Cervical Vertebrae 1-7
C7 - 7th Cervical Vertabra
The 7th cervical (C7) vertebra is the largest and most inferior vertebra in the neck region. Unlike the other cervical vertebrae, the C7 has a large spinous process that protrudes posteriorly toward the skin at the back of the neck. This spinous process can be easily seen and felt at the base of the neck, making it a prominent landmark of the skeleton and giving the C7 the name vertebra prominens. The C7 is located in the spinal column inferior to the 6th cervical (C6) vertebra and superior to the first thoracic (T1) vertebra. As the transitional vertebra between the cervical and thoracic regions, the C7 has some features of both the cervical and thoracic vertebrae. Like the C3 through C6 vertebrae, C7 has a thicker area of bone called the body, located anterior to the vertebral foramen. The body of C7 supports the collective weight of the head and neck. Facets lateral to the C7's body allow the C7 to form joints with the C6 vertebra above it and the T1 below it. Fibrocartilaginous disks above and below the C7's body provide cushioning. The facets and disks surrounding the body provide both stability and flexibility to the neck. Posterior to the body is a thin ring of bone known as the vertebral arch. The vertebral arch surrounds the hollow vertebral foramen and provides muscle attachment sites to the C7 vertebra. Delicate tissues, including the spinal cord and nerves, pass through the vertebral foramen and are protected by the vertebral arch. Extending from both lateral sides of the vertebral arch are the transverse processes and their tiny, hollow transverse foramina. Each transverse foramen provides a conduit for nerves and the vertebral arteries and veins that supply blood to tissues of the head and neck. Several bony processes extend from the vertebral arch and provide important muscle attachment sites for the muscles of the neck. On both lateral sides of C7, the transverse processes provide insertion points for the erector spinae muscles that extend and flex the neck. The spinous process extends from the posterior of the vertebral arch to provide connection points for the muscles that extend the neck, including the trapezius and spinalis muscles. Unlike the notched spinous processes of the C3-C6 vertebrae, the vertebra prominens resembles the T1 vertebra with a spinous process that is large, straight, and flattened at the end. The end of the nuchal ligament, which supports the muscles of the neck and connects the occipital bone of the skull to the C7 vertebra, attaches at the tip of the spinous process.
C1 Atlas - 1st Cervical Vertabra
The C1 vertebra, known as the atlas vertebra, is the first or uppermost of the thirty-three (33) vertebrae of the spinal column and of the cervical vertebrae. The first and second cervical vertebrae are distinct from the other true vertebrae or movable vertebrae below them. As the superior of the seven (7) cervical vertebrae, the C1 is granted the nickname of the atlas vertebra in its role, together with the C2 axis vertebra, of supporting the skull where the head attaches to the neck, just as the god Atlas upheld the world. The cranium's occipital condyles are seated and articulate on the C1 vertebra's lateral masses for vertical articulation of the head (nodding). As with the other cervical vertebrae, the C1 vertebra is among the smallest of the true vertebrae, occupying the neck and lying above the thoracic vertebrae. The C1, uniquely, lacks a ventral body or centrum, as it is fused with that of the C2 vertebra at its own odontoid peg together with the odontoid process or dens of the C2 axis vertebra. Only an anterior arch, a thin stretch of bone, crosses the spinal column where the centrum would exist in another vertebra. However, its transverse processes are quite large. Two oblique transverse foramen permit the passage of nerves, vertebral artery, and the vertebral vein away from the spinal cord - which passes through a large vertebral foramen, protecting the brain stem - and out to the body.
C2 Axis - 2nd Cervical Vertabra
The C2 vertebra, known as the axis vertebra or the epistropheus, is the second-uppermost of the vertebrae making up the backbone and of the seven (7) cervical vertebrae at the top of the spine. Its nickname, the axis vertebra, derives from its role in allowing the head to rotate from its support atop the C1 vertebra where the skull attaches to the neck. As with the C1, the C2 vertebra is different from the other true vertebrae or moveable vertebrae below them. The ventral body or centrum of the C2 is actually contiguous with the C1 vertebra, which lacks a separate ventral body; but it is this fusion in part that gives the C1-C2 joint a wide range of lateral motion (providing most of the lateral motion of the head and neck). This fusion gives the C2 vertebra a third name, the vertebra dentata, for the tooth-like odontoid process or dens-a protuberance that rises from the back of the centrum and fuses with the odontoid peg of the atlas vertebra. The vertebral foramen of the axis vertebra is large enough to protect the last of the brain stem yet slightly smaller than that of the C1, but two oblique transverse foramen likewise allow the passage of nerves, the vertebral artery, and the vertebral vein from the spinal cord out to the body.
