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Anatomy, Head and Neck, Cervical Vertebrae
Joshua T. Kaiser; Vamsi Reddy; Julian G. Lugo-Pico.Author Information
The spine, or vertebral column, is a segmental collection of 33 bones and associated soft tissues that consist of the subcranial portion of the axial skeleton. The subdivides into 5 regions based upon curvature and also morphology: the cervical, thoracic, and lumbar spine, the sacrum, and also the coccyx. There room seven, twelve, and five articulating vertebrae in the cervical, thoracic, and also lumbar spine. While somewhat comparable in regards to bone morphology, this three regions variably balance spinal rigidity v flexibility and also movement and also articulate in a certain fashion that contributes to the in its entirety S-shaped curvature of the spine. Meanwhile, the sacrum and also the coccyx space two to adjust of fused vertebrae at the caudal element of the spine the convey no motion. 5 fused vertebrae typically kind the sacrum, through four creating the coccyx.<1>
The cervical spine, comprised of seven cervical vertebrae referred to as C1 come C7, is divided into two major segments: the craniocervical junction (CCJ) and also the subaxial spine. The CCJ consists of the occiput and the 2 most cephalad cervical vertebrae well-known as the atlas (C1) and also the axis (C2). The subaxial spine contains the 5 most caudal cervical vertebrae (C3-C5). Together a whole, the cervical spine is responsible for sustaining the weight of the cranium and allowing motion the the head and also neck.
Structure and Function
The usual vertebrae have hallmark anatomic structures that space conserved throughout the cervical, thoracic, and lumbar regions. Generally, each vertebra is made up of a ventral vertebral body made up of mostly trabecular cancellous and a denser, mainly cortical dorsal vertebral arch. The vertebral body is the key site of intervertebral articulation and load-bearing. Every vertebral body is attached to that cranial and also caudal counterparts by an intervertebral disk. The dorsal arch generally consists that a pair the pedicles arising from the dorsal vertebral body, which hold together dorsally by a pair of level laminae. The two laminae sign up with at the midline producing a dorsal projection called the spinous process. The pedicles, laminae, and dorsum of the vertebral body type the vertebral foramen, a complete osseous ring that encloses the spinal cord. The main role is to protect the spinal cord and also its associated vascular structures. Additionally, the transverse processes and the superior and also inferior articular processes are current near the junction the the pedicles and the laminae. In the cervical spine, the costal procedure becomes the anterior component of the transverse process that encloses the vertebral artery foramen.<2>
Unique attributes of the Cervical Spine
Despite displaying most usual vertebral hallmarks, a significant amount that anatomical variation exist within the cervical spine. The main function of the cervical spine is to support and also promote the motion of the head and also neck. Large vertebral bodies room not vital considering the relatively small weight-bearing load at this level. Thus, one increased selection of motion takes priority over vertebral size and rigidity. However, the added motion and also flexibility may carry an enhanced risk for injury the the spinal cord and its associated neurovascular structures. All 7 cervical vertebrae have actually a transverse foramen within your transverse processes, whereby a pair that vertebral arteries take trip cranially v the vertebrae starting at C6 before coursing medially over the arch that C1 in the direction of the foramen magnum. The spinous procedures of the C2 come C6 vertebrae space bifid, C1 has actually a posterior tubercle instead of a spinous process, and C7 has a lot larger and also singular spinous process, known as the vertebra prominens, which is similar to those in the thoracic vertebrae.<3>
The upper Cervical Spine – The Axis (C1) and also the Atlas (C2)
The top cervical region of the cervical spine includes C1 and also C2, i beg your pardon are more commonly referred to as the atlas and the axis, respectively. The main duty of the atlas is to support and also cradle the base of the occiput in ~ the atlanto-occipital articulation. together such, there are many features unique to the atlas not mutual with the remainder of the spine. many notably, the atlas lacks a vertebral body and instead creates a huge ring-shaped fusion of anterior and also posterior arcs that enables C1 come accommodate the spinal cord as it exits the foramen magnum. The atlas has pronounced concave and medially encountering articular facets i m sorry accommodate the convex occipital condyles. This morphology help the joint contribute approximately fifty percent of flexion-extension the the neck yet limit lateral displacement the the occiput. These joints receive more stabilization from strong soft-tissue ligaments that promote tight follow to the occiput.<2><4>
The axis, or C2, likewise possesses unique anatomical features. Vice versa, the atlas is responsible for accommodating the occiput, the axis is the major weight-bearing bone the the upper cervical region. The hallmark feature is that is odontoid process, or dens, a bony projection prolonging cranially indigenous the vertebral body. It evolved from the body of the atlas and serves together the major attachment suggest for the soft tissues that stabilize the atlantoaxial junction. In contrast to the atlanto-occipital joint, the atlantoaxial junction is responsible for about fifty percent the the rotational activity of the cervical spine. The junction has three articulations: a midline atlanto-odontoid (or atlanto-dental) joint and also a pair of atlantoaxial side joints. The atlanto-odontoid joint permits the anterior arch the the atlas come pivot top top the odontoid process. The lateral side joints indicate the articulation of the atlas’ worse facets and also the premium facets the the axis; these joints are reasonably shallow to enable for significant motion.<2><3><4><5>
The Subaxial Cervical Spine – C3 to C7
All 5 vertebrae in this an ar share nearly identical morphological and also functional features, and compared to the upper cervical spine, re-superstructure most attributes with the common vertebral anatomy. Distinct to these, all 5 vertebrae possess uncinate processes, which space bony prominences ~ above the lateral edges of the vertebral body the articulate in ~ Luschka joints come confer additional stability and also prevent vertebral listhesis.
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There also exist part minor functions of C7 that distinguish it from the remainder of the subaxial region. The transverse foramen the C7 is smaller sized in diameter than the remainder of the an ar and commonly does not home the vertebral arteries. Instead, the vertebral arteries overcome anteriorly to the transverse procedures of C7 before proceeding cranially v the transverse foramina that C6. Additionally, C7 is considered a transitional vertebra, and as such, has actually a spinous process and inferior facets the resemble thoracic vertebrae. The vertebra likewise has a somewhat bigger vertebral body.<6>