Branches of the Brachial Plexus Found in the Axilla
The nerve to the subclavius (C5 and 6) supplies the subclavius
muscle (Figs. 9.15, 9.19, and 9.20). It is important
clinically because it may give a contribution (C5) to the
phrenic nerve; this branch, when present, is referred to as
the accessory phrenic nerve.
The long thoracic nerve (C5, 6, and 7) arises from the
roots of the brachial plexus in the neck and enters the
axilla by passing down over the lateral border of the 1st rib
behind the axillary vessels and brachial plexus (Figs. 9.15
and 9.19). It descends over the lateral surface of the serratus
anterior muscle, which it supplies.
The lateral pectoral nerve arises from the lateral cord of
the brachial plexus and supplies the pectoralis major muscle
(Figs. 9.13 and 9.20).
The musculocutaneous nerve arises from the lateral
cord of the brachial plexus, supplies the coracobrachialis
muscle, and leaves the axilla by piercing that muscle (Figs.
9.13 and 9.20). A summary of the complete distribution of
the musculocutaneous nerve is given in Figure 9.22.
The lateral root of the median nerve is the direct continuation
of the lateral cord of the brachial plexus (Figs.
9.13 and 9.19). It is joined by the medial root to form the
median nerve trunk, and this passes downward on the lateral
side of the axillary artery. The median nerve gives off
no branches in the axilla.
The medial pectoral nerve arises from the medial cord of
the brachial plexus, supplies and pierces the pectoralis minor
muscle, and supplies the pectoralis major muscle (Fig. 9.19).
The medial cutaneous nerve of the arm (T1) arises
from the medial cord of the brachial plexus (Figs. 9.12 and
9.20) and is joined by the intercostobrachial nerve (lateral
cutaneous branch of the 2nd intercostal nerve). It supplies
the skin on the medial side of the arm.
The medial cutaneous nerve of the forearm arises from
the medial cord of the brachial plexus and descends in front The ulnar nerve (C8 and T1) arises from the medial
cord of the brachial plexus and descends in the interval
between the axillary artery and vein (Figs. 9.13 and 9.20).
The ulnar nerve gives off no branches in the axilla. A summary
of the complete distribution of the ulnar nerve is
given in Figure 9.23.
The medial root of the median nerve arises from the
medial cord of the brachial plexus and crosses in front of
the third part of the axillary artery to join the lateral root
of the median nerve (Figs. 9.13 and 9.20). A summary diagram
of the complete distribution of the median nerve is
given in Figure 9.22.
The upper and lower subscapular nerves arise from the
posterior cord of the brachial plexus and supply the upper
and lower parts of the subscapularis muscle. In addition,
the lower subscapular nerve supplies the teres muscle
(Figs. 9.15 and 9.19).
The thoracodorsal nerve arises from the posterior cord
of the brachial plexus and runs downward to supply the
latissimus dorsi muscle (Figs. 9.15 and