The Third Cervical Vertebra (C3)

The C3 vertebra is part of the lower cervical spine and acts as a support link between the upper cervical spine and the rest of the vertebral column. It shares structural features with C4 and C5, forming a stable yet mobile segment. It helps in neck flexion, extension, lateral bending, and rotation. The spinal nerve exiting here (C3) is vital for neck muscle control and contributes to the phrenic nerve, which controls the diaphragm.

Key Features:

• Vertebra type: Typical cervical vertebra (like C4–C6). Small body, large vertebral foramen, bifid spinous process.
• Transverse foramen: Passage for vertebral artery.
• Facet joints: Allow movement and protect spinal cord.
• Nerve involved: C3 spinal nerve.
• Muscle control: Helps supply neck muscles, trapezius, and part of the diaphragm (via phrenic nerve).
• Clinical link: Lesions here affect breathing, neck stiffness, and sometimes referred pain in shoulder.
  

Questions & Answers

1. What kind of vertebra is C3?
   Ans: A typical cervical vertebra with common features like bifid spinous process and transverse foramen.

2. What nerve exits at C3?
   Ans: The C3 spinal nerve.

3. Which important nerve does C3 contribute to?
   Ans: The phrenic nerve, which innervates the diaphragm.

4. What clinical symptoms can a C3 lesion cause?
   Ans: Neck pain, breathing difficulty, shoulder pain, and muscle weakness in the neck.

5. Why is C3 clinically important in osteopathy?
   Ans: It affects head/neck movement and breathing via phrenic nerve contribution.

6. What artery passes through the transverse foramen of C3?
   Ans: The vertebral artery, which supplies blood to the brainstem.

Clinical Insight

• A lesion at C3 can disturb phrenic nerve signaling, causing difficulty in breathing or shallow respiration.
• Tightness in trapezius or scalene muscles may signal C3 nerve dysfunction.
• Gentle mobilization can improve nerve flow and reduce referred pain to the shoulder or jaw.