Anatomy of the Spine
The spinal or vertebral column is made up of individual bones called the vertebrae. It extends from the skull to the pelvis. The vertebrae comprise three main groups, the cervical, the thoracic, and the lumbar spine. The lumbar vertebrae are stacked on the sacrum which attaches to the pelvis. Below the sacrum is the coccyx or tailbone.
The purpose of the vertebrae are to protect the spinal cord and to bear weight through the vertebral bodies. Upper body weight is distributed through the spine to the sacrum and pelvis. The natural curves of the spine give the spine resistance and elasticity in distributing body weight and axial loads during body movement.
Cervical Spine
There are seven cervical vertebrae which form a lordotic curve. The first two cervical vertebrae are specialized vertebrae. C1 or the atlas supports the skull. It is a ring of bone made of two lateral masses connected to the front and back by anterior and posterior arches. C2 or the axis is also called the dens. It allows the head and the atlas to rotate around the dens. The cervical vertebrae are the smallest vertebrae.
Thoracic Spine
The thoracic vertebrae gradually increase in size from T1-T12 and form a kyphotic curve. They have small pedicles, long spinous processes, and large intervertebral foramen through which the spinal nerves pass. There is less nerve compression in this area. The rib cage attaches to the thoracic vertebrae. At T11 and T12 the ribs do not attach to the rib cage and are called floating ribs. ROM is limited in the thoracic spine due to the long spinous processes and many rib/vertebral connections.
Lumbar Spine
The lumbar spine is made up of five vertebrae which gradually increase in size and from a lordotic curve. These vertebrae carry much of the body’s weight and undergo most of the body’s biomechanical stresses. The pedicles are longer in this area. The spinous processes are more square in shape and horizontal. The intervertebral foramen through which the spinal nerves pass are still relatively large but nerve root compression is more common in this area as compared to the thoracic spine.
