Brachial plexus

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Brachial plexus

The brachial plexus
Plexus

A plexus is a network. It has more specific meanings in multiple fields....
is an arrangement of nerve fibers, running from the spine, formed by the ventral rami of the lower cervical and upper thoracic nerve roots, specifically from above the fifth cervical vertebra to underneath the first thoracic vertebra (C5

Cervical spinal nerve 5

The cervical spinal nerve 5 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 5 ....
-T1

Thoracic spinal nerve 1

The thoracic spinal nerve 1 is a spinal nerve of the thoracic segment..It originates from the spinal column from below the thoracic vertebra 1 ....
). It proceeds through the neck, the axilla (armpit region) and into the arm.

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Function

The brachial plexus is responsible for cutaneous and muscular innervation of the entire upper limb, with two exceptions: the trapezius muscle innervated by the spinal accessory nerve and an area of skin near the axilla innervated by the intercostobrachialis nerve.

Therefore, brachial plexus lesion

Brachial plexus lesion

Brachial plexus lesions are classified as either traumatic or obstetric....
s can lead to severe functional impairment.

Anatomy

Path

One can remember the order of brachial plexus elements by way of the mnemonic, "Read The Damn Cadaver Book" (Or, alternatively, Real Teenagers Drink Cold Beer") - Roots, Trunks, Divisions, Cords, Branches or - Roots, Trunks, Divisions, Cords, Collateral/Pre-terminal Branches, and (Terminal) Branches.

The five roots are the five anterior rami of the spinal nerve
Spinal nerve

The term spinal nerve generally refers to the mixed spinal nerve, which is formed from the dorsal and ventral roots that come out of the spinal cord....
s, after they have given off their segmental supply to the muscles of the neck
Neck

The neck is the part of the body on many limbed vertebrates that distinguishes the head from the torso or trunk. The scientific term signifying "of the neck" is nuchal....
.

These roots merge to form three trunks:

"superior" or "upper" (C5
Cervical spinal nerve 5

The cervical spinal nerve 5 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 5 ....
-C6
Cervical spinal nerve 6

The cervical spinal nerve 6 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 6 ....
)
"middle" (C7
Cervical spinal nerve 7

The cervical spinal nerve 7 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 7 ....
)
"inferior" or "lower" (C8
Cervical spinal nerve 8

The cervical spinal nerve 8 is a spinal nerve of the cervical segment.It originates from the spinal column from below the cervical vertebra 7 ....
-T1
Thoracic spinal nerve 1

The thoracic spinal nerve 1 is a spinal nerve of the thoracic segment..It originates from the spinal column from below the thoracic vertebra 1 ....
)

Each trunk then splits in two, to form six divisions:

anterior division of the upper, middle and lower trunks
posterior division of the upper, middle, and lower trunks

These six divisions will regroup to become the three cords. The cords are named by their position in respect to the axillary artery
Axillary artery

In human anatomy, the axillary artery is a large blood vessel that conveys oxygenated blood to the lateral aspect of the thorax, the axilla and the upper limb....
.

The posterior cord
Posterior cord

The posterior cord is a part of the brachial plexus. It consists of contributions from all of the roots of the brachial plexus.The posterior cord gives rise to the following nerves:...
is formed from the three posterior divisions of the trunks (C5-T1)
The lateral cord
Lateral cord

The Lateral cord is a division of the brachial plexus.The lateral cord gives rise to the following nerves:*The lateral pectoral nerve, C5, C6 and C7 to the pectoralis major muscle...
is the anterior divisions from the upper and middle trunks (C5-C7)
The medial cord
Medial cord

The Medial cord is a division of the brachial plexus.The medial cord gives rise to the following nerves:*The median pectoral nerve, C8 and T1, to the pectoralis muscle...
is simply a continuation of the anterior division of the lower trunk (C8-T1)

The branches are listed below. Most branch from the cords, but a few branch (indicated in italics) directly from earlier structures. The five in bold are considered "terminal branches".

Diagram

Specific branches

One can remember the specific branches of lateral, posterior and medial cord using the mnemonic LML ULNAR M4U respectively.

LML - lateral pectoral nerve
Lateral pectoral nerve

The lateral pectoral nerve arises from the lateral cord of the brachial plexus, and through it from the fifth, sixth, and seventh cervical nerves....
, musculocutaneous nerve
Musculocutaneous nerve

The musculocutaneous nerve arises from the lateral cord of the brachial plexus, opposite the lower border of the Pectoralis minor, its fibers being derived from the fifth, sixth, and seventh cervical nerves....
, lateral root of the median nerve
Median nerve

The median nerve is a nerve that runs down the arm and forearm. It is one of the five main nerves originating from the brachial plexus.The median nerve is formed from parts of the medial and lateral cords of the brachial plexus, and continues down the arm to enter the forearm with the brachial artery....
.
ULNAR - upper subscapular nerve
Upper subscapular nerve

