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-T1). It proceeds through the neck, the axilla (armpit region), and into the arm.

1 Function
2 Anatomy
3 Additional images
4 See also
5 References
6 Dissection videos
7 External links

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. ^[1]

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-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

Specific branches

From	Nerve	Roots	Muscles	Cutaneous
roots	dorsal scapular nerve	C5	rhomboid muscles and levator scapulae	-
roots	long thoracic nerve	C5, C6, C7	serratus anterior	-
upper trunk	nerve to the subclavius	C5, C6	subclavius muscle	-
upper trunk	suprascapular nerve	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	C5, C6, C7	fibres to the median nerve	-
posterior cord	upper subscapular nerve	C5, C6	subscapularis (upper part)	-
posterior cord	thoracodorsal nerve (middle subscapular nerve)	C6, C7, C8	latissimus dorsi	-
posterior cord	lower subscapular nerve	C5, 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	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	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 medial 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

References

^ Moore, K.L., & Agur, A.M. (2007). Essential Clinical Anatomy: Third Edition. Baltimore: Lippincott Williams & Wilkins. 434-435. ISBN 978-0-7817-6274-8

Dissection videos

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

Nerves: spinal nerves (TA A14.2, GA 9.916)

Cervical (8)

C1, C2, C3, C4, C5, C6, C7, C8

anterior (Cervical plexus, Brachial plexus) – posterior (Posterior branches of cervical nerves, Suboccipital – C1, Greater occipital – C2, Third occipital – C3)

Thoracic (12)

T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12

anterior (Intercostal, Intercostobrachial – T2, Thoraco-abdominal nerves – T7–T11, Subcostal – T12) – posterior (Posterior branches of thoracic nerves)

Lumbar (5)

L1, L2, L3, L4, L5

anterior (Lumbar plexus, Lumbosacral trunk) · posterior (Posterior branches of the lumbar nerves, Superior cluneal L1–L3)

Sacral (5)

S1, S2, S3, S4, S5

anterior (Sacral plexus) · posterior (Posterior branches of sacral nerves, Medial cluneal nerves)

Coccygeal (1)

anterior (Coccygeal plexus) · posterior (Posterior branch of coccygeal nerve)

M: PNS

anat(h/r/t/c/b/l/s/a)/phys(r)/devp/prot/nttr/nttm/ntrp

noco/auto/cong/tumr, sysi/epon, injr

proc, drug(N1B)

Nerves of upper limbs (primarily): the brachial plexus (C5–T1) (TA A14.2.03, GA 9.930)

Supraclavicular

root (dorsal scapular, long thoracic) · upper trunk (suprascapular, to the subclavius)

Infraclavicular

lateral cord	lateral pectoral musculocutaneous (lateral cutaneous of forearm) median/lateral root: anterior interosseous · palmar · recurrent · common palmar digital (proper palmar digital)

medial cord	medial pectoral cutaneous: medial cutaneous of forearm · medial cutaneous of arm ulnar: muscular · palmar · dorsal (dorsal digital nerves) · superficial (common palmar digital, proper palmar digital) · deep median/medial root: see above

posterior cord	subscapular (upper, lower) · thoracodorsal axillary (superior lateral cutaneous of arm) radial: muscular · cutaneous (posterior of arm, inferior lateral of arm, posterior of forearm) · superficial (dorsal digital nerves) · deep (posterior interosseous)

Other

cutaneous innervation of the upper limbs