Spinal nerve C5
Nervus spinalis C5
- Related terms: Fifth cervical nerve; C5
Definition
The fifth cervical spinal nerve C5 is a mixed nerve, carrying both somatic efferent (motor) and somatic afferent (sensory) fibers. It arises from the C5 spinal segment of the spinal cord.
a) Roots
The spinal nerve C5 is formed by the union of two roots:
1. Posterior (dorsal) root:
Contains sensory fibers that transmit signals from peripheral structures to the spinal cord.
These fibers enter the dorsal gray horn within the spinal cord.
2. Anterior (ventral) root:
Composed of motor fibers that originate from the anterior gray horn of the spinal cord.
These fibers transmit motor commands to peripheral muscles through the spinal nerve and its branches.
b) Mixed spinal nerve and rami
At the intervertebral foramen, the anterior and posterior roots merge to form the mixed C5 spinal nerve, containing both motor and sensory fibers. The nerve exits the vertebral column between the C4 and C5 vertebrae and divides into two rami:
1. Anterior (ventral) ramus:
Provides motor and sensory innervation to the upper limb.
Communicates with the sympathetic trunk via a gray ramus communicans, which carries postganglionic sympathetic fibers.
2. Posterior (dorsal) ramus:
Provides motor innervation to the deep muscles of the upper back.
Provides sensory innervation to the skin overlying the upper back.
A. ANTERIOR RAMUS OF SPINAL NERVE C5:
The anterior ramus of the spinal nerve C5 exits the vertebral canal through the intervertebral foramen located between the C4 and C5 vertebrae. This mixed nerve contains both motor (somatic efferent) and sensory (somatic afferent) fibers. In the neck, it merges with the anterior ramus of the spinal nerve C6 to form the superior trunk of the brachial plexus.
Key functions and innervations
Motor Innervation (Somatic Efferent Fibers): | Sensory Innervation (Somatic Afferent Fibers): | ||
The anterior ramus of spinal nerve C5, which continues as the superior trunk of the brachial plexus, supplies motor innervation to several upper limb muscles, including: 1. Muscles of the shoulder: Deltoid (C5, C6), innervated via the axillary nerve. Levator scapulae (C3, C4, C5) innervated via the dorsal scapular nerve. Rhomboid minor and major (C4, C5), innervated via the dorsal scapular nerve. 2. Muscles of the posterior scapular region: Supraspinatus (C5, C6), Infraspinatus (C5, C6); both innervated via the suprascapular nerve. Teres minor (C5, C6) innervated via the axillary nerve. 3. Muscles of the posterior wall of the axilla: Subscapularis (C5-C7), innervated via upper and lower subscapular nerves. Teres major (C5-C7), innervated via lower subscapular nerve. 4. Muscles of the medial wall of the axilla: Serratus anterior (C5-C7) innervated via the long thoracic nerve. 5. Muscles of the anterior wall of the axilla: Clavicular head (C5, C6) of the pectoralis major muscle, innervated via the lateral pectoral nerves. Subclavius (C5, C6) innervated via the nerve to subclavius. 6. Muscles of the anterior arm: Coracobrachialis muscle (C5-C7), biceps brachii (C5, C6), and brachialis (C5, C6), all innervated via the musculocutaneous nerve. 7. Forearm muscles (extensor side): Brachioradialis (C5, C6), innervated via the radial nerve. Additional structures innervated by the spinal nerve C5 include the: Diaphragm, innervated via the phrenic nerve (C3, C4, C5). Scalene muscles (of the neck), i.e. anterior scalene (C4-C7), middle scalene (C3-C7), and posterior scalene muscles (C5-C7). Pre-vertebral muscles, such as the longus colii (specifically, its inferior portion). | The sensory fibers of the anterior ramus of spinal nerve C5 innervate the skin corresponding to the C5 dermatome, which encompasses the upper lateral arm region. | ||
B. POSTERIOR RAMUS OF SPINAL NERVE C5:
The posterior ramus of the spinal nerve C5 divides into medial and lateral branches, each with distinct patterns of innervation:
Lateral branch: | Medial branch: | ||
The lateral branch of the posterior ramus courses laterally to supply: Muscles of the erector spinae group: including the iliocostalis cervicis and longissimus cervicis. Cutaneous innervation: Toward its termination, this branch transitions to cutaneous innervation, supplying sensory fibers to the skin over the posterior cervical region. | The medial branch of the posterior ramus of the C5 nerve primarily innervates: Deep paraspinal muscles, including the multifidus, semispinalis cervicis and interspinales muscles. Facet joints: Supplies sensory fibers to the facet joints of the cervical spine. However, it does not provide any cutaneous sensory innervation to the skin. |
C. ADDITIONAL STRUCTURES ASSOCIATED WITH SPINAL NERVE C5:
a) Recurrent Meningeal Nerve (Meningeal branch):
The recurrent meningeal nerve (or meningeal branch) originates from either the C5 spinal nerve or one of its rami. This small nerve re-enters the vertebral canal through the intervertebral foramen and provides sensory innervation to:
The meninges (protective coverings of the spinal cord),
The annulus fibrosus of the intervertebral discs,
The vertebral bodies and periosteum,
Adjacent blood vessels.
b) Sympathetic connections:
The spinal nerve C5 connects to the sympathetic trunk through the gray ramus communicant. The gray ramus communicant enables the postganglionic sympathetic fibers to reach peripheral targets such as sweat glands and blood vessels.
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SUMMARY TABLE
STRUCTURES INNERVATED BY THE SPINAL NERVE C5 | |||
ANTERIOR RAMUS | POSTERIOR RAMUS | ||
MOTOR STRUCTURES | SENSORY STRUCTURES | MOTOR STRUCTURES | SENSORY STRUCTURES |
Deltoid (C5, C6), Levator scapulae (C3, C4, C5), Rhomboid minor and major (C4, C5), Supraspinatus (C5, C6), Infraspinatus (C5, C6), Teres minor (C5, C6), Subscapularis (C5-C7), Teres major (C5-C7), Serratus anterior (C5-C7), Clavicular head (C5, C6) of the pectoralis major muscle, Subclavius (C5, C6), Coracobrachialis muscle (C5-C7), biceps brachii (C5, C6), and brachialis (C5, C6), Brachioradialis (C5, C6). Diaphragm, anterior scalene (C4-C7), middle scalene (C3-C7), and posterior scalene muscles (C5-C7), longus colii (its inferior part). | C5 dermatome of skin encompassing the upper lateral arm. | Skin over the posterior cervical region; lower neck. | |
References
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