The Brachial Plexus Explained
Nerve Spaghetti

The Brachial Plexus

MF Dauzvardis

Structure of the Human Body

Objectives

Draw it--damnit!

Major components--Robert Taylor drinks cold beer

• Roots

• Trunks

• Divisions

• Cords

• Branches

Key branches of axillary artery

Details on branches from the roots, trunks, and cords

Clinical Correlates

Self-assessment goodies

 Objectives:

• Be able to draw the brachial plexus in your sleep

• Learn to identify the roots, trunks, divisions, cords, and individual

branches by using the interactive images

• Link the various terminal branches with their specific origins and spinal root components

• Equate the various major plexus related traumas with their specific site of injury

What is the Brachial Plexus?

Draw it--Damnit

https://www.youtube.com/watch?v=Na_8DwmXWhE&feature=c4-overview&list=UUbiT_O6nJrIlc8JDa_78bsw

MAJOR COMPONENTS

ROBERT TAYLOR DRINKS COLD BEER (axillary nerve not included in drawing)

Major branches of the axillary artery

Computer enhanced radiographic image of the axillary artery

BRANCHES ORIGINATING FROM THE ROOTS

BRANCHES ORIGINATING FROM THE TRUNKS

BRANCHES OF THE LATERAL CORD

BRANCHES FROM THE MEDIAL CORD

BRANCH FORMED BY THE UNION OF THE LATERAL AND MEDIAL CORDS

Union of lateral and medial heads of the median nerve to form the MEDIAL NERVE

Branches formed by the posterior cord

Clinical Correlates

Major injuries of the brachial plexus and terminal branches

Images of injuries

More images of nerve lesions; Note that the true ulnar claw as seen in the first and second pictures is caused by a distal ulnar lesion which paralyzes the medial two lumbricals and may cause thenar wasting due to loss of adductor pollicis. The "pope's blessing" or "Benedictine" sign looks the same but is only visible upon an active attempt to make a fist. It is due to a median nerve injury which paralyzes the lateral 2 lumbricals and weakens the flexor digitorum superficialis and deep. A total claw is visible in the infant's hand and is a result of Klumpke's palsy--damage to the lower roots affects the ulnar, median, and radial nerves--affecting all lumbricals and weakening extension of the digits.A sudden jerking of a child's arm or falling from a tree and grabbing a limb can cause it. Erb's palsy is a result of upper root damage and affects the suprascapular, musculocutaneous, and axillary nerves. The deltoid, brachialis, biceps, supraspinatus, and infraspinatus muscles may be affected contributing to the "waiter's tip" sign. Dystocia can cause both Klumpke's and Erb's palsies.

Review questions 

Nice pictures of various parts of the brachial plexus (dissected and photographed by Lauren Fetty) 

Nice roots:

Nice divisions:

Nice "M"

Some nice practical questions:

Match this!

Match more!!!

Moron dermatomes

A dermatome is a sensory band served by one dorsal root. Named cutaneous nerves may come from several dorsal roots and innervate a larger patch of skin.

Good mnemonic for remembering root contribution to marmu (musculocutaneous, axillary, radial, median, and ulnar nerves)

Three musketeers assassinated 5 rats, 5 mice, and 2 unicorns

Link to Lumen Learn'em brachial plexus.

Robert Taylor went home------The end