The cervical spinal nerve 8 (C8) is a spinal nerve of the cervical segment.[1]
It originates from the spinal column from below the cervical vertebra 7 (C7).
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Innervation [link]
The C8 nerve forms part of the radial and ulnar nerves via the brachial plexus, and therefore has motor and sensory function in the upper limb.
Sensory [link]
The C8 nerve receives sensory afferents from the C8 dermatome. This consists of all the skin on the little finger, and continuing up slightly past the wrist on the palmar and dorsal aspects of the hand and forearm [2]. Clinically a test of the pad of the little finger is often used to assess C8 integrity [3].
Motor [link]
The C8 nerve contributes to the motor innervation of many of the muscles in the trunk and upper limb. Its primary function is the flexion of the fingers, and this is used as the clinical test for C8 integrity, in conjunction with the finger jerk reflex [3].
The particular muscles receive innervation from C8 [2] (shown by specific nerve and spinal nerve segments; muscles in italics only have a minor contribution from C8) :
Trunk [link]
- Pectoralis major - Medial and lateral pectoral nerves (C5, C6, C7,C8, T1)
- Pectoralis minor - Medial pectoral nerve (C5, C6, C7,C8, T1)
- Latissimus dorsi - Thoracodorsal nerve (C6, C7,C8)
Upper arm [link]
- Triceps brachii - Radial nerve (C6, C7,C8)
Forearm [link]
- Flexor carpi ulnaris - Ulnar nerve (C7, C8, T1)
- Palmaris longus - Median nerve (C7,C8)
- Flexor digitorum superficialis - Median nerve (C8, T1)
- Flexor digitorum profundus - Median and Ulnar nerves (C8, T1)
- Flexor pollicis longus - Median nerve (C7,C8)
- Pronator quadratus - Median nerve (C7,C8)
- Extensor carpi radialis brevis - Deep branch of the radial nerve (C7,C8)
- Extensor digitorum - Posterior interosseous nerve (C7,C8)
- Extensor digiti minimi - Posterior interosseous nerve (C7,C8)
- Extensor carpi ulnaris - Posterior interosseous nerve (C7,C8)
- Anconeus - Radial nerve (C6, C7,C8)
- Abductor pollicis longus - Posterior interosseous nerve (C7,C8)
- Extensor pollicis brevis - Posterior interosseous nerve (C7,C8)
- Extensor pollicis longus - Posterior interosseous nerve (C7,C8)
- Extensor indicis - Posterior interosseous nerve (C7,C8)
Hand [link]
- Palmaris brevis - Superficial branch of ulnar nerve (C8, T1)
- Dorsal interossei - Deep branch of ulnar nerve (C8, T1)
- Palmar interossei - Deep branch of ulnar nerve (C8, T1)
- Adductor pollicis - Deep branch of ulnar nerve (C8, T1)
- Lumbricals - Deep branch of ulnar nerve, Digital branches of median nerve
- Opponens pollicis - Recurrent branch of median nerve (C8, T1)
- Abductor pollicis brevis - Recurrent branch of median nerve (C8, T1)
- Flexor pollicis brevis - Recurrent branch of median nerve (C8, T1)
- Opponens digiti minimi - Deep branch of ulnar nerve (C8, T1)
- Abductor digiti minimi - Deep branch of ulnar nerve (C8, T1)
- Flexor digiti minimi brevis - Deep branch of ulnar nerve (C8, T1)
Additional Images [link]
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Cervical spinal nerve 8
References [link]
- ^ American Medical Association Nervous System -- Groups of Nerves
- ^ a b Drake et al. Gray's Anatomy for Students. Second Edition (2010).
- ^ a b Aland et al. University of Queensland School of Medicine Clinical Skills Handbook 2010
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Spinal nerve
A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the corresponding cervical, thoracic, lumbar, sacral and coccygeal regions of the spine. There are eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves. The spinal nerves are part of the peripheral nervous system.
Structure
Each spinal nerve is formed from the combination of nerve fibers from its posterior and anterior roots. The posterior root is the afferent sensory root and carries sensory information to the brain. The anterior root is the efferent motor root and carries motor information from the brain. The spinal nerve emerges from the spinal column through an opening (intervertebral foramen) between adjacent vertebrae. This is true for all spinal nerves except for the first spinal nerve pair (C1), which emerges between the occipital bone and the atlas (the first vertebra). Thus the cervical nerves are numbered by the vertebra below, except spinal nerve C8, which exists below vertebra C7 and above vertebra T1. The thoracic, lumbar, and sacral nerves are then numbered by the vertebra above. In the case of a lumbarized S1 vertebra (aka L6) or a sacralized L5 vertebra, the nerves are typically still counted to L5 and the next nerve is S1.
Cervical spinal nerve 4
The cervical spinal nerve 4 (C4) is a spinal nerve of the cervical segment.
It originates from the spinal column from above the cervical vertebra 4 (C4).
Its control of the thoracic diaphragm has inspired a medical mnemonic: "Cut C4, breathe no more."
Additional Images
Cervical spinal nerve 4
Cervical spinal nerve 4
References
Cervical spinal nerve 2
The cervical spinal nerve 2 (C2) is a spinal nerve of the cervical segment.
It originates from the spinal column from above the cervical vertebra 2 (C2).
