Backbone
The spine refers to the bone of the back. Because one bone is made in the part called the vertebral body, the gathering is called means spine.
The spine is comprised of seven cervical vertebrae, 12 thoracic vertebras, five lumbar vertebrae and sacral vertebrae, root of a tail from the head.
The cervical vertebrae draw an arc gently towards the front as you see in a figure, and the thoracic vertebra draws an arc towards the back and the lumbar vertebrae gently towards the front again.

In this figure, turns of L1, L2, L3, L4, L5, are attached from the direction of the head for the bone of the waist (lumbar vertebrae).

Reference：http://www.nsknet.or.jp/~takaokun/spine.html
Vertical dissection is shown at the place which looked at the waist from the side

There is the intervertebral disc of impact-absorbing equipment between the bones (lumbar vertebrae) of the waist.

A pipe called a spinal canal is behind the centrum of a lumbar vertebrae, and the nerve called the spinal cord passes along the inside of this.

(Cautions: In a lumbar vertebrae part, a spinal cord becomes a cauda-equina nerve below the 1st lumbar vertebrae in general.  A cauda-equina nerve is because it is like the tail of a horse literally.)

The nervous branch has come out from the spinal cord and this is called nerve root.

The nerve root extends obliquely downward of the body.
It is determined which part of the foot each lumbar vertebrae nerve root grows on.

Spinal Cord

 The spinal cord is surrounded by spine.

Let’s look at by animation.

Seeing the spine from the side, we can see a bone of the spine first.
Furthermore, if it goes to center of the body, the spinal cord shown with black is visible.
The spinal cord is just at the center of the spine, and it becomes cerebrum in the direction of the head

That is, the spinal cord is the one that a cerebrum is extended to a leg.
It becomes the black line around the waist.
Although the spinal cord comes to the end around the first bone of the waist (lumbar vertebrae), a nerve is taken out from there like the tail of a horse toward the bottom.
This is shown with the black line.

This photograph expresses lower 1/3 of the head from the area of the neck with the one which is photographed by MRI (magnetic resonance imaging). The spine is watched from the side like the animation. When it moves to the center of the spine, it is the spinal cord which is projected black. Spinal cord grows towards a head and becomes a cerebral part named medulla oblongata and the bridge

The one looking white around the spinal cord is cerebrospinal fluid. It is a liquid such as so-called water. Since our brain and spinal cord are soft like tofu, they hit skull and a wound may be made.
Therefore it floats in cerebrospinal fluid in the same way as the tofu which floats in water not to make a wound.