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The spine is one of the most important parts of the body and one of the most complex. And if you suffer a back injury, it can be one of the most painful.

“No matter what your age or level of physical activity, it’s important to understand how the spine works,” says Ronald Disimone, MD, orthopaedic surgeon. “You’re less likely to have an injury or recurring back pain if you support your spine with proper movement and posture.”

Here’s an overview of the anatomy of the spine and how the different parts function.

What Is the Spine?

The spine is a series of small bones and connective tissues that support the body and enable movement. It extends from the base of your skull to your tailbone. The spine also includes the spinal cord and the fluid surrounding it.

Other names for the spine are backbone, spinal column, and vertebral column.

What Does the Spine Do?

The spine has many jobs in the human body. Your spine:

• Allows you to stand upright.
• Connects to the ribcage.
• Enables you to stand, walk, twist, and bend.
• Gives your body its flexibility and shape.
• Protects and supports your nervous system, enabling connections between the brain and other parts of your body.
• Transfers the weight of your trunk and abdomen to your legs.

What Are Vertebrae?

Vertebrae are the small bones of the spine. The spine consists of 33 individual vertebrae that stack onto each other like a tower of blocks. There are also two sections of fused vertebrae (the sacrum and coccyx) at the bottom of the spine.

Each vertebra has a hole in the center. When stacked together, the holes form a hollow tube. The spinal cord, which contains bundles of nerves, runs through this tube.

“Because of their jointed structure, the vertebrae allow your spine to rotate and bend,” explains Dr. Disimone. “The only vertebrae that don’t bend are the fused ones at the bottom of the spine.”

Anatomy of the Spine

In addition to vertebrae, the spine has several different components. They include:

Facet joints

These small joints between the vertebrae help your spine move. Like knee or hip joints, they have a cartilage surface. The cartilage is slippery and helps the vertebrae move against each other as your spine rotates.

Facet joints may develop arthritis. Therefore, they can become a source of lower back or neck pain.

Intervertebral discs

These flat, round structures, about half an inch thick, sit between each set of vertebrae. The discs act as shock absorbers, giving the spinal column flexibility and support.

Intervertebral discs consist of two parts. They are:

• Annulus fibrosus — the flexible outer ring of the disc. It has several layers, similar to elastic bands. Because the annulus has many nerve endings, an injury or disc degeneration due to aging can cause considerable pain.
• Nucleus pulposus — the jellylike center of the disc. It’s made partly of water and absorbs shocks.

Whenever you’re standing or moving, your weight moves onto the nucleus. The nucleus then expands, but the annulus holds it in place and maintains the strength of the spine.

Ligaments

These are tough bands of connective tissue that connect your vertebrae. Along with the muscles of the upper body, they provide support and help keep your spinal column in place.

Spinal cord

The spinal cord is the bundle of nerves that starts at the brainstem and goes all the way down the spinal column. Smaller nerves branch out through openings in the vertebrae. These nerves carry messages from the brain into various parts of the body.

Cerebrospinal fluid is a clear, watery substance that cushions the spinal cord. Three protective layers of membrane (the meninges) contain the fluid. The ligaments and bones that surround the spinal cord also help protect its delicate nerves.

What Are the Five Main Parts of the Spine?

You may have heard different names for various parts of the spine. That’s because doctors divide the spine into five main sections. They are:

• Cervical spine (neck) — consists of the first seven vertebrae at the top of the spine. The cervical spine allows you to move your head and neck forward, backward, and side to side. The top of the cervical spine connects to the skull and the bottom to the middle back at shoulder level.
• Thoracic spine (middle back) — the longest, most complex part of the spine consists of 12 vertebrae in the middle of your back. It attaches to your ribs and anchors them in place. It’s less flexible than other parts of the spine.
• Lumbar spine (lower back) — consists of five vertebrae of the lower back. These vertebrae support most of the upper body’s weight and help you lift and carry. The lumbar spine is a common site of injuries from lifting, sitting too long, or wearing the wrong shoes.
• Sacrum (base of the spine) — consists of five vertebrae naturally fused together during adolescence. It’s part of the pelvis, where muscles and ligaments in the hip and pelvic area attach to the spine. Together with the hip bones, it forms the ring known as the pelvic girdle, which helps you stand, walk, and bear weight.
• Coccyx (the tailbone) — this small triangular bone consists of five naturally fused vertebrae. The muscles and ligaments of the pelvic floor attach to the coccyx and help spread out your body weight while sitting. Common injuries to the coccyx include falls and direct blows, which can lead to long-lasting pain and discomfort.

Keeping Your Spine Healthy

“An active lifestyle plays a role in keeping your spine strong and helps you avoid back pain,” stresses Dr. Disimone. “Flexible ligaments and a strong core will help take pressure off your spine and help prevent injuries.”

For a healthy spine:

• Do yoga, Pilates, or other core-strengthening exercises.
• Eat a well-balanced diet with enough calcium and vitamin D.
• Lift heavy objects properly: Keep your back straight, bend at the knees, and use leg strength.
• Maintain a healthy weight.
• Quit smoking.
• Practice good posture.
• Stretch and do resistance training to develop strong, flexible ligaments.
• Try not to sit still for long periods.

Editor's Note: This article was originally published on August 28, 2024, and was last reviewed on September 26, 2024.