Roots, trunks, divisions, cords and branches — recalled by 'Randy Travis Drinks Cold Beer'
Brachial plexus — the five orders of the plexus.
Anatomy · Brain & nerves
Brachial plexus
Roots C5–T1
Peripheral nerves · neck and upper limb
The network of nerves formed from the ventral rami of C5 to T1 that supplies the whole of the upper limb. It begins in the neck between the scalene muscles, passes over the first rib behind the clavicle, and fans out around the axillary artery, finally resolving into five terminal nerves: the musculocutaneous, axillary, radial, median and ulnar. Seen in a picture, it is a yellow Y-shaped tangle that ends as five cables running down the arm.
How to spot them
- ▸A braid of five roots that merge into three trunks, then divide and recombine into three cords
- ▸Runs in the posterior triangle of the neck, between the anterior and middle scalene muscles, then under the collarbone into the armpit
- ▸The lateral and medial cords join in front of the axillary artery to form an 'M' whose centre is the median nerve
- ▸Ends as five large nerves, each with a name and a territory in the arm
What to know
Five terminal nerves emerge from it: musculocutaneous, axillary, radial, median and ulnar
Brachial plexus — its terminal branches.
Between the anterior and middle scalene muscles, then over the first rib and behind the collarbone
Brachial plexus — the path from neck to armpit.
A tumour at the apex of the lung can invade it, causing shoulder pain, wasting of the small hand muscles and a drooping eyelid
Brachial plexus — Pancoast tumour, with Horner's syndrome from the sympathetic chain.
Anaesthetists inject around it above the collarbone or in the neck to numb the entire arm for surgery
Brachial plexus — the interscalene and supraclavicular blocks.
Damage to its long thoracic branch (C5–C7) leaves the shoulder blade sticking out from the back like a wing
Brachial plexus — winged scapula.
Named for the arm, from the Latin for the upper arm; its three cords are named for their position around the axillary artery
Brachial plexus — lateral, posterior and medial cords.
Stretching the arm and neck apart at birth, or in a motorcycle crash, can avulse its roots and leave the arm limp
Brachial plexus — traction injuries such as Erb's and Klumpke's palsy.
Key ideas
- The word 'brachial' is from Latin brachium, arm; a plexus is a braided network of nerves, and this is the archetypal example.
- In a picture it reads from the neck outward: five roots, three trunks, six divisions, three cords and five terminal nerves.
Quick-fire facts
- •Formed from ventral rami of C5, C6, C7, C8 and T1, sometimes with contributions from C4 and T2
- •Stages in order: roots, trunks (upper, middle, lower), divisions (anterior, posterior), cords (lateral, posterior, medial), terminal branches
- •Mnemonic: 'Randy Travis Drinks Cold Beer' — roots, trunks, divisions, cords, branches
- •The five terminal nerves are musculocutaneous, axillary, radial, median, ulnar; the last two are the ones tested most often
- •Named 'cords' for their relation to the second part of the axillary artery
- •Erb's palsy (C5–C6, 'waiter's tip') and Klumpke's palsy (C8–T1, claw hand) are classic injuries
- •The long thoracic nerve (C5–C7) arises from the roots and supplies serratus anterior; its injury gives a winged scapula
- •Regional anaesthesia around it, such as an interscalene block, is a staple of shoulder surgery
- •A Pancoast tumour at the lung apex can invade its lower trunk and roots
Drill it — 7 cards
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Sources
- TeachMeAnatomy — Brachial plexus
- Kenhub — Brachial plexus: Anatomy, branches and mnemonics