1. Brachial plexus
The brachial plexus is a somatic plexus for
med by the anterior rami ofC5,6,7,8 and T
1.
It originates in the neck, passes laterally a
nd inferiorly over the (1) rib, and enters t
he axilla.
2.
3. Roots
The roots of the brachial plexus are the a
nterior rami of C5 to C8, and most of T1.
The roots and trunks enter the posterior t
riangle of the neck by passing between th
e anterior scalene and middle scalene mu
scles and lie superior and posterior to the
subclavian artery
4.
5. Trunks
The three trunks of the brachial plexus ori
ginate from the roots, pass laterally over r
ib I, and enter the axilla :
>The superior trunk is formed by the unio
n of C5 and C6 roots;
>The middle trunk is a continuation of the
C7 root;
>The inferior trunk is formed by the union
of the C8 and T1 roots.
6.
7. Divisions
Each of the three trunks of the brachial plexus di
vides into an anterior and a posterior division:
>the three anterior divisions form parts of the br
achial plexus that ultimately give rise to peripher
al nerves associated with the anterior compartm
ents of the arm and forearm;
>the three posterior divisions combine to form p
arts of the brachial plexus that give rise to nerves
associated with the posterior compartments.
8.
9. Cords
The three cords of the brachial plexus originate from th
e divisions and are related to the second part of the axill
ary artery.
➤lateral cord results from the union of the anterior divi
sions of the upper and middle trunks and therefore has
contributions from C5 to C7.
➤medial cord is the continuation of the anterior
division of the inferior trunk-it contains contributions fr
om C8 and T1.
➤posterior cord originates as the union of all three pos
terior divisions-it contains contributions from all roots o
f the brachial plexus (C5 to T1).
