Download Cords of the Brachial Plexus - جامعة الكوفة

‫ مـــاجــســتــير تــشــريــح و‬/ )‫جــــامـعـة الـكــوفـــــة‬/‫مـــنــــقـــــذ مـــازن مـغــــامـس (كلـــــية الطـــــــب‬.‫د‬
‫أنــســجــة‬
Brachial Plexus
‫الضفيرة العصبية العضدية‬
Brachial plexus is a nervous network supplies the upper limb. The roots of this
plexus are the ventral rami of the lower four cervical nerves, the greater part of the
ventral ramus of the first thoracic nerve, and a small twig each from the ventral rami
of the fourth cervical and second thoracic nerves. These roots lie in the posterior
triangle of the neck.
The nerves entering the upper limb provide the following important functions:
sensory innervation to the skin and deep structures, such as the joints; motor
innervation to the muscles; influence over the diameters of the blood vessels by the
sympathetic vasomotor nerves; and sympathetic secretomotor supply to the sweat
glands.
The plexus can be divided into roots, trunks, divisions, and cords (figure -1-).
The roots of C5 and 6 unite to form the upper trunk, the root of C7 continues as the
middle trunk, and the roots of C8 and T1 unite to form the lower trunk. Each trunk
then divides into anterior and posterior divisions. The anterior divisions of the upper
and middle trunks unite to form the lateral cord, the anterior division of the lower
trunk continues as the medial cord, and the posterior divisions of all three trunks join
to form the posterior cord.
The roots, trunks, and divisions of the brachial plexus reside in the lower part
of the posterior triangle of the neck. The cords become arranged around the axillary
artery in the axilla (Fig. -2-). Here, the brachial plexus and the axillary artery and vein
are enclosed in the axillary sheath.
1
Figure -1-: The formation of the main parts of the brachial plexus.
Figure -2-: Arrangement of the cords of brachial plexus around the axillary artery.
2
Cords of the Brachial Plexus:
All three cords of the brachial plexus lie above and lateral to the first part of
the axillary artery (figure -2-). The medial cord crosses behind the artery to reach the
medial side of the second part of the artery. The posterior cord lies behind the second
part of the artery, and the lateral cord lies on the lateral side of the second part of the
artery. Thus, the cords of the plexus have the relationship to the second part of the
axillary artery that is indicated by their names.
Most branches of the cords that form the main nerve trunks of the upper limb
continue this relationship to the artery in its third part (Fig. -3-).
The branches of the different parts of the brachial plexus are as follows (table -1-):

Roots:
1- Dorsal scapular nerve (C5)
2- Long thoracic nerve (C5, 6, and 7)

Upper trunk:
1- Nerve to subclavius (C5 and 6)
2- Suprascapular nerve (supplies the supraspinatus and infraspinatus muscles)

Lateral cord:
1- Lateral pectoral nerve
2- Musculocutaneous nerve
3- Lateral root of median nerve

Medial cord:
1- Medial pectoral nerve
2&3- Medial cutaneous nerve of arm and medial cutaneous nerve of forearm
4- Ulnar nerve
5- Medial root of median nerve
3

Posterior cord:
1&2- Upper and lower subscapular nerves
3- Thoracodorsal nerve
4- Axillary nerve
5- Radial nerve
Figure -3-: Relations of the brachial plexus and its branches to the axillary
artery and vein.
4
Table -1-: Branches of brachial plexus.
Nerve
Dorsal scapular
Long thoracic
Structures Innervated
Rhomboids; occasionally supplies levator scapulae
Serratus anterior
Suprascapular
Supraspinatus and infraspinatus muscles; shoulder joint
nerve to subclavius
Subclavius and sternoclavicular joint
Lateral pectoral
Pectoralis major
Musculo-cutaneous
Muscles of anterior compartment of arm (coracobrachialis, biceps
brachii and brachialis); skin of lateral aspect of forearm
Median
Muscles of anterior forearm compartment (except for flexor carpi
ulnaris and ulnar half of flexor digitorum profundus), five
intrinsic muscles in thenar half of palm and palmar skin
Medial pectoral
Medial cutaneous
nerve of arm
Pectoralis minor and sternocostal part of pectoralis major
Skin of medial side of arm, as far distal as medial epicondyle of
humerus and olecranon of ulna
Median cutaneous
nerve of forearm
Skin of medial side of forearm, as far distal as wrist
Flexor carpi ulnaris and ulnar half of flexor digitorum profundus
Ulnar
(forearm); most intrinsic muscles of hand; skin of hand medial to
axial line of digit 4
Upper subscapular
Superior portion of subscapularis
Lower subscapular
Inferior portion of subscapularis and teres major
Thoracodorsal
Latissimus dorsi
shoulder joint; teres minor and deltoid muscles; skin of
Axillary
superolateral arm (over inferior part of deltoid)
Radial
All muscles of posterior compartments of arm and forearm skin of
posterior and inferolateral arm, posterior forearm, and dorsum of
hand lateral to axial line of digit 4
References:
1. Richard S. Snell (2005): Clinical Anatomy by Regions, 8th. Edition. Chapter 9. Pp.
447-451.
2. Keith L. Moore et al. (2006): Clinically Oriented Anatomy, 5th. Edition. Chapter 6.
Pp. 774-776.
3. GRAY'S Anatomy for students (2007) by Richard L. Drake, Wayne Vogl, and
Adam W.M. Mitchell. Chapter 7. Pp. 656-666.
5