Structure of a vertebra
The basic structure of a vertebral body consists of a vertebral body (corpus vertebrae), a vertebral arch (arcus vertebrae), a vertebral hole, a spinous process (proc. spinosus), two transverse processes (procc. transversi) and four articular processes (procc. articulares). The main load is borne by the ventrally located vertebral body. The vertebral foramen (foramen vertebrale) is enclosed by the vertebral bodies and vertebral arches. All vertebral holes together form the vertebral canal (Canalis vertebralis). The spinal cord is located in the vertebral canal. Since the vertebral bodies of the lower section of the spine carry most of the load, they are also larger. The individual vertebral bodies are intertwined by the spinal discs (only exception: axis and atlas). The appendixes act as the base for the muscles and ligaments; in the region of the thoracic vertebral bodies they form the rib-vertebral joints.
Typical vertebrae from different areas of the spine
The vertebrae vary in the different regions of thespine with regard to their size and their special characteristics. On one side, the vertebral bodies enlarge from cranial to caudal and on the other side, the vertebral holes gradually shrink as the spinal cord becomes narrower. Furthermore, the appearance of the vertebral arches and the adjoining appendages changes.
The figure on the right shows:
- A - Fifth cervical vertebrae
- B - Sixth thoracic vertebrae
- C - Third lumbar vertebrae
motion segment
Spinal motion segment is the functional unit that two adjacent vertebrae including the intermediate spinal disc (synchondrosis) and the adjacent intersegmental musculature together form.
Furthermore, it describes the comprehensive interaction of all bony, cartilaginous, ligamentary, and muscular components of a defined spinal segment.
Thus, the spinal motion segment forms the smallest functional unit of the spinal column.
Within the Viewer a motion segment is shown by example of 12th thoracic vertebra and 1st lumbar vertebra (to start click here ) :
The motion segment is marked red.
1. vertebral body
2. vertebral arch
3. spinal disc
4. vertebral joint
5. ligament between the spinous processes
6. exit canal of the nerve
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