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Sasso Family Chiropractic Center |
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ANATOMY OF THE SPINE |
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Table of Contents
IntroductionYour spine is one of the most important parts of your body. It gives your
body structure and support. Without it you could not stand up or keep
yourself upright. It allows you to move about freely and to bend with
flexibility. The spine is also designed to protect your spinal cord. The
spinal cord is a column of nerves that connects your brain to the rest of
your body, allowing you to control your movements. Without a spinal cord you
could not move any part of your body, and your organs could not function.
Keeping your spine healthy is vital if you want to live an active life.
Learn about the spine including: Anatomy
The vertebral body is the large, round portion of bone. Each vertebra
is attached to a bony ring. When the vertebrae are
stacked one on top of the other, the rings create a hollow tube for
the spinal cord to pass through. Each vertebra is held to the others by
groups of ligaments. Ligaments connect bones to bones; tendons connect
muscles to bones. There are also tendons that fasten muscles to the
vertebrae. The bony ring attached to the vertebral body consists of several parts. The laminae extend from the body to cover the spinal canal, which is the hole in the center of the vertebra. The spinous process is the bony portion opposite the body of the vertebra. You feel this part if you run your hand down a person's back. There are two transverse processes (little bony bumps), where the back muscles attach to the vertebrae. The pedicle is a bony projection that connects the laminae to the vertebral body. Between each vertebra is a soft, gel-like cushion, called an intervertebral disc. These flat, round "cushions" act like shock absorbers by helping absorb pressure. The discs prevent the bones from rubbing against each other. Each disc has a strong outer ring of fibers called the annulus, and a soft, jelly-like center called the nucleus pulposus. The annulus is the strongest area of the disc. It helps keep the disc's center intact. The annulus is actually a strong ligament that connects each vertebra together.
The spinal column has real joints (just like the knee, elbow, etc.) called facet joints. The facet joints link the vertebrae together and give them the flexibility to move against each other. The facets are the "bony knobs" that meet between each vertebra. There are two facet joints between each pair of vertebrae, one on each side. They extend and overlap each other to form a joint between the neighboring vertebra facet joint. The facet joints give the spine its flexibility. The facet joints are synovial joints, structures that allow movement between two bones. The ends of the bones that make up a synovial joint are covered with articular cartilage, a slick spongy material that allows the bones to glide against one another without much friction. Synovial fluid inside the joint keeps the joint surfaces lubricated, like oil lubricates the parts of a machine. This fluid is contained inside the joint by the joint capsule, a watertight sac of soft tissue and ligaments that fully surrounds and encloses the joint. The spinal cord branches off into 31 pairs of nerve roots, which exit the spine through small openings on each side of the vertebra called neural foraminae. The two nerve roots in each pair go in opposite directions when traveling through the foraminae. One goes out the left foramina; the other goes out through the right foramina. The nerve root allows nerve signals to travel to and from your brain to the rest of your body.
The spinal cord is a column of millions of nerve fibers that carries messages from your brain to the rest of your body. It extends from the brain to the area between the end of your first lumbar vertebra and top of your second lumbar vertebra. Each vertebra has a hole in the center, so when they stack on top of each other they form a hollow tube (spinal canal) that holds and protects the entire spinal cord and its nerve roots. The spinal cord only goes down to the second lumbar vertebra. Below this level, the spinal canal contains a group of nerve fibers, called the caude equina. This group of nerves goes to the pelvis and lower limbs. A protective membrane, called the dura mater covers the spinal cord. The dura mater forms a watertight sac around the spinal cord and the spinal nerves. Inside this sac, the spinal cord is surrounded by spinal fluid. The nerve fibers in your spinal cord branch off to form pairs of nerve roots that travel through the small openings between your vertebrae. The nerves in each area of the spinal cord connect to specific parts of your body. This is why damage to the spinal cord can cause paralysis in certain areas and not others. It depends on which spinal nerves are affected. The nerves of the cervical spine go to the upper chest and arms. The nerves of the thoracic spine go to the chest and abdomen. The nerves of the lumbar spine reach to the legs, pelvis, bowel, and bladder. These nerves coordinate and control all the body's organs and parts, and allow you to control your muscles. The nerves carry electrical signals back to the brain that allow you to feel sensations. If your body is being hurt in some way, your nerves signal the brain. Damage to the nerves themselves can cause pain, tingling, or numbness in the area where the nerve travels. Without nerve signals, your body would not be able to function.
The muscles next to the spine are called the paraspinal muscles. They support the spine and provide the motor for movement of the spine. Joints allow flexibility, and muscles allow mobility. There are many small muscles in the back. Each controls some part of the total movement between the vertebrae and the rest of the skeleton. These muscles can be directly injured, such as when you have a pulled muscle or muscle strain. They can also cause problems indirectly, such as when they are in spasm after injury to other parts of the spine. A muscle spasm is experienced when your muscle tightens up and will not relax. Spasms usually occur as a reflex (meaning that you cannot control the contraction). When any part of the spine is injured-including a disc, ligament, bone, or muscle-the muscles automatically go into spasm to reduce the motion around the area. This mechanism is designed to protect the injured area. Muscles that are in spasm produce too much lactic acid, a waste product from the chemical reaction inside muscle cells. When muscles contract, the small blood vessels traveling through the muscles are pinched off (like a tube pinched between your thumb and finger), which causes a build up of lactic acid. If the muscle cells cannot relax and too much lactic acid builds up, it causes a painful burning sensation. The muscle relaxes as the blood vessels open up, and the lactic acid is eventually washed away by fresh blood flowing into the muscle.
Doctors sometimes look at a spinal segment to understand and explain how the whole spine works. A spinal segment is made up of two vertebrae attached together by ligaments, with a soft disc separating them. The facet joints fit between the two vertebrae, allowing for movement, and the neural foraminae between the vertebrae allow space for the nerve roots to travel freely from the spinal cord to the body. The spinal segment allows physicians to examine the repeating parts of the spinal column to understand what can go wrong with the various parts of the spine.
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Copyright (C) 2004-2008 by Sasso Family Chiropractic Center. All Rights Reserved. Search Engine Enhancements by JRC Systems
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