Bones - Thoracic Spine Flashcards
Where is the thoracic segment located?
How many thoracic vertebrae are there?
This is the second segment of the vertebral column. It consists of twelve thoracic vertebrae that are separated by intervertebral discs.
Characteristic features?
The thoracic vertebrae have four features that distinguish them from the other vertebrae:
1) Body is heart-shaped
2) Presence of demi-facets of the sides of each vertebral body - this articulates with the heads of the ribs.
3) Presence of costal facets on the transverse processes - these articulates with the tubercles of the ribs. They are present on T1-T10 only.
4) The spinous processes are long and slant inferiorly. This offers increased protection to the spinal cord, preventing an object such as a knife entering the spinal cord.
Superior and inferior constal demi-facets?
The superior and inferior costal facets are located on the sides of each vertebral body. They consist of cartilage lined depressions, which articulate with the heads of the ribs. The superior facet articulates with the head of the adjacent rib, and the inferior facet articulates with the head of the rib below.
In the majority of the vertebrae (T2-T9) these facets are demi-facets. There are some atypical vertebrae that possess whole facets.
Atypical vertebrae?
The atypical thoracic vertebrae display variation in the size location and number of the superior and inferior costal facets.
1) T1 - superior facet is not a demi-facet, as this is the only vertebrae to articulate with the 1st rib.
2) T10 - a single pair of whole facets is present which articulate with the 10th rib. These facets are located across both the vertebral body and the pedicle.
3) T11 and T12 - each have a single pair of entire costal facets, which are located on the pedicles.
Joints?
Present throughout the vertebral column
1) Between vertebral bodies - adjacent vertebral bodies are joined by intervertebral discs, made of fibrocartilage. This is a type of cartilaginous joint, known as a symphysis.
2) Between vertebral arches - formed by the articulation of superior and inferior articular processes from adjacent vertebrae. It is a synovial type joint.
Unique to the thoracic spine
1) Costovertebral joint - consists of the head of the rib articulating with:
i) Superior costal facet of the corresponding vertebra
ii) Inferior costal facet of the superior vertebra
iii) Intervertebral disc separating the two vertebrae
Within this joint, the intra-articular ligament of the head of the rib attaches to the rib head to the intervertebral disc. Only slight gliding movements can occur at these joints, due to the close articulation of their components.
2) Costotransverse joint - formed by articulation with the transverse processes of the thoracic vertebrae and the tubercle of the adjacent rib. They are present in all vertebrae except T11 and T12.
Ligaments?
Present throught the vertebral column
1) Anterior and posterior longitudinal ligaments
2) Ligamentum flavum
3) Interspinous ligament
4) Supraspinous ligament
Unique to the thoracic spine
1) Radiate ligament of the head of the rib - fans outwards from the head of the rib to the bodies of the two vertebrae and intervertebral disc.
2) Costotransverse ligament - connects the neck of the rib and the transverse process.
3) Lateral costotransverse ligament - extends from the transverse process to the tubercle of the rib.
4) Superior costotransverse ligament - passes from the upper border of the neck of the rib to the transverse process of the vertebra superior to it.
Clinical relevance - thoracic kyphosis?
Kyphosis is an excessive curvature of the thoracic spine, causing the back to appear ‘hunched’. It may occur for a number of reasons early in life. These include poor posture, abnormally wedge-shaped vertebrae (Scheuermann’s kyphosis), and fusing of vertebrae during development.
Various disease can also lead to kyphosis in adults. The most common cause is osteoporosis - a condition whereby bone mass is lost (mostly in older people). This leaves the spine less able to support the weight of the body, thus resulting in a characteristic kyphosis.
