The vertebral column extends from the skull to the pelvis and consists of 33 vertebrae, which are differentiated into five regions: the cervical spine (C1–C7), the thoracic spine (T1–T12), the lumbar spine (L1–L5), the sacrum (S1–S5; fused in adults), and the coccyx (3–5 fused bones). The functions of the vertebral column include protecting the spinal cord within the vertebral canal; transferring the weight of the upper body to the pelvis; articulating with the skull, ribs, and pelvis; and providing attachment for musculature. It is, furthermore, the main site of hematopoiesis besides the pelvis. The basic vertebra consists of a vertebral body (anterior), a vertebral arch (posterior), and a vertebral foramen, through which runs the spinal cord. More specific morphological features vary according to the region and associated function. Adjacent vertebrae articulate via intervertebral discs and facet joints, and there are specialized joints in the upper cervical region, the thoracic region, and between the sacrum and pelvis for articulation with the head and neck, the ribs, and the hip respectively. Embryologically, the vertebrae are derived from the somites of the paraxial mesoderm, and the nucleus pulposus of the intervertebral discs is derived from the notochord.
- Protection of the spinal cord, spinal nerve roots, and associated vasculature
- Transfer of weight from the upper body to the pelvis
- Articulation with the skull, ribs, and pelvis
- Articulations between vertebrae allow for flexion, extension, rotation, and lateral flexion of the trunk
- Attachment site for muscles, including the and
- Main site of pelvis besides the
|Spinal segment||Number of vertebrae||Short term||Curvature|
Basic vertebral structure
- Cylindrical anterior part of the vertebra responsible for weight bearing
- Contains red bone marrow
- Articulates with the vertebral bodies above and below via the intervertebral disc
Consists of two pedicles (laterally) and two laminae (posteriorly) with several vertebral processes
- Vertebral pedicles
- Vertebral laminae
- Lateral space between the pedicles of two adjacent vertebrae, from which spinal nerves and their vessels emerge
- Spinous process: single posterior midline process emerging at the junction of the two laminae
- Transverse processes
- Flat surfaces at the junction of the pedicles and laminae, two superiorly and two inferiorly, that articulate with the articular processes of the adjacent vertebrae, forming the zygapophyseal (facet) joints
- The region between the superior and inferior articular processes at the junction of the pedicle and lamina is called the pars interarticularis.
- Central space between the vertebral arch and vertebral body
- All vertebral foramina together form the vertebral canal, containing:
- C1 (atlas)
- C2 (axis)
- The vertebral arteries, veins, and sympathetic fibers pass through the transverse foramina in the transverse processes of C6–C1 before entering the foramen magnum.
- Have large the largest vertebral foramina to accommodate the cervical enlargement of the spinal cord.
- C2–C6 have bifid spinal processes.
- C7 (vertebra prominens) has a large, easily palpable spinal process to which the ligamentum nuchae attaches.
- Thoracic vertebrae
- Lumbar vertebrae
- Formed by 5 fused vertebrae; forms the posterosuperior wall of the pelvis
- Articulates with the L5 cranially, the ilia laterally, and the coccyx caudally
- The sacral nerves emerge through the anterior and posterior sacral foramina between the central and lateral masses.
- The female sacral promontory is smaller and the sacrum is shorter and less curved than the male one, contributing to the larger pelvic inlet required for childbirth.
- The sacral hiatus is the caudal opening of the vertebral canal on the dorsal surface of the sacrum at the level of S5 medial to the sacral horns (cornua), it is the exit point for the S5 nerves.
Specific vertebra levels are associated with key anatomical landmarks: e.g., C4 (bifurcation of common carotid artery), T2 (aortic arch), T4 (bifurcation of trachea), L1 (end of spinal cord in adults), L3 (end of spinal cord in newborns), and L4 (level of iliac crest; bifurcation of aorta).
Joints of the spine 
- Atlanto-occipital joints
- Atlanto-axial joints
Intervertebral joints (C2–S1)
- Adjacent vertebral bodies are linked by fibrocartilage intervertebral discs, which function as shock absorbers.
- They consist of:
- The vertebral endplate is a thin layer of hyaline cartilage between the vertebra and the disc.
- Discs are thickest in the lumbar region and thinnest in the upper thoracic region.
- There is no intervertebral disk between the atlas and the axis.
- Facet joints (zygapophysial joints)
- Costovertebral joints
- Costotransverse joints: synovial joints between the transverse costal facets on the transverse processes of T1 to T9/T10 and the rib tubercle of the rib inferior to the vertebral level
- Sacroiliac joints
is the oss of ligamentous stability between atlas (C1) and axis (C2), which may cause the odontoid process to compress the spinal cord, medulla, or vertebral arteries when the neck is flexed. It is most commonly caused by Down syndrome, rheumatoid arthritis, or trauma. 
Ligaments of the spine
|Overview of the ligaments of the spine|
|Anterior longitudinal ligament|
|Posterior longitudinal ligament|
|Ligamenta flava|| |
|Supraspinous ligament|| |
The narrowing of the posterior longitudinal ligament leaves the annulus fibrosus without support in the posterolateral region, increasing the likelihood of disk herniations in this region, which may cause compression of the spinal nerve at the level below (e.g., herniation of the L4/5 disk compresses the L5 nerve)!
During lumbar puncture, the needle pierces the following structures in order before it reaches the subarachnoid space: skin, subcutaneous tissue, supraspinal ligament, interspinal ligament, ligamentum flavum, epidural space, dura mater, and arachnoid mater.
- The intrinsic muscles of the back are innervated by dorsal rami of the spinal nerves and enable extension, rotation, and lateral flexion of the head and spine.
- For other muscles attaching to the vertebrae, see:
Vasculature and lymphatics
|Vasculature and lymphatics of the vertebral column|
|Cervical vertebrae|| || |
|Thoracic vertebrae|| || |
|Lumbar vertebrae|| || |
- Vertebrae, facet joints, superficial ligamenta flava, and overlying skin: dorsal rami of the spinal nerves
- Walls of the vertebral canal, dura mater, outer annulus of intervertebral discs, and deep ligamenta flava: sinuvertebral nerves
- Atlanto-occipital and atlanto-axial joints: ventral rami of the C1 and C2 nerves
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Embryology and development
- Sclerotome cells migrate from the somite toward the midline and surround the notochord, forming the vertebral body.
- The vertebral bodies are each derived from parts of two sclerotomes
- Sclerotome migrates dorsally to form the vertebral arch, surrounding the neural tube
- Ossification starts in 8th week of embryonic development
- Development of spinal curvatures
- Congenital and developmental abnormalities
- Pott disease) (