The spine is an intricate framework of interlocking bones that, when viewed from the side, form a gentle "S" shape. The spine is a sophisticated system that is very sturdy consisting of muscles, bones, joints, ligaments, discs, a spinal cord, and nerves.
Joints, called "facet joints," and discs allow the spine to bend and twist and absorb mild shocks and bumps. The brain, spinal cord, and nerves manage your body's movement by sending messages to muscles. Supporting the entire structure is an intricate system of ligaments, tendons, and discs.
The vertebrae, facet joints, and discs are vertically stacked in a healthy spine. Ligaments support that alignment. Discs are flexible, spongy pads, that absorb shock between the vertebrae and joints.
The spine has three natural curves, which help to evenly distribute the loads incurred by daily activity—from sitting, walking, and running, to lifting and carrying.
There are three major parts of your spine:
- The cervical spine, or neck
- The thoracic spine, or middle back
- The lumbar spine, or lower back
The sacrum lies at the base of your spine under the fifth lumbar vertebra. The tailbone, or coccyx, is a triangular-shaped bone under the sacrum. The sacrum and the pelvis to form the sacroiliac joints.
The soft tissues that envelop and support your spine make up an intricate network of muscles. With the help of your back muscles, this network helps to keep your body stabilized and upright, and allows it to bend and flex.
The types of muscles that support your spine include:
- Extensors – These are composed of back and gluteal muscles. These muscles help keep your back straight, assist in efforts involving lifting, and moving your thigh away from the body.
- Flexors – These are your abdominal and iliopsoas muscles, which support the spine from the front. They also control the arch of your lower back and move the thigh in toward the body.
- Obliques (also called rotators) – These "side" muscles stabilize your spine when you are standing upright and help rotate your spine and maintain proper posture and spinal curvature.
Your nervous system looks much like electrical wires with millions of cords reaching out to every corner of your body.
Your spinal cord is like a thick braid formed by billions of these nerves. Your body has approximately 15 billion nerve cells—all of which receive and transmit nerve impulses by way of the spinal cord. These impulses control virtually all functions of your body—from your senses to mobility.
Nerve roots and your spinal cord
Your spinal cord actually ends near the base of your middle back, shooting out braids of nerves called "nerve roots." These nerve roots run through a large tunnel-like canal, and at each level of your spinal column, a pair of nerve roots exits from the spine.
Nerve roots are named for the level of your spine they exit from, beginning with a letter and followed by a number. For example, a nerve root in the cervical spine may be called "C6,"while a nerve root in the lumbar region may be called "L4."
A healthy spinal cord allows nerve impulses to flow freely back and forth from the bottom of your feet to your brain. But when your spinal cord becomes misaligned, its parts get out of place and nerves can become pinched. When this happens, the flow of information from your nervous system gets interrupted. This imbalance, called subluxation, can lead to physical problems ranging from minor discomfort to major pain.