Quick Facts
Location: Vertebral column.
Bone Type: Irregular bone.
Key Features: Vertebral body, laminae, pedicles, superior and inferior articular processes, and transverse and spinous processes.
Articulates With: Eighth and tenth thoracic vertebrae and ninth rib.
Arterial Supply: Posterior intercostal arteries.
Key Features & Anatomical Relations
The ninth thoracic vertebra (vertebra T9) is one of the twelve thoracic vertebrae of the vertebral column. It is classified as an irregular bone and includes the following bony features:
- parts: vertebral body, laminae, pedicles, superior and inferior articular processes, and transverse and spinous processes;
- surfaces: superior and inferior intervertebral surfaces, superior and inferior annular epiphyses, and vertebral arch;
- landmarks: superior and inferior vertebral notches, superior and inferior articular facets, and costal and transverse costal facets.
More information regarding these and other bony features can be found in the Parts, Surfaces, and Landmarks tabs for this bone.
The ninth thoracic vertebra is located:
- superior to the tenth thoracic vertebra;
- inferior to the eighth thoracic vertebra;
- medial to the ninth rib.
It articulates with the:
- eighth and tenth thoracic vertebrae at the intervertebral symphyses and zygapophyseal joints;
- ninth rib at the ninth costovertebral joint.
Ossification
Ossification of all thoracic vertebrae occurs at eight ossification centers, these are found in the:
- vertebral body, which appears in utero during the second to fourth months;
- right and left halves of the vertebral arch, with one center found in each, which appear in utero during the third month;
- right and left transverse processes, with one center found in each, which appear during puberty;
- spinous process, which appears during puberty;
- superior and inferior annular epiphyses, with one center found in each, which appear during puberty.
The ossification centers for the right and left halves of the vertebral arch fuse with each other during the first year after birth. The vertebral arch fuses with the vertebral body during the third year. The remaining centers fuse with the vertebral arch and body during early adulthood (Standring, 2016).
Variations
In some individuals:
- the costal facet of ninth thoracic vertebra may be present as a demifacet and not a complete facet, this occurs in instances where the head of tenth rib articulates with both the ninth thoracic and tenth thoracic vertebrae;
- the pedicles of thoracic vertebrae can display significant morphological variation;
- the transverse processes may fail to ossify (Tubbs, Shoja and Loukas, 2016).
Surface Anatomy
The spinous process of the ninth thoracic vertebra can be palpated, especially during flexion of the trunk.
List of Clinical Correlates
- Fracture
- Osteoporosis
- Spinal stenosis
- Scoliosis
- Spondylosis
- Spondylolisthesis
- Spondylolysis
- Butterfly vertebra
References
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.
Tubbs, R. S., Shoja, M. M. and Loukas, M. (2016) Bergman's Comprehensive Encyclopedia of Human Anatomic Variation. Wiley.
Learn more about this topic from other Elsevier products
Vertebra
A vertebra naturally moves in the direction of least bony resistance, which is strongly dictated by the specific plane of the articular surfaces of the facet joints.
