The longus colli is a muscle of the anterior neck. With fibers running almost parallel to the spinal column, it stretches from the atlas bone just beneath the base of the skull all the way to the upper thoracic spine. This muscle is considered to have three distinct sections: the above or superior oblique portion, the intermediate or vertical portion, and the lower or inferior oblique portion. Together, these segments of the longus colli act to flex, or bend forward, the head and neck.
As this muscle has multiple portions, it has multiple points of origin and insertion on the bones to which it attaches. The superior oblique portion, which is the uppermost on the neck, originates on the transverse processes or sideways bony projections of C3-C5 in the cervical spine, of which there are seven vertebrae. Its fibers run upward and inward to attach to the anterior arch of the atlas, also known as C1. The anterior arch is the front portion of the ring that is the body of the atlas bone.
Below, the superior oblique portion of the longus colli is the vertical portion, which as its name suggests features fibers running vertically rather than obliquely. This portion originates on the anterior surface of the vertebral bodies of T1-T3, the three topmost thoracic vertebrae, and C5-C7, the three bottommost cervical vertebrae. Its fibers ascend parallel to the cervical spine to insert along the anterior surfaces of C2, also known as the axis, through C4.
The lower section of the longus colli muscle is known as the inferior oblique portion, whose fibers angle upward and outward rather than upward and inward like those of the superior oblique portion. It originates on the anterior surface of T1 and T2 and sometimes T3, and from there it attaches above on the transverse processes of C5 and C6 in the cervical spine. Essentially it is identical to the superior oblique portion, but inverted, with the two portions meeting at the transverse process of C5.
Though it has three distinct sections, the longus colli functions as a unit to flex the head and neck. This means it pulls the front of the cervical vertebrae forward and downward, which in turn pulls the chin downward. The longus colli is also the muscle that tends to be injured in accidents causing whiplash. When a person is hit abruptly from behind, as in having one’s car rear-ended, he is first thrown forward, and then the subsequent recoil throws the head back and hyperextends the muscles on the front of the neck, resulting in a whiplash injury.