Brachial plexus
is an important topic in Anatomy. It is also important from the examination point of view. I will cover it briefly in this post, but please go back and read from the standard textbook for greater detail.- A plexus is a network of branching nerves. The brachial plexus is a network of nerves that innervates the upper limb
- The brachial plexus consists of roots, trunks, divisions and cords
- The anterior primary rami of five roots namely C5, C6, C7, C8 and T1 are involved in the formation of the brachial plexus
- The plexus consists of three trunks - upper (union of C5 and C6), middle (only C7) and lower (union of C8 and T1)
- Six divisions - Each trunk further divides into an anterior and posterior division
- Three cords - Lateral (fusion of anterior divisions of upper and middle trunk), medial (arises from the anterior division of the lower trunk), posterior (fusion of the posterior divisions of all three trunks).
- The cords continue downwards to become the main nerve trunks of the upper limb
- The roots, trunks and divisions of the brachial plexus lie deep in the posterior triangle of the neck while the cords are located in the axilla
- Injuries to the upper part of the brachial plexus involving the C5 and C6 roots may occur in birth injury or in adults following a fall on the shoulder. The resultant condition is termed Erb-Duchenne palsy in which the position of the hand is similar to a waiter hinting at a tip.
- Injuries to the lower part of the brachial plexus may affect the T1 nerve leading to paralysis of the small muscles of the hand. The hand assumes a clawed appearance (Klumpke's paralysis).
- Occasionally the lower trunk of the plexus may be injured by a cervical rib resulting in paresthesia along the medial border of the arm and wasting of small muscles of the hand
Learn the nerve distribution of the roots, trunks and cords of the brachial plexus. Illustrate your answer with diagram of the brachial plexus.
