What are the branches of the brachial plexus?
The brachial plexus is a complex network of nerves that originates from the lower spine and extends into the upper limb, providing motor and sensory innervation to the shoulder, arm, and hand. Understanding the branches of the brachial plexus is crucial for diagnosing and treating various conditions affecting the upper limb, such as nerve injuries, tumors, and infections. In this article, we will explore the different branches of the brachial plexus and their functions.
1. The Root Level
The brachial plexus is formed by the ventral rami (roots) of the lower four cervical nerves (C5, C6, C7, and C8) and the first thoracic nerve (T1). These roots merge to form three trunks: superior, middle, and inferior.
2. The Trunk Level
The superior trunk is formed by the union of the C5 and C6 roots. It divides into two divisions: the lateral and posterior divisions. The lateral division gives rise to the lateral cord, while the posterior division contributes to the posterior cord.
The middle trunk is derived from the C7 root and splits into two divisions: the anterior and posterior divisions. The anterior division joins the lateral cord to form the lateral cord, while the posterior division joins the posterior cord to form the posterior cord.
The inferior trunk is formed by the C8 and T1 roots and divides into two divisions: the anterior and posterior divisions. The anterior division joins the lateral cord to form the lateral cord, while the posterior division joins the posterior cord to form the posterior cord.
3. The Cord Level
The lateral cord is formed by the union of the superior and middle trunks. It gives rise to three branches: the musculocutaneous nerve, the lateral pectoral nerve, and the lateral cutaneous nerve of the arm.
The posterior cord is formed by the union of the superior and inferior trunks. It gives rise to three branches: the axillary nerve, the radial nerve, and the posterior cutaneous nerve of the arm.
The medial cord is formed by the union of the middle and inferior trunks. It gives rise to three branches: the ulnar nerve, the medial pectoral nerve, and the medial cutaneous nerve of the arm.
4. The Nerve Level
The branches of the brachial plexus further divide into peripheral nerves that innervate specific muscles and skin areas. Some of the key nerves include:
– Musculocutaneous nerve: Supplies the biceps brachii, brachialis, and brachioradialis muscles, as well as the skin over the antecubital fossa.
– Radial nerve: Innervates the triceps brachii, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, and extensor digiti minimi muscles, as well as the skin over the posterior aspect of the forearm and hand.
– Ulnar nerve: Supplies the flexor carpi ulnaris, flexor digitorum profundus, flexor digitorum superficialis, and flexor pollicis longus muscles, as well as the skin over the medial aspect of the forearm and hand.
– Median nerve: Innervates the flexor carpi radialis, flexor digitorum superficialis, flexor pollicis longus, and the muscles of the anterior compartment of the forearm, as well as the skin over the lateral and anterior aspects of the forearm and hand.
– Axillary nerve: Supplies the deltoid and teres minor muscles, as well as the skin over the deltoid area.
– Ulnar nerve: Innervates the flexor carpi ulnaris, flexor digitorum profundus, flexor digitorum superficialis, and flexor pollicis longus muscles, as well as the skin over the medial aspect of the forearm and hand.
Understanding the branches of the brachial plexus is essential for diagnosing and treating various conditions affecting the upper limb. By recognizing the specific nerves and their functions, healthcare professionals can provide appropriate interventions and improve patient outcomes.
