The thoracic spine is the central part of the vertebral column, located between the cervical spine (neck) and the lumbar spine (lower back). It comprises 12 vertebrae, each designated T1 through T12 (from superior to inferior).
General Characteristics of Thoracic Vertebrae
Each thoracic vertebra shares common characteristics:
Vertebral Body: The bodies of the thoracic vertebrae are larger than those in the cervical region and are heart-shaped when viewed from above. The bodies increase in size moving down the spine, as each vertebra must bear more weight.
Vertebral Foramen: This is the hole through which the spinal cord passes. It is smaller in the thoracic region than in the cervical or lumbar regions due to the relative size of the spinal cord segments at this level.
Spinous Processes: These project posteriorly from the vertebrae and are angled sharply downward. They serve as attachment points for muscles and ligaments.
Transverse Processes: These project laterally from the vertebrae and are unique in the thoracic spine because they have facets that articulate with the tubercle of the ribs. This is a characteristic feature of the thoracic vertebrae.
Specific Characteristics of Thoracic Vertebrae
The 12 thoracic vertebrae all have unique characteristics, mainly dealing with their articulations with the ribs:
T1: Has a full facet on the body for the head of the first rib and a demi-facet for the second rib.
T2-T8: These vertebrae have demi-facets on their bodies for the articulation with the head of the ribs. There is a superior demi-facet for the rib of the same number and an inferior demi-facet for the rib below.
T9-T11: Have a single facet on their bodies for the articulation with the head of the rib of the same number.
T12: Like T1, has a full facet on the body for the head of the twelfth rib and looks similar to a lumbar vertebra.
The articulation with the ribs and the downward angle of the spinous processes limit the flexibility of the thoracic spine compared to the cervical and lumbar regions. Still, this structure provides a strong protective cage (the thorax) for vital organs like the heart and lungs. Intervertebral discs between each pair of thoracic vertebrae provide cushioning and flexibility.