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Difficulty: MediumSupport Structures and Locomotion

A specimen of a mammalian vertebra observed in the laboratory features a massive, thick centrum, a broad neural spine, and long, forward-pointing transverse processes, but lacks both rib facets and vertebrarterial canals. Which region of the vertebral column does this vertebra belong to?

  1. Lumbar region, adapted for bearing heavy body weight and supporting abdominal muscle attachmentAnswer
  2. B
    Thoracic region, adapted for articulating with ribs to form the protective chest cage
  3. C
    Cervical region, adapted for protecting vertebral blood vessels leading to the brain
  4. D
    Sacral region, adapted for fusion into a rigid structure that articulates with the pelvic girdle

Answer

Lumbar region, adapted for bearing heavy body weight and supporting abdominal muscle attachment
The lumbar region contains vertebrae with the largest, most massive centra to support the weight of the upper body. They feature long, well-developed transverse processes pointing anteriorly for the attachment of powerful trunk and abdominal muscles, and they lack both rib facets (found only in thoracic vertebrae) and vertebrarterial canals (found in cervical vertebrae).

Step-by-Step Solution

1
Analyze the structural features described in the stem.
Identified key features: massive/thick centrum, long forward-directed transverse processes, absence of rib facets, and absence of vertebrarterial canals.
Each region of the mammalian vertebral column has specific morphological adaptations corresponding to its anatomical location and functional role.
2
Rule out cervical and thoracic regions based on absent diagnostic features.
Absence of vertebrarterial canals excludes cervical vertebrae; absence of rib facets excludes thoracic vertebrae.
Vertebrarterial canals passage vertebral arteries in cervical vertebrae, while rib facets are exclusive to thoracic vertebrae.
3
Match the specimen features with the correct vertebral region.
The presence of a massive centrum and prominent transverse processes without rib/canal features is characteristic of lumbar vertebrae.
Lumbar vertebrae bear the largest gravitational weight of the trunk, requiring a sturdy centrum and large processes for powerful back and abdominal muscle attachment.

Key Concept

Mammalian Vertebral Structural Adaptations
Estimated Time:1m 0s
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Topics

Support Structures and Locomotion

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