C3 - 3rd Cervical Vertebra
The C3 vertebra is one of the seven (7) cervical vertebrae, sitting just below the C2 axis vertebra and the C1 atlas vertebra within the neck. After the C1 and C2 vertebrae, the C3-C6 vertebrae are often grouped together as very similar, and as with the other movable vertebrae they are characterized by two primary parts: a vertebral arch that protects the spinal cord and the centrum or ventral body that provides strength, protection, and mobility to the spinal column and thus to the body. The centrum is concave on its upper surface and convex below, with cartilaginous intervertebral discs providing cushioning between these surfaces and those of the respective inferior and superior articular facets of the adjacent vertebrae, simultaneously aiding the articulation between itself and the C2 vertebra above and the C4 below. Two transverse foramina interrupt the structure of the vertebral arch to allow for the passage of the vertebral artery and vein as well as the sympathetic nerves servicing that region of the neck and body to pass through from the protected spinal column. A bifid (notched) spinous process extends beyond the vertebral arch.
C4 - 4th Cervical Vertabra
The C4 vertebra is the fourth of the seven (7) cervical vertebrae that make up the spinal cord in the area of the neck. After the C1 and C2 vertebrae, the C3-C6 vertebrae are often grouped together as similar to one another in form and function. The C4 vertebra, like the other cervical vertebrae, is relatively small in relation to the other vertebrae but with a large vertebral foramen for the passage of the nerves of the spinal cord. Two transverse foramina pass through the vertebral arch, permitting the sympathetic nerves, vertebral vein, and vertebral artery to pass from the spinal column and out to the body. The vertebral body or centrum and the superior and inferior articular facets work in conjunction with the C3 vertebra above and C5 below to allow for smooth articulation of the spine, cushioned by intervertebral discs. Posterior to the vertebral arch, a notched (bifid) spinous process extends for connection of the spine to muscles and ligaments.
C5 - 5th Cervical Vertabra
The C5 vertebra is the fifth of seven (7) cervical vertebrae at the top of the spinal column. After the C1 and C2 vertebrae, the C3-C6 vertebrae are often grouped together since they are much alike in form and function. Like the others, the C5 is relatively smaller and more flexible than the other true or movable vertebrae. Its triangular vertebral foramen within the vertebral arch is smaller than that of the vertebrae above it but larger than the spinal foramina of the vertebrae below it. Two transverse foramina pass through the bone's vertebral arch to allow for the passage of the sympathetic nerves, vertebral vein, and vertebral artery away from the spinal cord and out to the body. Anterior to the vertebral arch, the vertebral body or centrum is concave on top and convex below where it meets with the respective articular joints of the C4 vertebra above it and C6 below to allow for the movement of the neck. Intervertebral discs between the centrums of each bone (as well as between the respective superior articular facet and inferior articular facet of each spinal bone) protect and support the spinal column while enabling smooth movement of the backbone.
C6 - 6th Cervical Vertabra
The C6 vertebra is the sixth cervical vertebra of the spine. It is found in the base of the neck between the C5 and the last cervical vertebra, C7. The C6 vertebra plays an important role in supporting and protecting the structures of the head and neck as well as anchoring the muscles that move and support the neck. The C6 vertebra is located in the inferior end of the neck just above the thorax. It is the second most inferior cervical vertebra as well as the second largest; only the C7 vertebra is larger and more inferior. The anterior region of the C6 vertebra is made of a short cylinder of bone known as the centrum or vertebral body. The centrum forms a column continuous with the neighboring vertebrae, connected by the intervertebral disks. The intervertebral disks are thin masses of tough fibrocartilage with a soft, gel-like center. Each disk acts as a shock absorber for the spine while helping to hold the vertebral column in alignment. The transverse processes extend laterally from the centrum and contain small holes known as the transverse foramina. The vertebral arteries and veins pass through the foramina, along with some nervous tissue. A bony ring known as the vertebral arch extends laterally and posteriorly from the centrum to surround the spinal cord and provide attachment points for the muscles of the neck. The pedicles of the vertebral arch extend from the left and right sides of the centrum posteriorly and laterally before widening into the superior and inferior articular processes. The articular processes form planar synovial joints with the neighboring vertebrae, allowing the neck to rotate and providing greater mobility to the head. The superior articular process is slightly convex to join with the concave inferior process of the C5 vertebra. Conversely, the inferior articular process is concave to match up with the convex superior articular process of the C7 vertebra. Posterior to the articular processes, the vertebral arch continues posteriorly and medially as the laminae, which meet at the body's midline to complete the arch. From this union, the bone continues posteriorly for a short distance as the thin, flat spinous process that can be felt through the skin on the back of the neck. The C6 vertebra plays a vital role in supporting and protecting the tissues of the neck. The spinal cord passes through the vertebral foramen and is protected by the bony tissue of the C6 vertebra. Likewise, the vertebral arteries and veins pass through and are protected by the transverse foramina. Several muscle groups attach to the C6 vertebra to move and support the neck. Rotatores muscles connect to the transverse process to rotate the neck, while the longissimus muscle pulls on the transverse process to laterally flex the neck. The trapezius muscle of the back has one of its origins on the spinous process of the C6 vertebra. Also connected to the spinous process is the thin multifidus muscle, which helps to support the neck and maintain the body's posture.
