11.  X-rays are like light in that they are electromagnetic waves, but they are more energetic so they can penetrate many materials to varying degrees. When the X- rays hit the film, they expose it just as light would. Since bone, fat, muscle, tumours and other masses all absorb X-rays at different levels, the image on the film lets you see different (distinct) structures inside the body because of the different levels of exposure on the film.

14.  Your spine runs the full length of your back. It allows you twist and bend and it holds your bone upright. It also provides protection for the spinal cord, a large bundle of nerves that allows you to transmit information from your brain to the rest of your body.  The Spine is the main structural support of the body. The spine is special because it isn’t made of one or two bones; it’s made of 33 bones in all! These bones are called vertebrae. Each one is shaped like a ring. The vertebrae in the spine are divided into three groups.  The cervical vertebrae in the spine support the head and the neck.  The thoracic vertebrae in the middle of the spine anchor the ribs.  Lumbar vertebrae at the bottom of the spine are the largest and thickest. They provide the most support and stability.  The sacrum and coccyx at the base of the spine is made up of several vertebrae that are fused together.

15. In between each vertebra (the name for just one of these spinal bones) are small cookie shaped disks made of cartilage. These disks keep the vertebrae from rubbing against on another. These also act as the spine’s natural shock absorbers. When you jump, these disks provide the cushioning your vertebrae need to support the force placed on them when you land. Without these disks movement of this kind would be extremely painful. Bending the Spine Together, the 33 vertebrae allow the spine to bend in many directions. It can bend forward and backwards, and from side to side. If the bone was one long bone we would not be flexible at all. Spine curves A healthy spine curves slightly. From the side the spine can be seen to curve slightly forward at the neck, slightly backwards at the chest and slightly forward at the hips.