What is Spine Anatomy?

Made up of vertebrae, facets, discs, nerves, ligaments and muscles, the spine is one of the most complex structures in the body. The spine spans from the top of the neck down to the pelvis. When viewed from the front of the body, normal spinal alignment spans straight from the center of the head to the center of the pelvis. When viewed from the side a slight S-curve, called lordosis, is seen in a healthy spine.

What are the Different Parts of the Spine?

The spine is divided into four major sections:

  • At the top, the cervical spine, or neck, is comprised of 7 vertebrae (C1 – C7). The cervical vertebrae are designed for flexibility and movement. The cervical spine has a backwards “C” shape, known as lordosis.
  • In the middle of the back is the thoracic spine which aids in keeping the body upright. It is comprised of 12 vertebrae (T1 – T12), and has a forward “C” shape, known as kyphosis.
  • In the lower back, or lumbar spine, there are 5 vertebrae (L1 – L5) that are designed for weight bearing loads and movements. Similar to the cervical spine the lumbar spine has a lordosis shape.
  • The sacrum and coccyx make the base of the spine. The sacrum is made of five fused vertebrae that form a single bone and the coccyx is made of 3 fused vertebrae. Similar to the thoracic spine, the sacrum has a kyphosis shape.

What Causes the Natural Curve in the Spine?

The natural curve of the spine originates from the shape of the discs and the shape of the vertebral bodies. The natural curves of the spine are designed to promote movement, balance and stability. The curves are essential to upright posture and ease of movement. The spinal curve is designed to help absorb impact on movement of the body.

The spine has two alternating curves to create an “S” like shape. In the cervical and lumbar spine there is normally an inward curvature or a backwards “C” shape known as lordosis. In the thoracic spine and sacrum there is an outward curvature known has kyphosis or a forward “C” shape. In a healthy spine, these curves balance each other so that when the patient stands they are well balanced with their head straight above their hips when viewed from the side.

How are Vertebrate Classified?

The human spine is made up of 33 vertebrae bones. The vertebrae are irregular bones that are in a classified based on location:

  • Cervical spine (C1 – C7)
  • Thoracic spine (T1 – T12)
  • Lumbar spine (L1 – L5)

As the building blocks of the spine, the vertebrae, facets, and the discs combine to create the natural curve of the spine. For the lumbar and cervical spine, stacking the vertebrae one on top of the other would create a straight column, but the angular shape of the discs is what creates the normal curve in these sections. For the thoracic spine, it is the unique shapes of the vertebrae along with the discs that help create the normal curvature of this section.   

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What Part of the Spine is Most Commonly Injured?

The lumbar spine, or lower back, is the most common area injured. This section of the spine sustains the greatest strain on the back with the least structural support. The cervical spine, or neck area, is also more susceptible due to lower structural support. The thoracic spine is the least susceptible as it is connected to the rib cage structure and is well supported by the extra structures.