What Is Lumbar & Thoracic Spine?
The human spine is divided into five major regions: cervical, thoracic, lumbar, sacrum and coccyx. The spine protects the spinal cord and exiting peripheral nerves, and provides attachment points for the extremity bones and ribs.
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Thoracic Spine Anatomy
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The thoracic spine is composed of 12 bones called "vertebrae." The thoracic vertebrae increase in size from the top thoracic vertebrae (T1) through the bottom thoracic vertebrae (T12). Each vertebrae is separated from its neighbors by cartilaginous discs that absorb shock and allow movement.
Thoracic Spine Rib Attachments
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The unique feature of the thoracic spine is the presence of ribs attaching to the vertebrae. The sides of each vertebra have projections, called "transverse processes," on them to which the ribs attach. These ribs protect the vital organs in the chest such as the heart and lungs, and they add strength and support to the thoracic spine. Because of the rib attachments, the thoracic spine is very stable, but it is also more immobile than the rest of the spine.
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Thoracic Spine Range of Motion
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The rib attachments limit the range of motion for the thoracic spine. The most motion is in the form of flexion and extension (forward and backward bending).
Lumbar Spine Anatomy
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The lumbar spine is composed of five vertebrae. Like the thoracic spine, the lumbar vertebrae increase in size from top to bottom (L1 to L5) and are separated by shock-absorbing discs. The lumbar spine vertebrae are much larger, thicker, and stronger than thoracic vertebrae because their main function is to bear the body's weight.
Lumbar Spine Range of Motion
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Because there are no bony attachments to the lumbar vertebrae, they are free to move in multiple directions. The lumbar vertebrae allow twisting, forward bending, backward bending and side bending motions. The trade-off for this increased range of motion is less stability than the thoracic spine, as most of the support and stability comes from muscles and ligaments.
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