Question

Odontoid process occurs in
a. Atlas
b. Sacral
c. Axis
d. None of the above

Answer 1

Hint: Odontoid process is present anterior to the spinal cord. It appears as a tooth -like process which is used as a shaft for the rotation of the head. It is present in the second cervical vertebra.

Complete answer:
To solve this question, we must know about the cervical vertebra.
• The cervical vertebra is the vertebra which is present in the neck region below the skull. They are numbered as C1-C7.
• The C1 is known as the atlas vertebra. It is unique as it lacks the vertebral body as well as spinous process. These are circular bones and have two bilateral masses which bear the load.
• The C2 is known as axis. It has tooth-like spinous projections called the odontoid process. It articulates with the anterior arch of the C1 or atlas and forms a joint called the pivot joint. This joint allows the head to rotate. It has vertebral body, laminae and transverse processes which serves as attachment points for muscles.
• Sacral- It is at the bottom of the spine and lies in between the fifth segment of the lumbar spine and the tailbone. It is triangular in shape and has 5 segments(S1-S5) that are fused together.

Hence the correct answer is option (c).

Note: Pivot joint is a kind of synovial joint in which the ends of the two bones join. In the pivot joint, cylinder shaped bone rotates inside another ligament and forms a ring around the joint. This joint is found between axis and atlas which allows the sideward movement of the head.