Anatomy of the Spine - The Spinal or Vertebral Column

Vertebral Column
Thirty-three vertebral bodies make up the spinal or vertebral column. The spinal column is divided into five regions; cervical (neck), thoracic (chest), lumbar (low back), sacrum (pelvis), and coccyx (tailbone). The vertebrae are the bony elements of the column.

Term
# of Vertebrae
Body Area
Abbreviation
Cervical
7
Neck
C1 - C7
Thoracic
12
Chest
T1 - T12
Lumbar
5 or 6
Low Back
L1 - L5
Sacrum
5 (fused)
Pelvis
S1 - S5
Coccyx
3
Tailbone
None

Cervical Spine (Neck)
There are 7 vertebrae in the cervical spine abbreviated C1 through C7.

C1 and C2 are often referred to as the upper cervical region. C3 through C7 is the lower cervical region. C1 and C2 are unique.

Atlas (C1)
The first cervical vertebra is the atlas. It is circular in shape and functions to support the skull. There are two lateral (side) bony masses that join at the front and back known as the anterior and posterior arches.

Axis (C2)
The dens is a tooth-like bone that projects upward; it is also called the odontoid process. The atlas and skull pivots and rotates around the dens.

Thoracic Vertebrae
There are 12 vertebrae in the thoracic spine abbreviated T1 through T12.

1-Vertebral Body 2-Spinous Process 3-Transverse Facet
4-Pedicle 5-Foramen 6-Lamina 7-Superior Facet

The thoracic spine is especially stable and strong because of its long spinous processes and attachment to the rib cage. However, the ribs do not attach to T11 and T12 and are called floating ribs.


Lumbar Vertebrae (Low Back)
There are 5 lumbar vertebrae abbreviated L1 through L5. Starting with L1, each vertebral body is gradually larger than the one above. The lumbar vertebrae are the largest and strongest in the spine. These vertebral bodies distribute and carry most of the body’s weight and stress at rest and during movement. When compared to the thoracic vertebrae, the pedicles are wider and longer and the spinous processes are broader and square-shaped.

Purpose of the Vertebrae
Although vertebrae range in size; cervical the smallest, lumbar the largest, vertebral bodies are the weight bearing structures of the spinal column. Upper body weight is distributed through the spine to the sacrum and pelvis. The natural curves in the spine, kyphotic and lordotic, provide resistance and elasticity in distributing body weight and axial loads sustained during movement.

The vertebrae are composed of many elements that are critical to the overall function of the spine, which include the intervertebral discs and facet joints.

Functions of the Vertebral or Spinal Column Include:

Protection
• Spinal Cord and Nerve Roots
• Many internal organs

Base for Attachment
• Ligaments
• Tendons
• Muscles

Structural Support
• Head, shoulders, chest
• Connects upper and lower body
• Balance and weight distribution

Flexibility and Mobility
• Flexion (forward bending)
• Extension (backward bending)
• Side bending (left and right)
• Rotation (left and right)
• Combination of above

Other
• Bones produce red blood cells
• Mineral storage

Sacral Spine
Behind the pelvis is the sacral spine or sacrum. The sacrum is made up of 5 fused vertebrae abbreviated S1 through S5. In the illustration on the right, the sacrum is rectangular in shape and, if viewed from the front of the body, could be seen to fit in between each hip bone. The fifth lumbar vertebra (L5) moves or articulates with the S1 joint.

Coccyx (Tailbone)
Five fused bones make up the coccyx or tailbone; the end of the spinal or vertebral column. These bones are not shaped like any other spinal bone. The coccyxgeal bones are solid bones and do not have holes from which nerves branch out through into other parts of the body.

Purpose of the Spinal Column