The upper subscapular enters the upper part of the Subscapularis, and is frequently represented by two branches. It is derived from C5, C6 nerve fibers, and branches from the posterior cord of the brachial plexus....
, lower subscapular nerve
Lower subscapular nerve

The lower subscapular is a nerve which supplies the lower part of the Subscapularis, and ends in the Teres major; the latter muscle is sometimes supplied by a separate branch....
, nerve to latissmus dorsi (thoracodorsal nerve
Thoracodorsal nerve

The thoracodorsal nerve , a branch of the posterior cord of the brachial plexus, derives its fibers from the sixth, seventh, and eighth cervical nerves; it follows the course of the subscapular artery, along the posterior wall of the axilla to the Latissimus dorsi, in which it may be traced as far as the lower border of the muscle....
) , axillary nerve
Axillary nerve

The axillary nerve is a nerve of the human body, that comes off the posterior cord of the brachial plexus at the level of the axilla and carries nerve fibers from C5 and C6....
, radial nerve
Radial nerve

The radial nerve is a nerve in the human body that supplies the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm....
.
M4U - medial pectoral nerve
Medial pectoral nerve

The medial pectoral nerve arises from the medial cord of the plexus and through it from the Cervical vertebrae and Thoracic vertebrae.It passes behind the first part of the axillary artery, curves forward between the axillary artery and vein, and unites in front of the artery with a filament from the Lateral pectoral nerve....
, medial root of the median nerve
Median nerve

The median nerve is a nerve that runs down the arm and forearm. It is one of the five main nerves originating from the brachial plexus.The median nerve is formed from parts of the medial and lateral cords of the brachial plexus, and continues down the arm to enter the forearm with the brachial artery....
, medial cutaneous nerve of the arm , medial cutaneous nerve of the forearm , ulnar nerve
Ulnar nerve

In human anatomy, the ulnar nerve is a nerve which runs near the ulna bone. The ulnar nerve is the largest unprotected nerve in the human body , and the only unprotected nerve that does not serve a purely sensory function ....
.

