Spine Anatomy and Associated Conditions

Function of the Spine A healthy spine is arranged in three natural curves forming an "S" shape that maintains the structure of the trunk. These curves keep your body in balance as you move and help to distribute your weight evenly throughout the spine. The spine also serves as an attachment for strong, flexible muscles that help support your body, and acts as protection to the spinal cord and its exiting nerves.

Bones -- 24 moving Vertebrae

7 Cervical Vertebrae
12 Thoracic Vertebrae
5 Lumbar Vertebrae
Sacrum -- 5 fused Vertebrae
Coccyx -- Tailbone

Discs
The discs in the spine separate the vertebrae and are made up of

Annulus -- Outer rings of cartilage type material protecting the nucleus.
Nucleus - Jelly-type material that makes up inner part of disc Mostly made up of water with a cushioning material that acts like a shock absorber for the spine.
Disc Herniation occurs when a portion of the disc (the nucleus of the disc) ruptures, protrudes or tears through the annulus and causes pressure on the nerves that exit each level of the spine.

Joint/Facets
These are the small joints of the spine that allow two different vertebral bodies to perform flexion/extension, side bending and rotation of the spine. Facet joints are located on the back portion of the vertebral bodies and are designed to protect the vertebral bodies from too much movement in a particular direction.

Foramen
Foramen are the openings between the vertebral bodies which allow nerves to exit at each level of the spine. Narrowing of the foramen by extra bone growth or ligament thickening is know as spinal stenosis, which can entrap a nerve as it exits the spine. Movements affect the size of the foraminal opening, which may increase or decrease the symptoms of spinal stenosis. For instance, forward bending increases the opening for the exiting nerve, and conversely, backward bending, or extension, decreases the space.

Ligaments
Ligaments are supportive bands of tissue that run the entire length of the spine in the front and the rear of the spine that help with the stability of the spine. There are also ligaments at each joint of the spine that help limit rotational movements as well as flexion and extension of the spine. Ligaments can be stretched or torn by excessive or forceful movement, which can lead to spinal stability problems.

Muscles
Strong flexible muscles are critical in the maintenance of a healthy spine. Small muscles actually move each vertebral level. Other spinal muscles run the length of the spine in the back and support spinal extension. Larger muscle groups that also have an effect on the function of the spine include the abdominal, hip and leg muscles.