What Is The Spine?

Definition: Stacked on top of one another in the spine are more than 30 bones, the vertebrae, which together form the spine.

They are divided into four regions:

• seven cervical or neck vertebrae (labeled C1-C7)


• twelve thoracic or upper back vertebrae (labeled T1-T12)


• five lumbar vertebrae (labeled L1-L5)
(the lower back)

• the sacrum and coccyx (fused bones at the base of the spine)
  

Vertebrae are linked by ligaments, tendons, and muscles.

Back pain can occur when, for example, someone lifts something too heavy, causing a sprain, pull, strain, or spasm in one of these muscles or ligaments in the back.

Between the vertebrae are round, spongy pads of cartilage called discs that act like shock absorbers.

Degeneration or pressure from overexertion can cause a disc to shift or protrude and bulge, causing pressure on a nerve and resultant pain. When this happens, the condition is called a slipped, bulging, herniated, or ruptured disc, it sometimes results in permanent nerve damage.

The column-like spinal cord is divided into segments similar to the corresponding vertebrae:

• cervical
• thoracic
• lumbar
• sacral
• coccygeal

The cord also has nerve roots and rootlets which form branch-like appendages. Along the dorsal root are the cells of the dorsal root ganglia, critical in the transmission of "pain" messages from the cord to the brain. Here is where injury, damage, and trauma become pain.

Related Resources

Guide To Lower Back Pain

Back Pain Quiz

_{Source: NIH Publication No. 01-2406}