What are the terminal 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. Comprised of the ventral rami of the lower four cervical nerves (C5, C6, C7, and C8) and the first thoracic nerve (T1), the brachial plexus is responsible for the intricate movements and sensations in the upper limb. Among its many branches, the terminal branches of the brachial plexus play a crucial role in the functioning of the hand and forearm. This article will delve into the various terminal branches and their functions.
The terminal branches of the brachial plexus can be categorized into two main groups: the upper and lower trunks. The upper trunk includes the lateral, posterior, and medial cords, while the lower trunk includes the anterior and posterior cords. Each of these cords gives rise to specific terminal branches, which are discussed below.
1. Lateral cord
The lateral cord, which arises from the upper trunk, gives rise to the following terminal branches:
a. Lateral cutaneous nerve of the arm: This nerve innervates the lateral aspect of the arm, providing sensation to the skin.
b. Lateral antebrachial cutaneous nerve: This nerve extends into the forearm, innervating the lateral aspect of the forearm and the dorsum of the hand.
2. Posterior cord
The posterior cord, also originating from the upper trunk, supplies the following terminal branches:
a. Posterior interosseous nerve: This nerve runs down the posterior aspect of the forearm, innervating the muscles of the extensor compartment and providing sensation to the back of the hand and fingers.
b. Median nerve: The median nerve is a major terminal branch of the brachial plexus, arising from the lateral and posterior cords. It innervates the muscles of the anterior compartment of the forearm, as well as the palmar aspect of the thumb, index finger, middle finger, and half of the ring finger. The median nerve also provides sensation to the palmar aspect of the thumb, index finger, middle finger, and half of the ring finger.
3. Medial cord
The medial cord, another upper trunk branch, contributes to the following terminal branches:
a. Median nerve: As mentioned earlier, the median nerve arises from both the lateral and posterior cords and innervates the muscles of the anterior compartment of the forearm, as well as the palmar aspect of the thumb, index finger, middle finger, and half of the ring finger.
b. Ulnar nerve: The ulnar nerve arises from the medial cord and provides motor innervation to the muscles of the flexor compartment of the forearm and the hand. It also provides sensation to the palmar aspect of the little finger and half of the ring finger.
4. Anterior cord
The anterior cord, a branch of the lower trunk, supplies the following terminal branches:
a. Median nerve: As mentioned earlier, the median nerve arises from both the lateral and posterior cords and innervates the muscles of the anterior compartment of the forearm, as well as the palmar aspect of the thumb, index finger, middle finger, and half of the ring finger.
b. Musculocutaneous nerve: The musculocutaneous nerve arises from the anterior cord and innervates the muscles of the anterior compartment of the forearm, including the biceps brachii, brachialis, and coracobrachialis. It also provides sensation to the lateral aspect of the arm.
5. Posterior cord
The posterior cord, another lower trunk branch, contributes to the following terminal branches:
a. Radial nerve: The radial nerve arises from the posterior cord and provides motor innervation to the muscles of the extensor compartment of the forearm and the hand. It also provides sensation to the back of the hand and fingers.
In conclusion, the terminal branches of the brachial plexus are essential for the proper functioning of the upper limb. These branches include the lateral cutaneous nerve of the arm, lateral antebrachial cutaneous nerve, posterior interosseous nerve, median nerve, ulnar nerve, musculocutaneous nerve, and radial nerve. Understanding the roles and functions of these terminal branches is crucial for diagnosing and treating conditions affecting the brachial plexus and its associated nerves.
