What is the Difference Between Thoracic and Lumbar Vertebrae

The main difference between thoracic and lumbar vertebrae is that the body of the thoracic vertebrae is comparatively large whereas the body of the lumbar vertebrae is the largest body. Furthermore, the spinous process of the thoracic vertebrae is long and fairly thick while it is short and blunt in lumbar vertebrae. Moreover, the transverse processes of the thoracic vertebrae are fairly large while that of the lumbar vertebrae are large and blunt.

Thoracic and lumbar vertebrae are the two types of vertebrae groups found in the middle and the lower part of the spine. Human spine consists of 12 thoracic and 5 lumbar vertebrae.

Key Areas Covered

1. What are Thoracic Vertebrae
     – Definition, Structure, Importance
2. What are Lumbar Vertebrae
     – Definition, Structure, Importance
3. What are the Similarities Between Thoracic and Lumbar Vertebrae
     – Outline of Common Features
4. What is the Difference Between Thoracic and Lumbar Vertebrae
     – Comparison of Key Differences

Key Terms

Facets, Lumbar Vertebrae, Spinous Process, Thoracic Vertebrae, Transverse Process, Vertebral Body

What are Thoracic Vertebrae

Thoracic vertebrae are the vertebrae which make up the middle part of the spine. 12 thoracic vertebrae occur in the human spine. They are named as T1-T12. In contrast to the cervical vertebrae, thoracic vertebrae are larger and stronger. The spinous process of the T1 and T2 vertebrae are long, laterally flattened, and directed inferiorly. On the contrary, the spinous process of the T11 to T12 are shorter, broader, and directed posteriorly. In addition, the transverse processes of thoracic vertebrae are longer when compared to that of the cervical vertebrae.

Figure 1: Thoracic Vertebra

Significantly, each thoracic vertebra consists of articulating surfaces called facets and demifacets to the ribs. Therefore, the main function of the thoracic vertebrae is to protect the internal organs of the thorax including the heart and lungs by holding the rib cage.

What are Lumbar Vertebrae

Lumbar vertebrae are the vertebrae with the largest vertebral body. They occur below the thoracic vertebrae and above the sacrum. There are 5 lumbar vertebrae in humans; they are named as L1-L5. They are the largest and the strongest vertebrae in the spinal column. Therefore, they support most of the body weight.

Figure 2: Lumbar Vertebra

As a result of this, the superior articulate facets occur medially instead of superiorly. Also, the inferior articulate facets occur laterally, instead of inferiorly. In addition, the spinous process of the lumbar vertebrae are thick and broad. It projects posteriorly, providing attachment points to large back muscles.

Similarities Between Thoracic and Lumbar Vertebrae

• Thoracic and lumbar vertebrae are two groups of vertebrae which occur in the middle and the lower part of the spine of vertebrates.
• Vertebral body, pedicles, spinous process, transverse processes, articular facets, and spinal canal are the main parts of both types of vertebrae.
• Also, both contain one intervertebral foramina.
• Besides, the spinal cord runs through the spinal canal.
• And, the invertebral disks occur in between each vertebrae.

Difference Between Thoracic and Lumbar Vertebrae

Definition

Thoracic vertebrae refer to the each of the twelve bones of the backbone to which the ribs are attached while lumbar vertebrae refer to the any of the vertebrae situated below the thoracic vertebrae and above the sacrum. Thus, this is the fundamental difference between thoracic and lumbar vertebrae.

Location

Moreover, thoracic vertebrae occur after the cervical vertebrae while lumbar vertebrae occur below the thoracic vertebrae.

Number

Twelve thoracic vertebrae and five lumbar vertebrae occur in humans. Hence, this is another difference between thoracic and lumbar vertebrae.

Vertebral Body

Also, while the vertebral body of the thoracic vertebrae is comparatively large, the vertebral body of the lumbar vertebrae is the largest.

Spinous Process

Furthermore, the spinous process of the thoracic vertebrae is long and fairly thick while the spinous process of the lumbar vertebrae is short and blunt.

Transverse Processes

Transverse processes is another difference between thoracic and lumbar vertebrae. The transverse processes of the thoracic vertebrae are fairly large while the transverse processes of the lumbar vertebrae are large and blunt.

Articular Facets for Ribs

Besides, thoracic vertebrae contain articular facets for ribs while lumbar vertebrae do not contain articular facets for ribs.

Inferior Articular Facets

Additionally, one other difference between thoracic and lumbar vertebrae is that the inferior articular facet of the thoracic vertebrae is anteromedial while the inferior articular facet of the lumbar vertebrae is lateral.

Superior Articular Facets

Furthermore, the superior articular facet of the thoracic vertebrae is posterolateral while the superior articular facet of the lumbar vertebrae is medial.

Size of the Intervertebral Disk

Another difference between thoracic and lumbar vertebrae is that the intervertebral disk of the thoracic vertebrae is thin while the intervertebral disk of the lumbar vertebrae is massive.

Size of the Spinal Canal

The spinal canal of the thoracic vertebrae is large while the spinal canal of the lumbar vertebrae is comparatively small.

Direction of Curving

One more difference between thoracic and lumbar vertebrae is that thoracic vertebrae curve in the posterior direction while lumbar vertebrae curve in the anterior direction.

Importance

In addition, thoracic vertebrae provide attachment sites for ribs while lumbar vertebrae help in maintaining the vertical posture above the pelvis.

Conclusion

Thoracic vertebrae are the vertebrae which occur at the middle part of the spine. Humans have 12 thoracic vertebrae. They consist of a long and fairly thick spinous process and fairly large transverse processes. In comparison, lumbar vertebrae occur below the thoracic vertebrae and above the sacrum. There are 5 lumbar vertebrae in the spine in humans. Significantly, their vertebral body is the largest among the other types of vertebrae in the spine. Therefore, the main difference between thoracic and lumbar vertebrae is the features of its components.

References:

1. “Anatomy of the Spine.” MAYFIELD Brain & Spine, Available Here

Image Courtesy:

1. “Thoracic vertebrae” By Anatomist90 – Own work (CC BY-SA 3.0) via Commons Wikimedia  
2. “Lumbar vertebrae” By Anatomist90 – Own work (CC BY-SA 3.0) via Commons Wikimedia