• Is ring shaped
  
  
• Has no body nor spinous process
  
  
• Has lateral masses instead
  
  
• Superior articular facets are kidney shaped
  
  
• Has anterior and posterior arches bearing a tubercle in the center
  
  
• Posterior arch has a groove on the superior surface. This groove has vertebral arteries and C1.
  
  
• Has an articular surface for the dens on the interior surface of the anterior arch

How does the atlas differ from other cervical vertebrae?
What type of joint is the atlanto-occipital joint?

• Has a tooth like dens/ odontoid process projecting from its body
  
  
• The dens has articular facet for the atlas
  
  
• Short thick bifid spine
  
  
• The vertebral foramen is wide

• Seven in number.
  
  
• The vertebral foramina are large and triangular.
  
  
• The spinous processes are short and bifid except that of the atlas, that is reduced to a tubercle, and that of C7 which is long and non-bifid. The axis has a massive spinous process.
  
  
• The transverse processes are short and perforated.

• Twelve in number.
  
  
• Long spinous procces sloping downwards.
  
  
• Prescence of costal facets.
  
  
• Heart- shaped body.
  
  
• Circular vertebral foramina that become progressively triangular on either end.

• Five in number.
  
  
• Kidney-shaped body.
  
  
• Long, slender horizontal transverse processes.
  
  
• Small triangular vertebral foramina.
  
  
• Large, oblong horizontal spinous processes (short and sturdy).

Sacrum

• Five in number
  
  
• Fused
  
  
• Demarcated by four transverse lines
  
  
• Progressively smaller distally
  
  
• Equidistant sacral foramina on each side

Coccyx

• Four in number
  
  
• Fused into a small triangular bone