From	Nerve	Roots	Muscles	Cutaneous Cutaneous innervation Cutaneous innervation refers to the area of the skin which is supplied by a specific nerve, that is, by a cutaneous nerve.Dermatome s are similar; however, a dermatome only specifies the area served by a spinal nerve....
roots	dorsal scapular nerve Dorsal scapular nerve The dorsal scapular nerve arises from the brachial plexus, usually from the plexus root of C5.It provides motor innervation to the rhomboid muscles, which pull the scapula towards the spine and levator scapulae muscle, which elevates the scapula....	C5 Cervical spinal nerve 5 The cervical spinal nerve 5 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 5 ....	rhomboid muscle Rhomboid muscle The rhomboid muscles, often simply called the rhomboids, are rhombus-shaped muscles associated with the scapula and are chiefly responsible for its retraction.... s and levator scapulae	-
roots	long thoracic nerve Long thoracic nerve The long thoracic nerve supplies the Serratus anterior. This nerve characteristically arises by three roots from the fifth, sixth, and seventh cervical nerves but the root from C7 may be absent....	C5, C6 Cervical spinal nerve 6 The cervical spinal nerve 6 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 6 .... , C7 Cervical spinal nerve 7 The cervical spinal nerve 7 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 7 ....	serratus anterior	-
superior trunk	nerve to the subclavius Nerve to the subclavius The nerve to the Subclavius is a small filament, which arises from the point of junction of the fifth and sixth cervical nerves.It descends to the subclavius muscle in front of the third part of the subclavian artery and the lower trunk of the plexus, and is usually connected by a filament with the phrenic nerve....	C5, C6	subclavius muscle Subclavius muscle The Subclavius is a small triangular muscle, placed between the clavicle and the first rib. Along with the pectoralis major and pectoralis minor muscles, the subclavius muscle makes up the anterior wall of the axilla....	-
superior trunk	suprascapular nerve Suprascapular nerve The suprascapular nerve arises from the trunk formed by the union of the fifth and sixth cervical nerves. It innervates the supraspinatus muscles and infraspinatus muscles....	C5, C6	supraspinatus and infraspinatus	-
lateral cord	lateral pectoral nerve Lateral pectoral nerve The lateral pectoral nerve arises from the lateral cord of the brachial plexus, and through it from the fifth, sixth, and seventh cervical nerves....	C5, C6, C7	pectoralis major (by communicating with the medial pectoral nerve Medial pectoral nerve The medial pectoral nerve arises from the medial cord of the plexus and through it from the Cervical vertebrae and Thoracic vertebrae.It passes behind the first part of the axillary artery, curves forward between the axillary artery and vein, and unites in front of the artery with a filament from the Lateral pectoral nerve.... )	-
lateral cord	musculocutaneous nerve Musculocutaneous nerve The musculocutaneous nerve arises from the lateral cord of the brachial plexus, opposite the lower border of the Pectoralis minor, its fibers being derived from the fifth, sixth, and seventh cervical nerves....	C5, C6, C7	coracobrachialis, brachialis and biceps brachii	becomes the lateral cutaneous nerve of the forearm
lateral cord	lateral root of the median nerve Median nerve The median nerve is a nerve that runs down the arm and forearm. It is one of the five main nerves originating from the brachial plexus.The median nerve is formed from parts of the medial and lateral cords of the brachial plexus, and continues down the arm to enter the forearm with the brachial artery....	C5, C6, C7	fibres to the median nerve	-
posterior cord	upper subscapular nerve Upper subscapular nerve The upper subscapular enters the upper part of the Subscapularis, and is frequently represented by two branches. It is derived from C5, C6 nerve fibers, and branches from the posterior cord of the brachial plexus....	C5, C6	subscapularis (upper part)	-
posterior cord	thoracodorsal nerve Thoracodorsal nerve The thoracodorsal nerve , a branch of the posterior cord of the brachial plexus, derives its fibers from the sixth, seventh, and eighth cervical nerves; it follows the course of the subscapular artery, along the posterior wall of the axilla to the Latissimus dorsi, in which it may be traced as far as the lower border of the muscle.... (middle subscapular nerve)	C6, C7, C8	latissimus dorsi	-
posterior cord	lower subscapular nerve Lower subscapular nerve The lower subscapular is a nerve which supplies the lower part of the Subscapularis, and ends in the Teres major; the latter muscle is sometimes supplied by a separate branch....	C5, C6	subscapularis (lower part ) and teres major	-
posterior cord	axillary nerve Axillary nerve The axillary nerve is a nerve of the human body, that comes off the posterior cord of the brachial plexus at the level of the axilla and carries nerve fibers from C5 and C6....	C5, C6	anterior branch: deltoid Deltoid Deltoid can refer to:* The deltoid muscle, a muscle in the shoulder* Kite , also known as a deltoid, a type of quadrilateral* A deltoid curve, a three-sided hypocycloid... and a small area of overlying skin posterior branch: teres minor and deltoid muscles	posterior branch becomes upper lateral cutaneous nerve of the arm
posterior cord	radial nerve Radial nerve The radial nerve is a nerve in the human body that supplies the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm....	C5, C6, C7, C8, T1	triceps brachii, supinator, anconeus, the extensor muscle Extensor muscle An extensor muscle is any muscle that opens a joint increasing the angle between components of a limb, such as straightening the knee or Elbow-joint and bending the wrist or vertebral column.... s of the forearm Forearm The forearm is the structure on the upper limb, between the Elbow-joint and the wrist.. This term is used in anatomy to distinguish it from the arm .... , and brachioradialis Brachioradialis Brachioradialis is a muscle of the forearm that acts to flex the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm....	skin of the posterior arm as the posterior cutaneous nerve of the arm
medial cord	medial pectoral nerve Medial pectoral nerve The medial pectoral nerve arises from the medial cord of the plexus and through it from the Cervical vertebrae and Thoracic vertebrae.It passes behind the first part of the axillary artery, curves forward between the axillary artery and vein, and unites in front of the artery with a filament from the Lateral pectoral nerve....	C8, T1	pectoralis major and pectoralis minor	-
medial cord	medial root of the median nerve Median nerve The median nerve is a nerve that runs down the arm and forearm. It is one of the five main nerves originating from the brachial plexus.The median nerve is formed from parts of the medial and lateral cords of the brachial plexus, and continues down the arm to enter the forearm with the brachial artery....	C8, T1	fibres to the median nerve	portions of hand not served by ulnar or radial
medial cord	medial cutaneous nerve of the arm	C8, T1	-	front and medial skin of the arm Arm In anatomy, an arm is one of the upper limbs of an animal. The term arm can also be used for analogous structures, such as one of the paired upper limbs of a four-legged animal, or the cephalopod arm....
medial cord	medial cutaneous nerve of the forearm	C8, T1	-	medial skin of the forearm
medial cord	ulnar nerve Ulnar nerve In human anatomy, the ulnar nerve is a nerve which runs near the ulna bone. The ulnar nerve is the largest unprotected nerve in the human body , and the only unprotected nerve that does not serve a purely sensory function ....	C8, T1	flexor carpi ulnaris, the medial 2 bellies of flexor digitorum profundus, most of the small muscles of the hand Hand The hands are the two intricate, prehensile, multi-fingered body parts normally located at the end of each arm of a human or other primate. They are the chief organs for physically manipulating the environment, using anywhere from the roughest motor skills to the finest , and since the fingertips contain some of the densest areas of nerve e...	the skin of the medial side of the hand and medial one and a half fingers on the palmar side and medial two and a half fingers on the dorsal side

Additional images

External links

at Newcastle University

Brachial plexus

Function

Anatomy

Path

Diagram

Specific branches

Additional images

See also

External links