Brachial plexus

Nerve: Brachial plexus
The right brachial plexus with its short branches, viewed from in front.
Latin	plexus brachialis
Gray's	subject #210 930
Innervates	Sensory and motor innervation to the upper limb
From	C5, C6, C7, C8, T1
MeSH	Brachial+plexus

The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots (C5-C8, T1). It proceeds through the neck, the axilla (armpit region), and into the arm. It is a bunch of nerves passing through the cervico-axillary canal to reach axilla and supplies brachium, antebrachium and hand.

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 (CN XI) and an area of skin near the axilla innervated by the intercostobrachial nerve.

Lesions can lead to severe functional impairment.

Anatomy

Path

The brachial plexus is divided into Roots, Trunks, Divisions, Cords, and Branches. There are five "terminal" branches and numerous other "pre-terminal" or "collateral" branches that leave the plexus at various points along its length.

• The five roots are the five anterior rami of the spinal nerves, after they have given off their segmental supply to the muscles of the neck.

• These roots merge to form three trunks:
  • "superior" or "upper" (C5-C6)
  • "middle" (C7)
  • "inferior" or "lower" (C8, T1)

• Each trunk then splits in two, to form six divisions:
  • anterior divisions of the upper, middle, and lower trunks
  • posterior divisions of the upper, middle, and lower trunks

• These six divisions will regroup to become the three cords. The cords are named by their position with respect to the axillary artery.
  • The posterior cord is formed from the three posterior divisions of the trunks (C5-C8,T1)
  • The lateral cord is the anterior divisions from the upper and middle trunks (C5-C7)
  • The medial cord 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 on the left are considered "terminal branches".

Diagram

Anatomical illustration of the brachial plexus with areas of roots, trunks, divisions and cords marked. Clicking on names of branches will link to their Wikipedia entry.

Diagrammatic representation of the brachial plexus using colour to illustrate the contributions of each nerve root to the branches

Specific branches

Bold indicates primary spinal root component of nerve. Italics indicate spinal roots that frequently, but not always, contribute to the nerve.

From	Nerve	Roots	Muscles	Cutaneous
roots	dorsal scapular nerve	C4, C5	rhomboid muscles and levator scapulae	-
roots	long thoracic nerve	C5, C6, C7	serratus anterior	-
upper trunk	nerve to the subclavius	C4, C5, C6	subclavius muscle	-
upper trunk	suprascapular nerve	C4, C5, C6	supraspinatus and infraspinatus	-
lateral cord	lateral pectoral nerve	C5, C6, C7	pectoralis major (by communicating with the medial pectoral nerve)	-
lateral cord	musculocutaneous nerve	C5, C6, C7	coracobrachialis, brachialis and biceps brachii	becomes the lateral cutaneous nerve of the forearm
lateral cord	lateral root of the median nerve	C6, C7	fibres to the median nerve	-
posterior cord	upper subscapular nerve	C5	subscapularis (upper part)	-
posterior cord	thoracodorsal nerve (middle subscapular nerve)	C6, C7, C8	latissimus dorsi	-
posterior cord	lower subscapular nerve	C6	subscapularis (lower part ) and teres major	-
posterior cord	axillary nerve	C5, C6	anterior branch: deltoid 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	C5, C6, C7, C8, T1	triceps brachii, supinator, anconeus, the extensor muscles of the forearm, and brachioradialis	skin of the posterior arm as the posterior cutaneous nerve of the arm
medial cord	medial pectoral nerve	C8, T1	pectoralis major and pectoralis minor	-
medial cord	medial root of the median nerve	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
medial cord	medial cutaneous nerve of the forearm	C8, T1	-	medial skin of the forearm
medial cord	ulnar nerve	C7, C8, T1	flexor carpi ulnaris, the medial two bellies of flexor digitorum profundus, the intrinsic hand muscles except the thenar muscles and the two most lateral lumbricals	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

Some mnemonics for remembering the branches:

• Posterior cord branches
  • STAR - subscapular (upper and lower), thoracodorsal, axillary, radial
  • ULTRA - upper subscapular, lower subscapular, thoracodorsal, radial, axillary
• Lateral Cord Branches
  • LLM "Lucy Loves Me" - lateral pectoral, lateral root of the median nerve, musculocutaneous
• Medial Cord Branches
  • MMMUM "Most Medical Men Use Morphine" - medial pectoral, medial cutaneous nerve of arm, medial cutaneous nerve of forearm, ulnar, medial root of the median nerve

Additional images

Mind map showing branches of brachial plexus

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  Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries.

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  The axillary artery and its branches.

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  Cutaneous nerves of right upper extremity.

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  Diagram of segmental distribution of the cutaneous nerves of the right upper extremity.

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  The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses.

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  Side of neck, showing chief surface markings.

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  Brachial plexus with areas of roots, trunks, divisions and cords marked.

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  Color-coded diagram of brachial plexus illustrating roots of associated nerves.

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  Dissection of brachial plexus

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  Brachial plexus

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  Brachial plexus

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  Brachial plexus

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  Brachial plexus

• Love Me Latha (LML)-(Lateral cord branches) - Lateral pectoral nerve, Musculocutaneous nerve, Lateral root of Median Nerve.
• Union of 4 Medials - (Medial cord branches) - Ulnar nerve, Medial cutaneous nerve of arm, Medial cutaneous nerve of forearm, Medial pectoral nerve, Medial root of Median Nerve.
• RATS- (Posterior cord branches) - Radial nerve, Axillary nerve, Thoracodorsal nerve, Subscapular (Upper & Lower)nerve.
• ULNAR- (Posterior cord branches) - Upper subscapular nerve, Lower subscapular nerve,Nerve to lattissimus dorsi, Axillary nerve, Radial nerve.

See also

• Brachial plexus injury
• Anesthesia of the brachial plexus (concerning nerve blocks for surgical procedures)

Dissection videos

• Learn to draw brachial plexus - Medchrome
• Video of the dissected axilla and Brachial Plexus

External links

• Brachial Plexus and its injury
• lesson3brachialplexus at The Anatomy Lesson by Wesley Norman (Georgetown University)
• Tutorial at Newcastle University
• Blog about Brachial Plexus Injury
• Brachial Plexus Injury/Illustration, Cincinnati Children's Hospital Medical Center
• Learn the Brachial Plexus in Five Minutes or Less by Daniel S. Romm, M.D. and Dennis A. Chu Chu, M.D. [1]
• Brachial Plexus Injury/Illustration, Cincinnati Children's Hospital Medical Center