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The Atlas (the an initial cervical vertebra - C1) different from the other cervical vertebrae in that it has no body or spinous process. That is made up of 2 bony arcs with 2 bony masses laterally. It articulates through the Occiput over and C2 (the Axis) below.

Anterior Arch

The anterior arch forms around one-fifth the the ring.

Its anterior surface is convex, and presents in ~ its center the anterior tubercle because that the attachments of the Longus colli muscles and the anterior longitudinal ligament.

Posteriorly that is concave, and marked by a smooth, oval or circular page (fovea dentis), because that articulation with the odontoid process (dens) of the axis.

The upper and lower borders respectively give attachment come the anterior atlantooccipital membrane and the anterior atlantoaxial ligament; the former connects it through the occipital bone above, and also the latter with the axis below.

Posterior Arch

The posterior arch forms about two-fifths of the one of the ring.

It ends behind in the posterior tubercle, which is the rudiment that a spinous process and offers origin come the Recti capitis posteriores minores and also the ligamentum nuchae. The diminutive dimension of this process prevents any kind of interference v the movements between the atlas and also the skull.

The posterior part of the arch presents above and behind a rounded edge for the attachment of the posterior atlantooccipital membrane, while immediately behind each exceptional articular procedure is a groove (sulcus arteriae vertebralis), occasionally converted into a foramen by a delicate bony spiculum which arches backward native the posterior end of the superior articular process. This groove to represent the premium vertebral notch, and also serves for the transmission of the vertebral artery, which, ~ ascending v the foramen in the transverse process, winds around the lateral fixed in a direction backward and medially; it additionally transmits the suboccipital nerve (first spinal nerve). In a typical anatomic variant the vertebral artery passes with an arcuate foramen. On the under surface of the posterior arch, behind the articular facets, are two shallow grooves, the inferior vertebral notches. The lower border provides attachment come the posterior atlantoaxial ligament, i beg your pardon connects it through the axis.

Lateral Masses

The lateral masses are the most bulky and also solid parts of the atlas, in bespeak to support the weight of the head. Every carries 2 articular facets, a superior and an inferior.

The remarkable facets space of big size, oval, concave and also directed upward, medially, and a little backward, each creating a cup for the matching condyle of the occipital bone and allowing nodding activity of the head.

The inferior articular facets space circular in form, planarization or slightly convex and directed downward and medially, articulating with the axis, and permitting the rotatory activities of the head.

The medial element of each mass has a tubercle for the attachement of the transverse ligament.

Vertebral Foramen

Just below the medial margin of each exceptional facet is a little tubercle, because that the attachments of the transverse atlantal ligament which stretches throughout the ring of the atlas and also divides the vertebral foramen into two unlike parts: the anterior or smaller receiving the odontoid procedure of the axis the posterior transmitting the spinal cord (medulla spinalis) and also its membrane This part of the vertebral canal is of substantial size, much greater than is forced for the house of the spinal cord.

Transverse Processes

The transverse processes are large; they job laterally and downward from the lateral masses, and also serve because that the attachment of muscles which help in rotating the head. They room long, and also their anterior and also posterior tubercles are fused right into one mass; the foramen transversarium is directed from below, upward and also backward.


Superiorly the atlas articulates with the occiput to form the Atlanto-occipital share which permits the head to nod up and down top top the vertebral column.

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Inferiorly the atlas articulates v the dens which acts together a pivot that allows the atlas and also attached head to turn on the axis. This is the Atlanto-axial joint.