The vertebral column is part of the axial skeleton and forms by series of bones called vertebrae. The main functions of the vertebral column include the support of the head, protection and enclosure of the spinal cord, formation of the posterior aspect of the thoracic cage (site of ribs attachment), attachment of muscles of the upper limb and back, and participation in the pelvic girdle formation. The vertebral column can be divided into five different regions: cervical, thoracic, lumbar, sacral, and coccygeal. The total number of vertebrae is 33. The last two regions, the sacral and coccygeal, are formed by initially individual vertebrae that fuse during the development of the body.
The distribution of the vertebrae per region is the following:
7 Cervical vertebrae in the region of the neck
12 Thoracic vertebrae posterior at the thoracic cavity
5 Lumbar at the lower back
5 Sacral fused vertebrae form the sacrum.
3-4 Coccygeal fused vertebrae form the coccyx.
Each vertebra consists anteriorly of the vertebral body and posteriorly of the vertebral arch. Fibrocartilaginous intervertebral discs separate the vertebral bodies. The superior and inferior aspects of the vertebral body are lined with hyaline cartilage. The vertebral arch forms the lateral and posterior aspects of each vertebra. The vertebral arch consists of multiple bony projections. The pedicles form the base of the arch. The pedicles connect the vertebral body to the transverse processes. Each vertebra has two transverse processes, which extend laterally and posteriorly from the vertebral body. In thoracic vertebrae, the transverse processes articulate with the ribs. The lamina connects the transverse processes with the spinous process. Each vertebra has a single spinous process located posteriorly at the point of the arch.
In the meanwhile, near the junction of the pedicle with the lamina, there are an additional four processes: two superior articular processes and two inferior articular processes for articulation with respective vertebrae superiorly and inferiorly.
The vertebral foramen is located between the vertebral body and the vertebral arch contains the spinal cord with the meninges, blood vessels, adipose fat, and connective tissue. The intervertebral foramina are bilateral openings of the spinal column between vertebrae and give passage to the spinal cord’s spinal nerves.
Many vertebral levels are associated with significant anatomical landmarks and structures:
C3 Hyoid bone
C4 Common carotid artery bifurcation & thyroid cartilage
C6 Cricoid cartilage, inferior end of the larynx, trachea start, end of pharynx, the beginning of the esophagus
T2 Sternoclavicular joint (sternal angle of Louis)
T4 Carina (bifurcation of the trachea), Sternal angle (costal cartilages of the second rib articulates with the sternum), arch of aorta, division between superior and inferior mediastinum, azygos vein drains into superior vena cava.
T8 Inferior vena cava hiatus of the diaphragm
T10 Esophageal hiatus of the diaphragm
T12 Aortic hiatus of the diaphragm
L1 Hilum of the left kidney
L1-L2 Spinal cord termination
L2 Hilum of the right kidney, Thoracic duct
L4 Abdominal aorta bifurcation to right and left common iliac arteries
L5 Inferior vena cava formation from the right and left common iliac veins, Cauda equina termination
S1 Sacral promontory
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