the vertebra. The arch is located behind the vertebral body. The vertebral arch is attached to the body with the help of two pedicles of vertebral arch, pediculi arcus vertebrae, thus bounding the vertebral foramen, foramen vertebrale (fig. 2.1).
The foramina of all vertebrae form the vertebral canal, canalis vertebralis, enclosing the spinal cord. Openings for blood vessels named nutrient foramina, foramina nutricia, are visible on the surface of the vertebral body.
Seven processes project from the vertebral arch. An unpaired spinous process, processus spinosus, projects dorsally along the median line. The paired transverse processes, processus transversus, project on the right and on the left in the frontal plane. The paired superior and inferior articular processes, processus articularis superior et processus articularis inferior, project up and down from the arch. The bases of the articular processes bound the superior and inferior vertebral notches, incisura vertebralis superior et incisura vertebralis inferior. The inferior notches are deeper than the superior ones. When the vertebrae are articulated with each other, the inferior and superior notches form an intervertebral foramen, foramen intervertebrale, on the right and on the left. The intervertebral foramina transmit spinal nerves and blood vessels.
Fig. 2.1. Thoracic vertebra:
a – lateral aspect: 1 – vertebral body (corpus vertebrae); 2 – superior costal demi-facet (fovea costalis superior); 3 – superior vertebral notch (incisura vertebralis superior); 4 – superior articular process (processus articularis superior); 5 – transverse process (processus transversus); 6 – transverse costal facet (fovea costalis processus transversi); 7 – spinous process (processus spinosus); 8 – inferior articular process (processus articularis inferior); 9 – inferior vertebral notch (incisura vertebralis inferior); 10 – inferior costal demi-facet (fovea costalis inferior)
b – superior aspect: 1 – spinous process (processus spinosus); 2 – vertebral arch (arcus vertebrae); 3 – pedicles of vertebral arch (pediculi arcus vertebrae); 4 – superior costal demi-facet (fovea costalis superior); 5 – superior articular process (processus articularis superior); 6 – transverse costal facet (fovea costalis processus transversi); 7 – transverse process (processus transversus)
2.2. Cervical Vertebrae
The cervical vertebrae, vertebrae cervicales (CI– CVII), form the upper (cervical) part of the vertebral column. Two upper cervical vertebrae of seven significantly differ from other ones, therefore, they are termed atypical vertebrae. We will study them later. The other five vertebrae are structured according to the general principle: their bodies are relatively small, have an ellipsoid form, the vertebral foramen is large and triangular.
The distinctive feature of all cervical vertebrae is the presence of transverse foramina, foramen transversarium, in the transverse processes. They are formed as a result of the fusion of the transverse processes and the rudiments of the cervical ribs. The vertebral artery and vein pass through these foramina.
The groove for spinal nerve, sulcus nervi spinalis, passes along the superior surface of the transverse prosesses of the III–VII cervical vertebrae. These processes end with two tubercles – anterior and posterior, tuberculum anterius et tuberculum posterius. The anterior tubercle of the VI vertebra is more developed than the anterior tubercles of other cervical vertebrae. It is termed carotid tubercle, tuberculum caroticum, because the carotid artery can be compressed to it during hemorrhage.
The spinous processes are short and directed downwards, and their ends are bifurcated. The spinous process of the VII cervical vertebra is the longest, and its end is thickened. This vertebra is called prominent, vertebra prominens, because the apex of its spinous process is clearly palpated in a living person.
The articular processes of the cervical vertebrae are short and located obliquely between the frontal and horizontal planes. Meanwhile, the superior articular processes are directed backwards and slightly upwards, the inferior articular processes are directed forwards and slightly downwards (fig. 2.2).
Fig. 2.2. Typical cervical vertebra (superior aspect):
1 – vertebral body (corpus vertebrae); 2 – transverse process (processus transversus); 3 – superior articular process (processus articularis superior); 4 – spinous process (processus spinosus); 5 – transverse foramen (foramen transversarium)
The shape of the first two cervical vertebrae is influenced by their close location to the skull. They are involved in head turning. Therefore, they are termed «rotational vertebrae».
The I cervical vertebra is called the atlas, atlas (CI). It differs from the general structure of individual vertebrae: it has no body no notches and no spinous or articular processes (fig. 2.3).
The atlas has an anterior arch, arcus anterior atlantis, instead of the body. Its anterior surface has an anterior tubercle, tuberculum anterius; on its posterior surface there is a small articular facet, fovea dentis, with which the II cervical vertebra is joined.
The lateral masses of atlas, massae laterales atlantis, are located on the both sides. Each of them bears an ellipsoid, concave superior articular surface, facies articularis superioris, joining with the corresponding occipital condyle. The inferior articular surfaces, facies articulares inferiores, form round, slightly concave articulate areas connected with the II cervical vertebra.
Fig. 2.3. I cervical vertebra (atlas) (superior aspect):
1 – anterior arch of atlas (arcus anterior atlantis); 2 – lateral mass (massa lateralis); 3 – transverse foramen (foramen transversarium); 4 – transverse process (processus transversus); 5 – groove for vertebral artery (sulcus arteriae vertebralis); 6 – posterior arch of atlas (arcus posterior atlantis); 7 – posterior tubercle (tuberculum posterius); 8 – superior articular surface (facies articulars superior); 9 – anterior tubercle (tuberculum anterius); 10 – facet for dens (fovea dentis)
The posterior arch of the atlas, arcus posterior atlantis, corresponds to the arch of a typical vertebra. There is a reduced spinous process in the form of a small posterior tubercle, tuberculum posterius, on the back surface of the posterior arch. The groove for vertebral artery, sulcus arteriae vertebralis, passes on the superior surface of the posterior arch behind the lateral mass.
The vertebral foramen, foramen vertebrale, is bounded with arches and lateral masses. It is much larger than the vertebral foramina of other vertebrae, and only its posterior part corresponds to them. In its anterior part narrowed on the sides with the lateral masses, the dens of the II cervical vertebra is located. The transverse process, рrocessus transversus, is perforated by the transverse foramen, foramen transversarium, for the passage of blood vessels like transverse processes of the other cervical vertebrae. The ends of the transverse processes are slightly thickened. They have no anterior and posterior tubercles and no the groove for spinal nerve.
Fig. 2.4. II cervical vertebra (axis) (posterior aspect):
1 – dens (dens); 2 – superior articular facet (facies articularis superioris); 3 – spinous process (processus spinosus); 4 – transverse process (processus transversus); 5 – transverse foramen (foramen transversarium)
