Vertebrae
Cervical Vertebrae
Features of typical cervical vertebrae C3-C6 and of C7
The body is small, wide and oval in shape – it does not have to carry as much weight as vertebrae lower down the column. The upper surface of the body is concave transversely while the lower surface is concave along the anteroposterior axis.
The raised superior edges of the body form the uncinate processes, which articulate with the adjacent vertebra. These are an extra area of articulation and only found in animals that can rotate their head, rather than just sway their heads like cattle.
The articular facets are oval shaped and flat.
Superior facets
The superior facets are directed backwards, upwards and medially
Inferior processes
The inferior processes are directed in the opposite direction
This does not allow much rotation of one vertebra on the other, but does allow flexion, extension and lateral flexion.
Are pierced by the foramen transversarium. Each transverse process has an anterior/costal tubercle and a posterior tubercle. The scalene muscles attach to these tubercles
The vertebral artery passes through this, one either side, before passing through the foramen magnum to supply the brain.
The anterior tubercle is thought to be a degenerated rib and sometimes can be quite large. It may exist as a separate bone, forming a cervical rib. This occurs most commonly on C7.
Are short and bifid on C3-C6
The spinous process of C7 is non-bifid and is the largest and most superior that can be felt through the skin. It is sometimes called the vertebra prominens for that reason.
Provides the attachment for the ligamentum nuchae. The ligamentum nuchae is the tough ligament that runs from the external occipital protuberance of the skull to the spinous process of C7. It limits flexion of the cervical spine
Cervical C1 Atlas
The atlas is the first cervical vertebra. It is a ring of bone and is very different from a ‘typical’ vertebra, with specific anatomical features shown below.
Features of atlas C1
It has no spinous process
It has no body. Its body is thought to have become fused with that of the C2 vertebra to form the odontoid peg, which sits within the bony ring of the atlas and articulates with it
It has an anterior and a posterior arch
The arches provide attachment for the deep neck muscles, ligaments and membranes.
The odontoid peg articulates with the anterior arch of the atlas by means of oval-shaped articular cartilages, one on the posterior surface of the anterior arch of the atlas and the other on the anterior surface of the odontoid peg
It has two lateral masses.
These are the most bony parts of the C1 vertebra, formed by the transverse process and the facet joint on each side
Each lateral mass has an upper and a lower facet. The superior facets on the upper surfaces of the lateral masses form cups for the corresponding condyles of the occipital bone with which it articulates
They are shaped to allow the skull to rock backwards and forwards, so that the head can nod. The inferior facets articulate with the axis (C2 vertebra)
This stretches across the ring of the atlas and divides the vertebral foramen into two unequal parts.
The smaller, anterior part receives the odontoid process of the axis; the posterior part transmits the spinal cord and its membranes
Transverse Atlantal Ligament
The transverse atlantal ligament stretches across the ring of the atlas and divides the vertebral foramen into two unequal parts. The smaller, anterior part receives the odontoid process of the axis; the posterior part transmits the spinal cord and its membranes.
Cervical C2 Axis
Is usually bifid
Are thick and strong
The odontoid process or peg, also known as the dens, is a bony projection rising from the upper surface of the body of the axis. It sits within the ring of C1, anterior to the transverse ligament, and articulates with the posterior surface of the anterior arch of the atlas.
The superior facets are flat in the horizontal plane and lie either side of the base of the odontoid peg. They articulate with the inferior facets on the lateral masses of the atlas. This arrangement of the facet joints allows rotational movement of the head.
The transverse processes are small. In common with the other cervical vertebrae, the transverse processes are also perforated by foramina transversaria.
The atlas is stabilized by strong ligaments that run from C2 to the base of the skull.
This stretches across the ring of the atlas and divides the vertebral foramen into two unequal parts.
The smaller, anterior part receives the odontoid process of the axis; the posterior part transmits the spinal cord and its membranes