The cervical spine is composed of seven vertebrae. The first and second are known as atlas and axis and the others are numbered, such as C3, C4, and so on.
The normal cervical spine should have a concave curve called lordosis when seen from the side.
Viewed from the front or the back, the cervical spine should be vertical or closer to vertical.
The cervical spine is perhaps the most critical area of the spine, as the “upper cervical” portion is where the atlas and axis are found. The atlas is the first vertebra of the spine and the main gate for exit and entrance of information from the brain to the body (nervous system).
The atlas articulates with the head and the second vertebra, the axis, in a different way than the other vertebrae. That joint has no intervertebral disc and is only attached by ligaments.
Also in this same area, the vertebral arteries make a 90º turn to enter up into the brain.
Compression of the vertebral arteries due to misalignment of the cervical spine may cause health problems.