Brachial Plexus (and the story of Armmu)

The brachial plexus is a network of somatic nerves formed by the anterior rami of C5-8 and part of the anterior ramus of T1. It originates from the neck and passes laterally over the first rib and down into the axilla. Major nerves innervating the upper limb originates from the brachial plexus. The nerves are posterior to the subclavian artery proximally and surrounds the axillary artery more distally.

The Brachial plexus can be divided into roots, trunks, divisions, cords and terminal nerves or branches as we move more distally.

The roots emerge from the spinal chord, and enter the posterior triangle of the neck through the anterior and middle scalenes. The roots then form the superior, middle and inferior trunks. C5 and C6 join to form the superior trunk, C7 forms the middle trunk and C8 and T1 form the inferior trunk.

Each trunk then devides into anterior and posterior divisions. The anterior divisions contain nerves associated with the anterior part of the arm (including most muscles controlling flexion) and the posterior divisions contain nerves involved in the posterior part (including most muscles controlling extension.)

The divisions join to form three cords, which are named by their positions relative to the axillary artery. The lateral cord is formed by the anterior divisions of the superior and middle trunks, the medial cord is formed by the anterior division of the inferior trunk and the posterior cord is formed by the union of all the posterior divisions.

Finally, these cords form the Musculocutaneous, Median, Axillay, Radial and Ulna nerves. The median nerve is formed by nerves from the lateral and medial cords.

Smaller nerve branches

A number of other smaller nerve branches branch off different sections of the brachial plexus.

Roots:

Dorsal Scapular (C5)

Contribution to phrenic nerve (C5)

Long thoracic nerve (C 5,6,7)

Trunks

Superior: suprascapular and subclavius

Cords

Lateral: Lateral pectoral nerve

Posterior: Superior subscapular nerve, inferior subscapular nerve, and thoracodorsal

Medial: Medial pectoral, Medial cutaneous nerve of the arm, medial cutaneous nerve of the forearm.

Drawing and learning the Brachial plexus

How to Draw the Brachial Plexus



The family tree of ARMMU the armadillo

 

ARMMU the armadillo is descended from a long line of armadillos. His great granddad 'dorsal scapular' married the daughter of a long line of 'long thoracics' who were known for being flight engineers.* From there, they had a son, 'suprascapular'. 


Suprascapular took a spectacular armadillo wife called subclavius, and together they had 2 sons. The eldest- 'superior subscapular', and the younger 'inferior subscapular'. And finally, in an accident they conceived their baby daughter 'thoracodorsal' , whom they named after her grandparents dorsal scapular and long thoracic. 


The two brothers and the baby girl had 2 pairs of distant cousins. The two woodpecker sisters lateral and medial pectoral and the medial cutaneous brothers one who lived in arm, and the other in forearm. In a complicated relationship between these familys, armmu was born in his home the armpit. 


Armmu now works as a anatomy teacher, but often goes off on tangents about his family history. 
*they were famous for inventing and maintaining winged scapulars.