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Question

Difficulty: MediumSupport Structures and Locomotion

A mammalian vertebra features a prominent peg-like odontoid process (dens) projecting from its centrum to articulate with the preceding vertebra, facilitating rotational pivot movement of the skull. Which region or specific vertebra is described?

  1. A
    Atlas vertebra
  2. Axis vertebraAnswer
  3. C
    Thoracic vertebra
  4. D
    Lumbar vertebra

Answer

Axis vertebra
The axis vertebra (second cervical vertebra, C2) is uniquely characterized by the odontoid process (dens), a tooth-like vertical projection rising from its centrum. This projection acts as a pivot axis around which the ring-like atlas vertebra rotates, granting head rotation.

Step-by-Step Solution

1
Identify key anatomical features in the stem
The presence of a peg-like odontoid process (dens) that forms a pivot point for skull rotation.
The odontoid process serves as an axis of rotation between C1 and C2 vertebrae.
2
Compare structural adaptations of cervical vertebrae
The first cervical vertebra (atlas) lacks a centrum and receives the dens, while the second cervical vertebra (axis) bears the dens.
The axis vertebra provides the structural pivot required for horizontal head turning.

Key Concept

Mammalian Axial Skeleton - Cervical Vertebrae Adaptations
Estimated Time:1m 0s
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Topics

Support Structures and Locomotion

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