The cervical spinal nerve 8 (C8) is a
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 body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the ...
of the
cervical segment.
American Medical Association
Nervous System -- Groups of Nerves
It originates from the spinal column from below the cervical vertebra 7
In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...
(C7).
Innervation
The C8 nerve forms part of the radial
Radial is a geometric term of location which may refer to:
Mathematics and Direction
* Vector (geometric), a line
* Radius, adjective form of
* Radial distance, a directional coordinate in a polar coordinate system
* Radial set
* A bearing f ...
and ulnar nerve
In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is ...
s via the brachial plexus
The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in t ...
, and therefore has motor and sensory function in the upper limb
The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shou ...
.
Sensory
The C8 nerve receives sensory afferents from the C8 dermatome. This consists of all the skin on the little finger
The little finger, or pinkie, also known as the baby finger, fifth digit, or pinky finger, is the most ulnar and smallest digit of the human hand, and next to the ring finger.
Etymology
The word "pinkie" is derived from the Dutch word ''p ...
, and continuing up slightly past the wrist on the palmar and dorsal aspects of the hand and forearm.[Drake et al. Gray's Anatomy for Students. Second Edition (2010).] Clinically a test of the pad of the little finger is often used to assess C8 integrity.[Aland et al. University of Queensland School of Medicine Clinical Skills Handbook 2010]
Motor
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.
Trunk
* ''Pectoralis major
The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, ...
- Medial and lateral pectoral nerves ( C5, C6, C7, C8, T1)''
* Pectoralis minor - Medial pectoral nerve ( C5, C6, C7, C8, T1)
* ''Latissimus dorsi
The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsorum'') comes from ...
- Thoracodorsal nerve ( C6, C7, C8)''
Upper arm
* ''Triceps brachii
The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of 3 parts: the medial, lateral, and long head. It is the muscle principally respon ...
- Radial nerve ( C6, C7, C8)''
Forearm
* Flexor carpi ulnaris
The flexor carpi ulnaris (FCU) is a muscle of the forearm that flexes and adducts at the wrist joint.
Structure Origin
The flexor carpi ulnaris has two heads; a humeral head and ulnar head. The humeral head originates from the medial epicondyle of ...
- Ulnar nerve ( C7, C8, T1)
* Palmaris longus
The palmaris longus is a muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much long ...
- Median nerve ( C7, C8)
* Flexor digitorum superficialis
Flexor digitorum superficialis (''flexor digitorum sublimis'') is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints.
It is in the anterior compartment of the forearm. It is sometimes considered to be the deepest p ...
- Median nerve (C8, T1)
* Flexor digitorum profundus
The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.
Togeth ...
- Median and Ulnar nerves (C8, T1)
* Flexor pollicis longus
The flexor pollicis longus (; FPL, Latin ''flexor'', bender; ''pollicis'', of the thumb; ''longus'', long) is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus. This muscle is un ...
- Median nerve ( C7, C8)
* Pronator quadratus
Pronator quadratus is a square-shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand.
Structure
Its fibres run perpendicular to the direction of the arm, running from the most distal quarter of the a ...
- Median nerve ( C7, C8)
* ''Extensor carpi radialis brevis
In human anatomy, extensor carpi radialis brevis is a muscle in the forearm that acts to extend and abduct the wrist. It is shorter and thicker than its namesake extensor carpi radialis longus which can be found above the proximal end of the exten ...
- Deep branch of the radial nerve ( C7, C8)''
* ''Extensor digitorum
The extensor digitorum muscle (also known as extensor digitorum communis) is a muscle of the posterior forearm present in humans and other animals. It extends the medial four digits of the hand. Extensor digitorum is innervated by the posterior int ...
- Posterior interosseous nerve ( C7, C8)''
* '' Extensor digiti minimi - Posterior interosseous nerve ( C7, C8)''
* ''Extensor carpi ulnaris
In human anatomy, the extensor carpi ulnaris is a skeletal muscle located on the ulnar side of the forearm. The extensor carpi ulnaris acts to extend and adduct at the carpus/wrist from anatomical position.
Being an extensor muscle, extensor carp ...
- Posterior interosseous nerve ( C7, C8)''
* '' Anconeus - Radial nerve ( C6, C7, C8)''
* ''Abductor pollicis longus
In human anatomy, the abductor pollicis longus (APL) is one of the extrinsic muscles of the hand. Its major function is to abduct the thumb at the wrist. Its tendon forms the anterior border of the anatomical snuffbox.
Structure
The abductor ...
- Posterior interosseous nerve ( C7, C8)''
* ''Extensor pollicis brevis
In human anatomy, the extensor pollicis brevis is a skeletal muscle on the dorsal side of the forearm. It lies on the medial side of, and is closely connected with, the abductor pollicis longus. The extensor pollicis brevis (EPB) belongs to the ...
- Posterior interosseous nerve ( C7, C8)''
* ''Extensor pollicis longus
In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together ...
- Posterior interosseous nerve ( C7, C8)''
* ''Extensor indicis
In human anatomy, the extensor indicis roprius'' is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus. Its tendon goes to the index finger, which it exte ...
- Posterior interosseous nerve ( C7, C8)''
Hand
* ''Palmaris brevis
Palmaris brevis muscle is a thin, quadrilateral muscle, placed beneath the integument of the ulnar side of the hand. It acts to fold the skin of the hypothenar eminence transversally.
Structure
Origin and insertion
Palmaris brevis muscle is lo ...
- Superficial branch of ulnar nerve (C8, T1)''
* '' Dorsal interossei - Deep branch of ulnar nerve (C8, T1)''
* ''Palmar interossei
In human anatomy, the palmar or volar interossei (interossei volares in older literature) are three small, unipennate muscles in the hand that lie between the metacarpal bones and are attached to the index, ring, and little fingers. They are sm ...
- 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
The opponens pollicis is a small, triangular muscle in the hand, which functions to oppose the thumb. It is one of the three thenar muscles. It lies deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis.
Structure
The op ...
- Recurrent branch of median nerve (C8, T1)''
* ''Abductor pollicis brevis
The abductor pollicis brevis is a muscle in the hand that functions as an abductor of the thumb.
Structure
The abductor pollicis brevis is a flat, thin muscle located just under the skin. It is a thenar muscle, and therefore contributes to the ...
- Recurrent branch of median nerve (C8, T1)''
* ''Flexor pollicis brevis
The flexor pollicis brevis is a muscle in the hand that flexes the thumb. It is one of three thenar muscles. It has both a superficial part and a deep part.
Origin and insertion
The muscle's superficial head arises from the distal edge of the fl ...
- Recurrent branch of median nerve (C8, T1)''
* ''Opponens digiti minimi
The opponens digiti minimi (opponens digiti quinti in older texts) is a muscle in the hand. It is of a triangular form, and placed immediately beneath the palmaris brevis, abductor digiti minimi and flexor digiti minimi brevis. It is one of t ...
- 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
File:Slide5y.JPG, Cervical spinal nerve 8
References
{{DEFAULTSORT:Cervical Spinal Nerve 8
Spinal nerves