Question

Atlas vertebra of man is characterised by
A. Procoelous centrum
B. Acoelous centrum
C. Amphicoelous centrum
D. Absence of centrum

Answer 1

Hint: In anatomy, the atlas (C1) is found in the neck and is the highest (first) cervical vertebra of the spine. It is named for the Atlas of Greek mythology because it supports the entire head, just as Atlas supported the globe.

Complete Answer:
- The vertebrae present in the neck area of the body, directly below the skull, are the cervical vertebrae.The vertebrae of the cervix are numbered C1-C7. Highly specialised, the first two, C1 and C2, are assigned specific names: atlas(first cervical vertebra) and axis (second cervical vertebra). The wide anterior middle portion of the vertebra is the centrum.
- The atlas is the topmost vertebra and forms the joint linking the skull and spine with the axis (the vertebra below it). To allow a greater range of motion than normal vertebrae, the atlas and axis are specialised. They are responsible for the head's nodding and rotational motions.
- The atlanto-occipital joint makes it possible for the head on the vertebral column to nod up and down. The dense serves as a pivot that helps, side to side, the atlas and attached head to rotate on the axis. From three centres, the atlas is typically ossified.
- Of these, one occurs during the seventh week of foetal life in each lateral mass and stretches backward; these parts of bone are divided from each other by a small interval filled with cartilage at birth.
- They unite either directly or through the medium of a separate centre produced in the cartilage between the third and fourth years.The anterior arch consists of cartilage at birth; in this, a separate core emerges about the end of the first year after birth, and from the sixth to the eighth year joins the lateral masses.
- The lines of union stretch across the anterior portions of the superior articular facets. There is sometimes no separate center, the anterior arch being created by the two lateral masses' forward extension and ultimate junction; this arch is often ossified from two centers, one on each side of the two lateral masses. Because of its small size, the Atlas vertebra of man is distinguished by the lack of a centrum.

The correct Answer is option (D) Absence of centrum.

Note: A split is referred to as a Jefferson fracture in the first vertebra. In neurodegenerative diseases where altered CSF flow plays a part in the pathological phase, craniocervical junction misalignment is often suspected as a cause.