Why Backs go Bad: the Discs
Located between the individual vertebrae are discs (intervertebral discs), which serve as shock absorbers or cushions between the bones. The disc is cubed or brick shaped, similar in size and shape to the body of the vertebrae, which they lie between along the spine. Unlike the vertebrae, they are more flexible, and they have an ability to flatten when the force of gravity are applied to it, and to resume their cube or brick shape when we are lying down. Each disc (intervertebral disc) is composed of two layers or sections: the outer cover called the annulus fibrosis and a "gel-like inner substance" called the nucleus pulposis. This gel filling (nucleus pulposus) is composed of water, collagen fibrils, chondrocytes, and proteoglycan aggrecans with ends that attach water, hyaluronic long chains, keratin sulfate, and chondroitin sulfate.
The discs aren't supplied with nutrients the way tissues and organs are from blood vessels and cerebrospinal fluid. The discs are supplied with water and nutrients by absorbing fluid from the adjacent muscles and tissues. Your intervertebral discs absorb water and fluid when you are lying down. As soon as you sit up , stand, or walk, the force of gravity begins to push the discs and vertebral bone together, compressing the discs and squeezing some of the fluids out of them. Actually, after a normal day, you can lose an overall inch in total height by the end of the day as a result of a compression of the discs.
Sections of the Spine: Though there is really is no actual physical boundary between one section of the spine to another, it is often described as if it were five separate units. The sections of the spine correspond to the part of the body that they are located in and separated into groups according to their curve.
The cervical spine includes the first 7 vertebrae and begins at the base of the spine. The first two vertebrae, the atlas and axis, are the most physically different from the other vertebrae. The cervical spine is also known as your upper back. The atlas and axis have little or no body and are more ring-like and flat. The cervical spine begin at the base of your brain and are involved in controlling in feeling and movements of your head, shoulders, and arms. Beginning at the back of your head, the cervical spine curves backwards towards the front of your body.
The curve of your spine then bends towards the back of your body, beginning at the first of your 12 vertebrae of your thoracic spine. The thoracic spine, also known as your middle back, supplies sensations and information and movement to your skin and organs and other structures in your chest, and upper body.
The lumbar spine, or lower back, is composed of the five largest vertebrae of your back. These lumbar vertebrae are the largest because they, along with the lumbar discs, have to absorb the most weight. These lumbar vertebrae have to withstand a lot of compression as a result of gravity. When a patient experiences lower back pain, it this area of the back that is most often affected.
The sacrum, consists of 5 vertebrae that are fused together by the time we reach physical maturity.
Located below the sacrum is the coccyx (tailbone), which is a structure composed of 4 fused vertebrae.
Next, let's take a look at the spinal cord and why backs go bad.