to 4th cervical vertebrae.
Bilateral action of the muscle causes neck and head flexion, and unilateral action causes rotation of the head to the ipsilateral side. The lateral border of the longus colli muscle lies against the scalenus anterior muscle. The blood supply to the muscle comes from muscular branches of the vertebral, inferior thyroid and ascending pharyngeal arteries. The Longus colli muscle is innervated by the ventral rami of the 2nd to 4th cervical spinal nerves.
Carotid tubercle/Tubercle of Chassaignac
Where the lateral border of the longus colli meets the medial border of the scalenus anterior, a pyramidal space is formed. The first section of the subclavian artery forms the base of the pyramidal space, and the vertebral artery and cervical sympathetic trunk lie within the pyramidal space (against the lateral aspect of the longus colli muscle). The apex of this pyramidal space lies over the carotid tubercle. This tubercle is the anterior tubercle of the transverse process of the sixth cervical vertebra. The carotid artery can be identified lying anterior to this tubercle, and the phrenic nerve arises just above this tubercle.