The brachial plexus is a network of nerves formed in the neck by the union of the anterior rami of C5-T1 spinal nerves. It divides into roots, trunks, divisions, and cords that provide motor and sensory innervation to the upper limb. The document describes the anatomy and components of the brachial plexus in detail, including its roots, trunks, divisions formed and the three cords (medial, lateral, posterior) and their relationships with the axillary artery.

1. Brachial Plexus
Dr. Naveed Khalid Tarar

2. BRACHIAL PLEXUS
 At the root of the neck, the nerves form a complicated
plexus called the brachial plexus
 The brachial plexus is formed in the posterior triangle of the
neck by the union of the anterior rami of the 5th, 6th, 7th,
and 8th cervical and the 1st thoracic spinal nerves

6. DIVISION OF BRACHIAL PLEXUS
 The plexus can be divided into roots, trunks, divisions, and cords

7. ROOTS
 The roots of the brachial plexus are the anterior rami of C5 to C8, and
most of T1
 The roots and trunks enter the posterior triangle of the neck by
passing between scalene muscles and lie superior and posterior to
the subclavian artery

8. TRUNKS
The three trunks of the brachial plexus originate from the roots,
pass laterally over rib I, and enter the axilla
 The superior trunk
 The middle trunk
 The inferior trunk

9. SUPERIOR TRUNK
 The superior trunk is formed by the union of C5 and C6 roots

10. MIDDLE TRUNK
 The middle trunk is a continuation of the C7 root

11. INFERIOR TRUNK
 The inferior trunk is formed by the union of the C8 and T1 roots
 The inferior trunk lies on rib I posterior to the subclavian artery
 The middle and superior trunks are more superior in position

12. DIVISIONS
Each of the three trunks of the brachial plexus divides into 2
divisions
 Anterior and
 Posterior division

13. ANTERIOR DIVISION
 Three anterior divisions form parts of the brachial plexus that ultimately
give rise to peripheral nerves associated with the anterior compartments
of the arm and forearm

14. POSTERIOR DIVISION
 Three posterior divisions combine to form parts of the brachial plexus
that give rise to nerve associated with the posterior compartments
 No peripheral nerves originate directly from the divisions of the
brachial plexus

16. CORDS
 The three cords of the brachial plexus originate from the
divisions and are related to the second part of the axillary
artery

17. LATERAL CORD
 Lateral cord results from the union of the anterior
divisions of the upper and middle trunks and therefore
has contributions from C5 to C7
 It is positioned lateral to the second part of the axillary
artery

18. MEDIAL CORD
 Medial cord is medial to the second part of the axillary artery
 It is the continuation of the anterior division of the inferior trunk
 It contains contributions from C8 and T1

19. POSTERIOR CORD
 Posterior cord occurs posterior to the second part of
the axillary artery
 It originates as the union of all three posterior divisions.
 It contains contributions from all roots of the brachial plexus
(C5 to T1).

21. BRANCHES
 Branches of the roots
 Branches of the trunks
 Branches of the lateral cord
 Branches of the medial cord
 Branches of the posterior cord

24. RELATIONSHIP OF CORDS
WITH AXILLARY ARTERY
 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
 The lateral cord lies on the lateral side of the second part of the artery.