The Fifth Cervical Vertebra (C5)

 The C5 vertebra is structurally similar to C3 and C4 — a typical cervical vertebra — but it holds increased clinical significance due to the C5 spinal nerve, which is a major motor root for shoulder muscles (especially deltoid and rotator cuff). It plays a key role in neck motion, especially flexion and lateral bending, and lies near the thyroid gland anteriorly.

Key Points

1. Type: Typical cervical vertebra (like C3–C6)
2. Spinal nerve C5: Major motor supply to deltoid, biceps, supraspinatus
3. Motion: Assists in neck flexion and side-bending.
4. Landmark level: Just below the thyroid cartilage
5. Vertebral artery: Still passes through transverse foramen
6. Facet joints: Guide movement and prevent over rotation.

Important Questions & Answers

1. Q: What type of vertebra is C5?

    A: A typical cervical vertebra.
2. Q: Which nerve exits at C5?
    A: The C5 spinal nerve, which forms part of the brachial plexus.
3. Q: What muscles does the C5 nerve root innervate?
     A: Deltoid, biceps, supraspinatus, and partially the diaphragm (via phrenic nerve).
4. Q: What clinical signs may appear in C5 dysfunction?
    A: Weak shoulder abduction, decreased biceps reflex, pain/numbness in lateral arm.
5. Q: Is there any organ close to C5?
    A: Yes, thyroid gland and recurrent laryngeal nerve lie anteriorly.
6. Q: What movements are supported at C5?
    A: Flexion, extension, and lateral bending of the neck.

Clinical Insight

1. C5 dysfunction may lead to:

Shoulder pain (even when shoulder is normal)
Deltoid weakness or atrophy
Referred pain to lateral neck and upper arm

2. Commonly affected by:

Forward head posture
Chronic neck tension (especially in desk workers)
May also be hypertonic from sympathetic activity (linked to thyroid tension anteriorly)