There are twelve thoracic vertebrae and they are intermediate in size between the cervical and lumbar vertebrae; they increase in size going towards the lumbar vertebrae. They are distinguished by the presence of facets on the sides of the bodies for articulation with the heads of the ribs, as well as facets on the transverse processes of all, except the eleventh and twelfth, for articulation with the tubercles of the ribs. By convention, the human thoracic vertebrae are numbered T1–T12, with the first one (T1) located closest to the skull and the others going down the spine toward the lumbar region.
Thoracic Ligaments
The thoracic spine is strengthened by the presence of numerous ligaments.
Present Throughout Vertebral Column
- Anterior and posterior longitudinal ligaments: Long ligaments that run the length of the vertebral column, covering the vertebral bodies and intervertebral discs.
- Ligamentum flavum: Connects the laminae of adjacent vertebrae.
- Interspinous ligament: Connects the spinous processes of adjacent vertebrae.
- Supraspinous ligament: Connects the tips of adjacent spinous processes.
Unique to Thoracic Spine
A number of small ligaments also support the costovertebral joints:
- Radiate ligament of head of rib – Fans outwards from the head of the rib to the bodies of the two vertebrae and intervertebral disc.
- Costotransverse ligament – Connects the neck of the rib and the transverse process.
- Lateral costotransverse ligament – Extends from the transverse process to the tubercle of the rib.
- Superior costotransverse ligament – Passes from the upper border of the neck of the rib to the transverse process of the vertebra superior to it.
Thoracic Muscles
The muscles of the thorax consist of the intercostals and diaphragm. The intercostal muscles are arranged as three layers (external layer, internal layer and an incomplete innermost layer) between the ribs. The diaphragm closes the thoracic outlet and separates the thoracic cavity from the abdominal cavity. The three layers of the intercostal muscles are:
- external layer — external intercostal
- internal layer — internal intercostal
- innermost layer — transversus thoracic (anterior), innermost (lateral) and subcostal (posterior)
The diaphragm is the most important muscle of the thoracic wall. During normal respiration, this muscle is the primary component.
The innermost layer is split into three differently named muscle groups. The transversus thoracis, innermost intercostal and subcostal muscles make up the deepest layer of muscles from anterior to posterior, respectively.
Common conditions of thoracic muscles and ligaments include:
- Thoracic Intervertebral Joint Sprain
- Thoracic Muscle Rupture
- Costovertebral Joint Disorders.
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