The spinal column is made up of 33 vertebrae organized into five distinct sections: cervical, thoracic, lumbar, sacrum, and coccyx. These sections run from the base of your skull to your tailbone, each with a different shape, size, and job. Together they protect the spinal cord, support your body weight, and allow you to bend and twist.
Cervical Spine: The Neck
The cervical spine sits at the very top and contains seven vertebrae, labeled C1 through C7. These are the smallest and most mobile vertebrae in the entire column. The top two have special names and unique shapes: C1 (the atlas) cradles your skull and lets you nod your head up and down, while C2 (the axis) has a bony peg that allows your head to rotate side to side.
Eight pairs of cervical nerves branch out from this region. They control sensation and movement in your head, neck, shoulders, arms, and hands. A pinched nerve here, called cervical radiculopathy, can send pain, tingling, or weakness shooting down one arm. Cervical spondylosis, the gradual wear of the discs and joints in this area, is one of the most common age-related spine conditions and affects a large percentage of people over 60.
The cervical spine has a gentle inward curve called a lordotic curve. This forward arc helps balance the weight of your head, which averages about 10 to 12 pounds, over your center of gravity.
Thoracic Spine: The Middle Back
Below the cervical region, 12 thoracic vertebrae (T1 through T12) make up the longest section of the spine. Each of these vertebrae connects to a pair of ribs, forming the bony cage that shields your heart and lungs. That rib attachment is exactly why the thoracic spine is the least mobile section. You can’t bend or twist your mid-back nearly as much as your neck or lower back.
The thoracic spine curves gently outward, creating a rounded shape called a kyphotic curve. When this rounding becomes exaggerated, the condition is known as kyphosis, sometimes called a “hunchback” posture. It can result from osteoporosis, poor posture, or age-related disc changes.
Twelve pairs of thoracic nerves exit this region. They supply the muscles between your ribs, the skin of your chest and upper abdomen, and they play a role in the autonomic nervous system, helping regulate organs like the heart, lungs, and digestive tract through connections in the lateral part of the spinal cord.
Lumbar Spine: The Lower Back
Five vertebrae (L1 through L5) form the lumbar spine, and they are the largest in the entire column. That size is no accident. The lumbar region carries the bulk of your upper body weight and transfers those forces downward into the pelvis. The discs between lumbar vertebrae act as shock absorbers: a gel-like center creates internal pressure that pushes outward against tough, layered outer rings, slowing the transmission of force from one vertebra to the next. Even at rest, these discs maintain a baseline level of internal pressure, keeping them ready to handle sudden loads.
This combination of heavy load-bearing and wide range of motion makes the lumbar spine the most common site of back pain. Disc herniations here can press on the nerves that travel into your legs, producing the sharp, radiating pain often called sciatica. Lumbar spondylosis, the breakdown of joints and discs in this area, is another frequent source of stiffness and discomfort.
Like the cervical spine, the lumbar region curves inward (lordotic curve). An exaggerated version of this curve tilts the pelvis forward and is called lumbar lordosis. Five pairs of lumbar nerves exit here, controlling sensation and movement in the hips, thighs, knees, and parts of the lower legs.
Sacrum: The Base of the Spine
The sacrum is a large, triangle-shaped bone wedged between the two halves of your pelvis. It starts as five separate vertebrae (S1 through S5) but fuses into a single solid structure. This fusion begins during fetal development and continues gradually, with full ossification and fusion of all sacral elements completing by around age 30.
Because it locks into the pelvis at the sacroiliac joints on each side, the sacrum acts as the keystone of the entire spinal column. Every pound of force generated by your upper body during walking, lifting, or sitting passes through the lumbar spine and into the sacrum, which distributes it across both hip bones and down into your legs. Five pairs of sacral nerves pass through openings in the bone. These nerves serve the pelvic organs, buttocks, backs of the thighs, and much of the lower leg and foot. They also contribute to bladder and bowel control.
Coccyx: The Tailbone
At the very bottom of the spine, four small vertebrae fuse together to form the coccyx, commonly called the tailbone. It is the remnant of a tail structure found in earlier stages of human evolution. Despite its small size, the coccyx serves as an anchor point for muscles, tendons, and ligaments of the pelvic floor. These tissues support the organs in your lower abdomen and play a role in bowel control and stability when you sit.
A single pair of coccygeal nerves exits from this region. Tailbone pain, called coccydynia, most often results from a fall, prolonged sitting on hard surfaces, or childbirth. It typically feels worse when you sit down or stand up from a seated position.
How the Sections Work Together
The alternating curves of the spine are central to how these five sections function as a unit. The cervical and lumbar regions curve inward, while the thoracic spine and sacrum curve outward. This S-shaped arrangement distributes mechanical stress more evenly than a straight column would, acting like a spring that absorbs impact during walking and running.
In total, 31 pairs of spinal nerves exit the column: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Each pair maps to a specific strip of skin called a dermatome and a specific group of muscles. This is why doctors can often pinpoint which level of the spine is affected based on where you feel numbness, tingling, or weakness. Pain radiating to the outside of your forearm, for example, points to a different cervical nerve than pain in your pinky finger.
Vertebrae also change in size and shape from top to bottom. Cervical vertebrae are small and have special openings on each side that protect blood vessels traveling to the brain. Thoracic vertebrae have flat surfaces where the ribs attach. Lumbar vertebrae are the widest and thickest, built to handle compression. The sacrum and coccyx sacrifice all mobility for structural stability, fusing into solid bone to anchor the spine to the pelvis.