Thoracic Vertebrae (Thoracic Spine)

What is Dorsal Spine

The dorsal spine is the second and longest part of the spinal column, comprising 12 lumbar vertebrae, T1-T12. These 12 bones are divided by intervertebral discs. Their main function is to form the dorsal cage that shields the heart, lungs, and esophagus.

Where are the Dorsal Vertebrae Located

The dorsal vertebrae are arranged between the cervical and lumbar vertebral segments. They are situated in the dorsal area, nearly in the middle of the back.

Roles

• Defending the spinal cord and facilitating its passage through the tunnel at the center of the vertebral column as the vertebrae stack one after the other.
• Articulating with the ribs. All the dorsal vertebrae, except the two at the bottom (T11 and T12), form these articulations.
• Forming the rib cage and maintaining its stability, safeguarding all the vital internal organs, primarily the heart, and lungs.
• Supporting the body and permitting movement; however, this part has the least range of motion in the entire spinal column.

Structure of Dorsal Vertebrae

The dorsal spine consists of typical vertebrae with all the individual bones having a similar structure.

Vertebral body

Dorsal vertebrae have medium-sized and heart-shaped vertebral bodies, also known as corpus. Their primary function is to support body weight. As it approaches the lumbar vertebrae, the size of the vertebral bodies increases. On both sides of the vertebral body lie two concave cartilage-lined depressions, named superior and inferior costal facets, where the ribs get attached. Among the two facets, the superior one articulates with the head of the adjacent rib, and the inferior articulates with the head of the rib below.

Pedicles

Pedicles are cylindrical bony protrusions projecting from the posterolateral surfaces of the vertebral bodies. Their superior and inferior surfaces are marked with several notches that combine to form the intervertebral foramina. The dorsal spinal nerves pass through this foramen. On the posterior side, the pedicles articulate with the laminae on both sides, forming the neural arch. This arch fuses with the posterior surface of the vertebral body, creating the vertebral foramen. The foramen of the adjacent dorsal vertebrae line up to form the vertebral canal, through which the spinal cord passes.

Laminae

Laminae arise from the posterior side of the pedicles and extend towards the posterior midline, forming the spinous process.

Transverse Processes

These are long and thin wing-like structures projecting laterally from the junction between the pedicle from both sides of the vertebrae. The tubercle of the rib, along with several essential muscles and ligaments, attach here.

Articular Processes

Every dorsal vertebra features superior and inferior articular processes on both sides. Each of these processes has its corresponding articular facets, superior articular facet, and inferior articular facet. The former projects posteriorly and laterally, while the latter directs forward and medially.

Articulations

1. Intervertebral symphyses: The facet joints where the individual vertebra articulate with each other through intervertebral discs.
2. Costovertebral Joints: Synovial joints formed between the proximal head of the rib and its corresponding vertebrae.
3. Costotransverse Joints: Another group of synovial joints found between the rib’s tubercle and the corresponding vertebra’s transverse process.

Muscle and Ligament Attachments

Several muscles and ligaments attach to the dorsal vertebrae.

Muscles attached

1. Erector spinae
2. Interspinales
3. Intertransversarii
4. Latissimus dorsi
5. Multifidus
6. Rhomboid major
7. Rhomboid minor
8. Rotatores
9. Semispinalis
10. Serratus posterior (superior and inferior)
11. Splenius capitis
12. Splenius cervicis
13. Trapezius

Ligaments attached

1. Anterior longitudinal ligament
2. Supraspinous ligament
3. Posterior longitudinal ligament
4. Ligamentum flavum

References

1. 1. The Dorsal Spine — Teachmeanatomy.info
   2. Anatomy, Back, Dorsal Vertebrae — Ncbi.nlm.nih.gov
   3. Dorsal vertebrae — Kenhub.com
   4. Typical dorsal vertebrae — Radiopaedia.org
   5. Dorsal Vertebrae — Innerbody.com