Anatomy 101

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The spine is one of the most important parts our body. It has three main functions:

  • Protects the spinal cord
  • Gives the body structure and support
  • Allows us to move freely

The Bones and Joints

The spine is made of 33 bones called vertebra that are stacked one above each other. There are:

  • 7 cervical vertebras in the neck
  • 12 thoracic vertebra in the middle back
  • 5 lumbar vertebras in the low back.

The sacrum is a wedged shaped bone in the pelvis made of 5 fused verterbra. The tail end of the spine (literally) we have the coccyx made of 4 fused coccygeal vertebras. The vertebras are given names based on their position in the spine. L1 is the first lumbar vertebra. There are 2 bones that have special names because of their special function. The atlas (C1) holds up the head and the axis allows the head to rotate from side to side.

2vertebra

Here you can see 2 vertebra stacked on top of the other. 3 joints join the vertebras to each other. The large disc in the front is like a soft cushion and provides support and absorbs pressure. The disc has a poor blood supply and receives its nutrition via sucking the nutrients from the body when you move. Behind the disc there are 2 facet joints. The facet joints guide the movement of the vertebra and have a large supply of nerves that feed your brain with information about where your spine is and how it is moving. Your brain uses this information when it is deciding how your organs should function. Some amazing research by Dr. Akio Sato has been done in this field. This is why is it is so important to maintain the normal movement of your spine. Between the facet joints and the disc is a gap called the intervertebral foramen or the IVF for short. The spinal nerves exit the spinal canal through the IVF. There are a number of bumps on each vertebra. You can see the transverse and spinouts processes in the picture. The muscles and ligaments of the spine attach to these bumps.

The Ligaments

There are a number of ligaments that cross between two vertebras. The ligaments hold the bones together while still allowing the joints to move. Some of the ligaments cross the intervetebral foramen and reduce the space the spinal nerves have to exit the spinal canal. When there is joint restriction the ligaments can rub twist and squash the nerves reducing their ability to carry healthy information from the brain to the body or the body back to the brain. With age and lack of exercise the ligaments become shorter and harder, making the joints stiffer. In the long term tight and stiff ligaments pull on the bones and produce bone spurs. Exercise and adjustments to maximize the health of the ligaments will minimize the effects of osteoarthritis in the future.

The Muscles

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here are multiple layers of muscles in the back. Some are for supporting our spine and are called postural muscles or core muscles others are for moving our spine and are called the prime movers. The muscles are arranged in different patterns to bend our spine forwards backwards, sideways and rotate to each side. Like all muscles of the body the spinal muscles require good exercise and stretching to maintain their health and the health of your spine.

The Nerves

The Spinal CordThe spinal cord is the information superhighway between your brain and your body. Without it you could not move any part of your body and your organs could not function. It is made of millions of nerves. The spinal cord is protected by the bony spinal canal formed by the vertebra that are stacked one on top of the other. It is also protected by the dura mater, a tough covering around the cord. Between the dura mater and the spinal cord is the cerebrospinal fluid (CSF) The CSF is important for protection of the central nervous system (CNS), which includes the brain and the spinal cord and feeds the CNS with nutrients from the blood.

The Peripheral Nerves

The spinal nerves convey information between the central nervous system and the rest of the body. The spinal nerves exit the spinal canal through each of the intervertebral foramen between each pair of vertebra. Like the tributaries of a river the small spinal nerves form larger nerves, such as the sciatic nerve, which runs down the buttock into the leg. This is how your brain controls every single cell and organ in you body. The following chart describes which spinal nerves innervate (supply) which parts of the body. You will notice that all the body parts actually receive information from more than one spinal nerve and the nerves travel a great distance to get to the organ they are supplying. This is why the actual problem in the spinal can be a long way away from you feeling the problem.