The C3 Vertebra

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The C3, or third cervical vertebra, is one of the seven cervical vertebrae of the neck. It plays several vital roles in the neck, including supporting the spinal cord, several muscles, and the vertebral blood vessels. The C3 is the most superior cervical vertebra to have the standard cervical vertebra shape.

Anatomy

The C3 vertebra is a bone of the cervical spine found in the neck around the chin and hyoid bone. It’s third vertebra in the spinal column, inferior to the axis (C2 vertebra) and superior to the C4 vertebra.

The C3 vertebra is the first bone of the spinal column to feature the standard vertebral shape, unlike the C1 and C2 vertebrae that have unique shapes. On its anterior end, it has a large column of bone known as the vertebral body or centrum that makes up around half of its mass. The vertebral body is much wider than it is deep, slightly concave on its superior and inferior surfaces with a slight lip around the edge of the superior surface. Soft, cartilaginous intervertebral discs above and below the vertebral body connect to the vertebral bodies of the neighboring C2 and C4 vertebrae, producing a flexible spinal column.

Two pairs of bony projections arise from both lateral sides of the vertebral body and give rise to the vertebral arch, a bony ring posterior to the vertebral body. The transverse processes extend laterally from the vertebral body forming the anterior tubercle, turn 45 degrees posteriorly to form the posterior tubercle, and turn another 45 degrees posteriorly to meet the pedicles. Just posterior to the origin of the transverse processes, the pedicles extend obliquely posterior and lateral from the vertebral body to join the distal end of the transverse processes. These processes produce a small, heart-shaped hollow cavity on each side of the vertebral body known as the transverse foramen.

Posterior to the ends of the transverse processes and pedicles on each side is a small column that forms the superior and inferior articular processes. The superior articular process protrudes toward the inferior articular process of the C2 vertebra and forms a planar synovial joint. On the inferior end, the inferior articular process descends to meet the superior articular process of the C4 vertebra and forms a planar synovial joint. Both planar joints form on an oblique angle so that the anterior edge of the joint is superior relative to the posterior end.

A pair of bony processes called the lamina extend obliquely posterior and medial from the articular processes. Each lamina is triangular in cross section, with a narrow superior edge and a wide base on the inferior edge. The laminae meet at the body’s midline directly posterior to the vertebra body to complete the vertebral arch. Extending posteriorly from the union of the laminae is a forked bony projection known as the spinous process.

Physiology

The C3 vertebra plays several vital roles in the neck. As part of the spinal column, it supports the soft tissues of the neck and the weight of the head. It protects the delicate spinal cord that passes through the vertebral foramen and the nerves, vertebral arteries, and vertebral veins that pass through the transverse foramina. The intervertebral discs connecting C3 to its neighboring vertebrae act as shock absorbers in the spinal column to stabilize the body and prevent the collision of bones due to forces acting on the body, including the pull of gravity.

Many muscles form their origins or insertions on the transverse and spinous processes of the C3 vertebra to move various parts of the body. Several of these muscles — including the rotatores, semispinalis cervicis, intertransversarii, and splenius cervicis muscles — work together to extend the neck when working in pairs and laterally flex or rotate the neck when only one side contracts. The trapezius and levator scapulae muscles arise from the C3 to elevate the scapulae and shrug the shoulders. Another group of muscles, the anterior and middle scalenes, begin on the transverse processes of the C3 and elevate the rib cage during deep breathing.