The spine, or backbone, is a long column of bones that runs down the center of a person’s back. It is essential for many functions, such as movement, support, and protecting the spinal cord.

A person’s spine runs from their skull to their pelvis. The spine consists of bones that healthcare professionals call vertebrae.

If a person has an issue with their spine, it may cause pain or limit their mobility. Serious damage to the spine can also damage the spinal cord, which may lead to issues such as numbness or paralysis.

This article discusses the anatomy of the spine in more detail, including its functions, segments, and parts. It also explores common conditions affecting the spine and when someone may consider speaking with a healthcare professional.

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A person’s spine has several important functions. The National Spine Health Foundation (NSHF) notes that some of the spine’s primary functions include:

  • protecting a person’s spinal cord, nerve roots, and internal organs
  • allowing a person to have movement and flexibility
  • providing structural support and balance that allow a person to have an upright posture

The spine consists of five different segments. These segments are responsible for specific functions.

Cervical spine

The cervical spine consists of the first seven vertebrae at the top of the spine. These vertebrae are the smallest in the vertebral column. They are known as C1–C7. People may also refer to C1 as the atlas and C2 as the axis.

This segment of the spine spans from the base of the skull to the upper chest. The vertebrae in the cervical spine make up the bones of the neck.

A person’s cervical spine has a slight curve. This allows the neck to support the weight and movement of a person’s head. It is also flexible, allowing a person to turn their head and neck in many directions.

Thoracic spine

The thoracic spine is the longest segment of a person’s spine. It spans from the upper chest to the middle of the back. There are 12 vertebrae in the thoracic spine, known as T1–T12.

This segment of the spine connects the cervical spine to the lumbar spine. It is also the only part of the spine attached to the rib cage.

The thoracic spine is important for stability. It also helps protect a person’s spinal cord and provides an attachment site for the ribs.

Lumbar spine

A person’s lumbar spine is in the lower back and consists of five vertebrae, known as L1–L5. These vertebrae are the largest bones in the spine.

The lumbar spine supports most of the weight of the upper body. Activities like heavy lifting or sitting down for too long may affect the health of this part of the spine.

The NSHF notes that pain in this region is the most common cause of disability that prevents a person from working as a result of back pain.


The sacrum is the base of a person’s spine. It consists of five vertebrae that fuse to form one bone. These bones, known as S1–S5, fuse together during adolescence.

This segment of the spine connects to a person’s pelvis. It helps transfer an individual’s body weight to the pelvis. This stabilizes the pelvis and helps with walking, standing, and other load-bearing activities.

The sacrum also helps protect the spinal nerves in the lower back.


The coccyx is a small, triangular bone of three to five fused vertebrae. This bone sits below the sacrum. People may also refer to it as the tailbone.

This part of the spine provides an attachment area for different muscles, ligaments, and tendons in the pelvic region. It also helps distribute a person’s body weight while sitting down.

Learn about the difference between tendons and ligaments.

A person’s spine consists of several different parts. Each part plays a different role in helping the spine to function correctly.


The spine consists of 33 vertebrae. These bones contain holes that make up the spinal canal, allowing the spinal cord to pass through them. This helps protect the spinal cord from damage.

The vertebrae of the spine stack on top of each other to form the vertebral column. This column contains three curves, which are the cervical, thoracic, and lumbar spine. These curves allow a person to balance and stand upright.


Doctors call the joints between a person’s vertebrae “facet joints.” These joints allow the spine to move and remain stable.

Each facet joint has a layer of cartilage on its surface. This allows the two bones to slide over each other easily.

A smooth membrane, synovium, also lines the facet joints. This membrane produces a synovial fluid to reduce friction between the joints.


Intervertebral disks are soft, cushioned structures that sit between each vertebrae. These disks act as shock absorbers between the vertebrae. They also allow movement to occur without affecting the stability of the spine.

Disks consist of two parts. The first is a strong, flexible outer cover that medical professionals call the annulus fibrosus. The second is a soft, jelly-like interior called the nucleus pulposus. This part provides the disk with flexibility and strength.

Ligaments and muscles

Ligaments are bands of tough, fibrous tissue that attach bone to bone. Ligaments in the spine help support and stabilize a person’s spine and upper body.

The Arthritis Foundation states there are two main muscle groups that attach to a person’s spine: the flexors and the extensors. The flexors bind to a person’s lumbar spine and allow a person to bend forward. The extensors attach to a person’s spine and allow them to extend it while keeping their back straight.

Spinal cord

A person’s spinal cord is a bundle of nerves that runs through the middle of the spine. It forms the central nervous system along with the brain.

The Arthritis Foundation states that 31 pairs of nerves branch off the spinal cord to other parts of the body. The spinal cord transmits signals from the brain to the rest of a person’s body.

The NSHF outlines common conditions that may affect a person’s spine, including:

The National Institute of Arthritis and Musculoskeletal and Skin Diseases notes that a person could speak with a doctor if they have back pain that does not improve after a few weeks.

Additionally, a person may talk with a doctor if they have back pain alongside:

If a person has severe back pain that does not improve with medication or occurs after a fall or other traumatic injury, it is best to consult a healthcare professional.

The spine is a long column of bones that runs down the center of a person’s back. It consists of 33 vertebrae across different regions of the spine.

A person’s spine helps with stability, structure, and movement. It also helps protect a person’s spinal cord.

People may wish to speak with a doctor if they develop back pain that does not improve in a few weeks. They may also talk with a medical professional if they experience any concerning symptoms alongside the pain, such as difficulty urinating, unintentional weight loss, or weakness in the legs.