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Unlocking the function of the thoracic vertebrae: How do they assist us in breathing and movement?
In vertebrates, the thoracic vertebrae are located in the middle of the spine, between the cervical and lumbar vertebrae. For humans, there are twelve thoracic vertebrae, which are between the cervical and lumbar vertebrae in size, and gradually increase in size as they approach the lumbar vertebrae. A notable feature of these thoracic vertebrae is that they have grooves on their sides for engagement with the heads of the ribs, and all thoracic vertebrae except the 11th and 12th have grooves on their transverse processes for engagement with the ribs. The tubercle is connected. The human thoracic vertebrae are conventionally numbered T1 to T12, with the first (T1) being the portion closest to the skull and the latter extending downward into the lumbar region.
General characteristics of the thoracic spine
The thoracic vertebrae in regions II to VIII have some common features. Just as the first and ninth to twelfth thoracic vertebrae have certain specificities, the vertebral bodies of these intermediate thoracic vertebrae are heart-shaped and are roughly equal in the anterior-posterior and left-right directions. These vertebrae are similar in appearance to the cervical and lumbar vertebrae, except for some variations in thickness. The back of their vertebrae is slightly thicker than the front, flat above and below, slightly convex on the front, deeply concave on the back, and slightly contracted on the sides and front. On each side, there are two half grooves of the ribs, one superior, close to the pedicle, and the other inferior, in front of the inferior intervertebral notch, which in the fresh state are covered with cartilage.
These features allow the thoracic spine to not only stabilize the spine, but also effectively support the ribs and facilitate breathing.
Detailed description of each thoracic vertebra
First thoracic vertebra (T1)
The first thoracic vertebra has complete rib head articular surfaces on both sides of the vertebral body, in addition to fused semi-grooves. This thoracic vertebra is similar in shape to the cervical vertebrae, being broad and concave with lip-like edges on either side. The superior articular surface is inclined upward and backward; while its transverse processes are long and lack grooves on the surface. Spinal nerve T1 passes beneath this vertebra.
Second thoracic vertebra (T2)
The second thoracic vertebra is larger than the first and resides beneath spinal nerve T2.
Third thoracic vertebra (T3)
The spinal nerve T3 from the third thoracic vertebra passes downward at this location.
Fourth thoracic vertebra (T4)
The fourth and fifth thoracic vertebrae are located at the same level of the sternal angle, and the spinal nerve T4 passes below them.
Fifth thoracic vertebra (T5)
The fifth thoracic vertebra is also located at the same level as the fourth thoracic vertebra, and is the location where the human trachea divides into two main bronchi, with the spinal nerve T5 passing outside of it.
The sixth thoracic vertebra (T6) to the eighth thoracic vertebra (T8)
The sixth to eighth thoracic vertebrae are all described as relative characteristics. The spinal nerves pass under these vertebrae, and the eighth and ninth thoracic vertebrae are located on the xiphoid plane.
The ninth thoracic vertebra (T9) to the twelfth thoracic vertebra (T12)
The ninth thoracic vertebra may have no groove at the bottom, and some individuals may have two and a half grooves on each side, while the tenth thoracic vertebra has only a groove at the top. The tenth thoracic vertebra is a complete articular facet, whereas the eleventh and twelfth thoracic vertebrae have features similar to those of the lumbar vertebrae. The twelfth thoracic vertebra has a convex and outward-pointing inferior articular surface, and its transverse processes can be subdivided into three protuberances.
Diversity of thoracic vertebrae and other animals
In other groups of animals, the number of thoracic vertebrae varies greatly. For example, while most marsupials have 13 thoracic vertebrae, koalas have only 11. Mammals usually have between 12 and 15 thoracic vertebrae, but horses, tapirs, rhinos and elephants may have 18 to 20. Some sloths may have as many as 25, while whales have just nine.
The structure of the thoracic vertebrae varies between species and shows many evolutionary adaptations.
In summary, the thoracic vertebrae play a key role in our spinal system. They not only support and protect the spinal cord, but are also closely related to breathing and movement. So, have you ever thought about how important a role these thoracic vertebrae play in our daily lives?
