anatomy of the back

three parts of human spine

If you want to feel confident about treating your own problem, you must be armed with some simple information about the anatomy of the back. It's important to know how your back works when it works well.  


1. As the central strut of your skeleton so that you can hold your head up and move your arms and legs 

2. As a bendable pillar allowing you to position the upper thinking-and-working part of your body – the head and hands - at purposeful heights

3. To provide a protective bony casing for the delicate spinal cord and its branching off spinal nerves

Posture is important to the working anatomy of the back!

With a ideal posture, the spine exhibits an elongated ‘S’ bend (when viewed from the side) from top to bottom. This insures that equal weight is borne fore and aft of the line of gravity so that you can balance easily as you stand.  It also works more dynamically in absorbing impact like a spring, literally sinking and springing with every step. This prevents jarring throughout the spine, while also giving your brain as jangle-free an existence as possible. 

The spine is divided into 7 cervical, 12 thoracic and 5 lumbar vertebrae.  Each spinal segment must contribute to overall spinal movement by tilting, swivelling and gliding equally in both directions on its neighbour below. Each vertebra must have full use all these six degrees of freedom. 

Confused about your back and what's causing the pain after seeing yet another spinal specialist? Download Sarah's video here explaining about the different causes of back pain and what you can do about it. 

The 3 critical components parts of spinal anatomy:
the intervertebral discs, the facet joints & the spinal nerves

Most of the weight through the spine is carried through the vertebral bodies at the front of the spine, separated by the intervertebral discs. A disc is like a pressurised sack that thrusts the vertebrae apart while at the same time glueing them together. The higher the water content of the intervertebral disc the better the shock absorption and the more free-flowing the movement of its vertebrae above and below.

Deficiencies in segmental movement cause small problems from which bigger problems can flow. See the page micro trauma of the disc wall.

The intervertebral disc is made up of central bauble of fluid called the nucleus surrounded by a multi-layered mesh disc wall call the annulus. The disc is the largest avascular structure in the body – meaning it has virtually no blood supply, except for the very outer periphery  (see above). Only this part of the disc carries a nerve supply. 

The facet joints at the back of the spine hook the segments together and control movement so that the segments don't topple off one another when the spine moves. Unlike the intervertebral discs however, facets bear very little weight. Similarly unlike the discs, the facet joints are very bloody and have very rich nerve supply. 

Paired spinal nerves branch off the spinal cord and thread out of the spine between adjacent vertebrae at each spinal level. It is important to note that inflammatory changes of the facet joint and the intervertebral disc can cause spinal pain. Degenerative changes of both the structures can also irritate the spinal nerve as it squeezes past. This is called sciatica in the leg and brachialgia in the arm. 

Other Anatomy Pages

Understanding the way the ribs slot into the spine is key to understanding and treating upper back pain. See Anatomy of the Ribcage.

The superficial and deep back muscles have different qualities and perform different roles. Those differences become more marked in the presence of chronic low back pain. Read about Back Muscles Anatomy

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