The spinal column is made up of 24 stacked and movable bones, called vertebrae, and the sacrum and coccyx that connect the spine to the pelvis.
The spinal column is made up of four main segments:
For detailed information about the spine, view this video:
The first seven vertebrae (C1-C7), starting just below the skull, make up your cervical spine. The cervical spine supports the weight of your head and offers protection to the nerves that connect the brain to the rest of your body. Though the vertebrae making up the cervical spine are small, they are more flexible then the rest of the spine and allow movement of the neck and head in all directions.
The cervical spine is at risk for injuries due to smaller bones, discs, facet joints, and muscles bearing the weight and support of the head (11-15 pounds).
The thoracic spine consists of the 12 vertebrae (T1-12) located below the cervical spine (neck) and above the lumbar spine.
These vertebrae connect each of your ribs and the back wall of the thorax (chest) to the spine offering stability and protection for vital organs including heart, liver, and lungs. Because the thoracic spine is anchored to the rib cage, it has less flexibility than the rest of the spine.
The intervertebral discs and spinal canal are thinner and narrower in the thoracic spine than in the cervical and lumbar spine, adding to its inflexibility.
The lumbar spine is made up of the bottom five vertebrae (L1-L5), ending at the base of the spine, the sacrum, and connecting to the pelvis.
The vertebrae and spinal canal in the lumbar spine are the largest of the three spinal segments and support entire weight of the torso.
The lumbar spine is capable of power and flexibility, specifically where the vertebrae meet the sacrum allowing rotation of the pelvis and hips. Because of the weight and joint rotation movement the lumbar spine incurs, injury to this segment of the spine is the most common.
The sacrum is made up of 5 vertebrae which fuse into one solid bone by early adulthood. The coccyx forms at the lower end of the sacrum and acts as an attachment point for one end of the pelvic floor muscles, which control bowel and bladder function.
The sacrum is flanked on both sides to the hip bones (ilium), creating a left and right sacroiliac joint. In early childhood, this joint gradually develops an irregular surface topography and very strong ligaments that together provide stability and limit motion.
Hormones during pregnancy cause these ligaments to stretch so that the pelvic ring can open wider and allow the fetus to descend.
The sacroiliac joints often have very limited motion, or even fuse together, in late adulthood.