In quadrupeds, which region has the largest vertebral canal?

In quadrupeds, which region has the largest vertebral canal?

• A. Thoracic
• B. Lumbar
• C. Sacral
• D. Cervical

Answer: (D)

The vertebral canal size along the spine reflects how much neural tissue sits in each region. In quadrupeds, the cervical region contains the cervical enlargement, which supplies nerves to the forelimbs, so the spinal cord is thickest there. To accommodate this thicker cord (and the brainstem just above it), the vertebral canal in the cervical region is the widest. The thoracic region is tighter because of the rib attachments, and the sacral region is relatively narrow due to the fused sacral bones. Although there is a lumbar enlargement for the hindlimbs, its canal isn’t as large as the cervical one. So the cervical region has the largest vertebral canal.

The vertebral canal size along the spine reflects how much neural tissue sits in each region. In quadrupeds, the cervical region contains the cervical enlargement, which supplies nerves to the forelimbs, so the spinal cord is thickest there. To accommodate this thicker cord (and the brainstem just above it), the vertebral canal in the cervical region is the widest. The thoracic region is tighter because of the rib attachments, and the sacral region is relatively narrow due to the fused sacral bones. Although there is a lumbar enlargement for the hindlimbs, its canal isn’t as large as the cervical one. So the cervical region has the largest vertebral canal.