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Anatomy, Head and also 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 comprise the subcranial portion of the axial skeleton. That subdivides into 5 regions based on curvature and morphology: the cervical, thoracic, and lumbar spine, the sacrum, and the coccyx. There are seven, twelve, and also five articulating vertebrae in the cervical, thoracic, and also lumbar spine. If somewhat comparable in regards to bone morphology, these three areas variably balance spinal rigidity through flexibility and movement and also articulate in a specific fashion the contributes come the as whole S-shaped curvature that the spine. Meanwhile, the sacrum and the coccyx are two sets of fused vertebrae in ~ the caudal facet of the spine the convey no motion. Five fused vertebrae typically form the sacrum, v four forming the coccyx.<1>
The cervical spine, made up of 7 cervical vertebrae referred to as C1 to C7, is divided into two significant segments: the craniocervical junction (CCJ) and also the subaxial spine. The CCJ has the occiput and the two most cephalad cervical vertebrae well-known as the atlas (C1) and the axis (C2). The subaxial spine consists of the 5 most caudal cervical vertebrae (C3-C5). As a whole, the cervical spine is responsible for sustaining the weight of the cranium and enabling motion of the head and also neck.
Structure and also Function
The common vertebrae have hallmark anatomic structures that space conserved throughout the cervical, thoracic, and also lumbar regions. Generally, each vertebra is comprised of a ventral vertebral body consisted of of mostly trabecular cancellous and also a denser, largely cortical dorsal vertebral arch. The vertebral human body is the main site that intervertebral articulation and load-bearing. Every vertebral human body is linked to that cranial and also caudal counterparts by an intervertebral disk. The dorsal arch generally consists the a pair the pedicles occurring from the dorsal vertebral body, which hold together dorsally by a pair of level laminae. The two laminae sign up with at the midline developing a dorsal projection called the spinous process. The pedicles, laminae, and dorsum the the vertebral body type the vertebral foramen, a finish osseous ring the encloses the spinal cord. Its main duty is to safeguard the spinal cord and its linked vascular structures. Additionally, the transverse processes and the superior and also inferior articular processes are present near the junction of the pedicles and the laminae. In the cervical spine, the costal procedure becomes the anterior component of the transverse procedure that encloses the vertebral artery foramen.<2>
Unique features of the Cervical Spine
Despite displaying most common vertebral hallmarks, a far-reaching amount that anatomical variation exists within the cervical spine. The main function of the cervical spine is to support and promote the activity of the head and also neck. Big vertebral bodies space not essential considering the fairly small weight-bearing fill at this level. Thus, one increased variety of activity takes priority end vertebral size and also rigidity. However, the added motion and also flexibility may bring an enhanced risk for injury that the spinal cord and its linked neurovascular structures. All seven cervical vertebrae have actually a transverse foramen within your transverse processes, whereby a pair that vertebral arteries take trip cranially through the vertebrae starting at C6 before coursing medially over the arch the C1 in the direction of the foramen magnum. The spinous procedures of the C2 come C6 vertebrae are bifid, C1 has actually a posterior tubercle rather of a spinous process, and also C7 has a lot larger and singular spinous process, recognized as the vertebra prominens, i beg your pardon is similar to those in the thoracic vertebrae.<3>
The top Cervical Spine – The Axis (C1) and also the Atlas (C2)
The top cervical an ar of the cervical spine contains C1 and C2, which are an ext commonly described as the atlas and the axis, respectively. The main duty of the atlas is to support and also cradle the base of the occiput at the atlanto-occipital articulation. together such, over there are plenty of features unique to the atlas not shared with the remainder of the spine. many notably, the atlas lacks a vertebral body and also instead forms a huge ring-shaped fusion of anterior and also posterior arches that allows C1 come accommodate the spinal cord as it exit the foramen magnum. The atlas has pronounced concave and medially dealing with articular facets i beg your pardon accommodate the convex occipital condyles. This morphology helps the share contribute around fifty percent the flexion-extension of the neck yet limit lateral displacement the the occiput. This joints receive additional stabilization from solid soft-tissue ligaments the promote tight adherence to the occiput.<2><4>
The axis, or C2, additionally possesses distinctive anatomical features. Conversely, the atlas is responsible for accommodating the occiput, the axis is the main weight-bearing bone the the top cervical region. The hallmark attribute is that odontoid process, or dens, a bony projection expanding cranially from the vertebral body. It developed from the human body of the atlas and serves together the primary attachment allude for the soft tissues that stabilize the atlantoaxial junction. In contrast to the atlanto-occipital joint, the atlantoaxial junction is responsible for around fifty percent that the rotational motion of the cervical spine. The junction has actually three articulations: a midline atlanto-odontoid (or atlanto-dental) joint and also a pair the atlantoaxial page joints. The atlanto-odontoid share permits the anterior arch that the atlas to pivot top top the odontoid process. The lateral side joints show off the coupling of the atlas’ worse facets and also the exceptional facets the the axis; this joints are relatively shallow to enable for far-reaching motion.<2><3><4><5>
The Subaxial Cervical Spine – C3 to C7
All 5 vertebrae in this an ar share nearly identical morphological and functional features, and also compared come the top cervical spine, share most attributes with the typical vertebral anatomy. Distinct to these, all five vertebrae possess uncinate processes, which are bony prominences ~ above the lateral edges of the vertebral body the articulate in ~ Luschka joints to confer extr stability and also prevent vertebral listhesis.
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There additionally exist some minor functions of C7 that identify it from the remainder of the subaxial region. The transverse foramen of C7 is smaller sized in diameter than the remainder of the region and commonly does not home the vertebral arteries. Instead, the vertebral arteries cross anteriorly come the transverse procedures of C7 before proceeding cranially v the transverse foramina that C6. Additionally, C7 is taken into consideration a transitional vertebra, and as such, has a spinous procedure and inferior facets the resemble thoracic vertebrae. The vertebra additionally has a somewhat bigger vertebral body.<6>