Spinal Canal and Spinal Cord Relationships

Question 1

At the intervertebral foramen, what is the relationship between spinal nerve number and vertebral number?

Answer 1

• In the cervical spine, spinal nerves exit above the segment they are numbered after (C8 nerve is the exception to this rule).
• In the thoracic spine, lumbar spine, and sacrum, spinal nerves exit below the segment they are numbered after (Co1 nerve is the exception to this rule).
• C3 nerve exits above C3 or between C2/C3
• T6 nerve exits below T6 or between T6/T7

Question 2

What is the relationship between rib number and vertebral numbers at the costocentral joint?

Answer 2

• Rib number always equates to same vertebral number at the costocentral joint
• Rib 3 articulates with T3 segment and also with the T2 segment
• Only ribs 1, 11, and 12 typically joint with a single segment

Question 3

What is the relationship between spinal nerve number, rib number, and vertebral number in a thoracic intervertebral foramen?

Answer 3

• The spinal nerve number relates to the upper segment number in the vertebral couple.
• The rib number relates to the lower segment number in the vertebral couple.
• i.e., T3 nerve exits the intervertebral foramen formed by T3/T4 and rib 4 joints with this vertebral couple.