Your Spine
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Your spine is very important to your overall wellbeing. It is essential that we take care of our spines. Learn more about your spine and how it functions.
Vertebrae
The individual bones of the spine are the vertebrae. These are the building blocks of the spinal column. The vertebrae protect and support the spinal cord. They also bear the majority of the weight put upon your spine. The body of each vertebra is the large, round portion of bone. The body of each vertebra is attached to a bony ring. When the vertebrae are stacked one on top of the other, this ring creates a hollow tube where the spinal cord passes through.
The bony ring attached to the vertebral body consists of several parts. First, the laminae extend from the body to cover the spinal canal, which is the hole in the center of the vertebrae. Second, 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. Then there are two transverse processes (little bony bumps), where the back muscles attach to the vertebrae. Finally, the pedicle is a bony projection that connects to both sides of the lamina.
The vertebra, like all bones, has an outer shell called cortical bone that is hard and strong. The inside is made of a soft, spongy type of bone that is called cancellous bone. |
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Intervertebral Disc
The intervertebral discs are flat, round "cushions" that act as shock absorbers between each vertebra in your spine. There is one disc between each vertebra. 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 disc's outer layer and the strongest area of the disc. It also helps keep the disc's center intact. The annulus is actually a strong ligament that connects each vertebra together.
The mushy nucleus of the disc serves as the main shock absorber. The nucleus is made up of tissue that is very moist because it has high water content. The water content helps the disc act like a shock absorber - somewhat like a waterbed mattress. |
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Facet Joint
The facets are the "bony knobs" that meet between each vertebra to form the facet joints that join your vertebrae together. There are two facet joints between each pair of vertebra, one on each side. They extend and overlap each other to form a joint between the neighboring vertebra facet joints. Without the facet joints, you would not have flexibility in your spine, and you could only move in very straight and stiff motions.
The facet joints are what are known as synovial joints. A synovial joint, such as the knee or elbow, is a structure that allows movement between two bones. In a synovial joint, the ends of the bones are covered with a material called articular cartilage. This material is a slick spongy material that allows the bones to glide against one another without much friction. |
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Spinal Regions
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The spine itself has three main segments - the lumbar, thoracic, and cervical spines. We also include the sacrum in our discussion. Let's learn about each of these in greater detail.
Cervical Spine
The cervical spine is made up of the first seven vertebrae in the spine. It starts just below the skull and ends just above the thoracic spine. The cervical spine has a lordotic curve (a backward "C"-shape) - just like the lumbar spine. The cervical spine is much more mobile than both of the other spinal regions - think about all the directions and angles you can turn your neck.
Unlike the rest of the spine, there are special openings in each vertebra in the cervical spine for the arteries (blood vessels that carry blood away from the heart), as well as the spinal canal that carries the spinal cord. The arteries that run through these openings bring blood to the brain.
Two vertebrae in the cervical spine, the atlas and the axis, differ from the other vertebrae because they are designed specifically for rotation. These two vertebrae are what allow your neck to rotate in so many directions, including looking to the side.
The atlas is the first cervical vertebra - the one that sits between the skull and the rest of spine. The atlas does not have a vertebral body, but does have a thick forward (anterior) arch and a thin back (posterior) arch, with two prominent sideways masses.
The atlas sits on top of the second cervical vertebra - the axis. The axis has a bony knob called the odontoid process that sticks up through the hole in the atlas. It is this special arrangement that allows the head to turn from side to side as far as it can. Special ligaments between these two vertebrae allow a great deal of rotation to occur between the two bones.
Though the cervical spine is very flexible, it is also very much at risk for injury from strong, sudden movements, such as whiplash-type injuries. This high risk of harm is due to: the limited muscle support that exists in the cervical area, and because this part of the spine has to support the weight of the head. This is a lot of weight for a small, thin set of bones and soft tissues to bear. Therefore, sudden, strong head movement can cause damage. The nerves of the cervical spine go to the upper chest and arms. |
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Thoracic Spine
The thoracic spine is made up of the middle 12 vertebra of the spine. These vertebrae connect to your ribs and form part of the back wall of the thorax (the ribcage area between the neck and the diaphragm). This part of the spine has very narrow, thin intervertebral discs, so there is much less movement allowed between vertebrae than in the lumbar or cervical parts of the spine. It also has less space in the spinal canal for the nerves. The thoracic spine's curve is called kyphotic because of its shape, which is a regular "C"-shaped curve with the opening of the "C" in the front.
The nerves in your thoracic spine go to your chest and abdomen.
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Lumbar Spine
The lowest part of the spine is called the lumbar spine. This area has five vertebrae. The lumbar spine's shape has what is called a lordotic curve. The lordotic shape is like a backwards "C". If you think of the spine as having an "S"-like shape, the lumbar region would be the bottom of the "S". The vertebrae in the lumbar spine area are the largest of the entire spine, so the lumbar spinal canal is larger than in the cervical or thoracic parts of the spine. Because of its size, the lumbar spine has more space for the nerves to move about.
Low back pain is a very common complaint for a simple reason. Since the lumbar spine is connected to your pelvis, this is where most of your weight bearing and body movement takes place. Typically, this is where people tend to place too much pressure, such as: lifting up a heavy box, twisting to move a heavy load, or carrying a heavy object. Such repetitive injuries can lead to damage to the parts of the lumbar spine.
The nerves of the lumbar spine then reach to your legs, bowel, and bladder. |
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Sacrum
Below the lumbar spine is the sacrum. The sacrum is actually a group of specialized vertebrae that connects the spine to the pelvis. During development (those nine months before birth), these vertebrae grow together or fuse creating one large "specialized" vertebral bone that forms the base of your spine and center of your pelvis.
Sometimes people are born with a sixth vertebra in the lumbar region called a transitional (or sixth) vertebra. In these cases, the sacrum forms as a vertebra rather than part of the fused sacrum. This occurrence is not dangerous and does not appear to have any serious side effects.
The nerves that leave the spine in the sacral region control the bowel and bladder functions and give sensation (feeling) to the crotch area. |
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