Brachial Plexus and Upper Limb Nerve Supply

The nerve supply of the upper limb is provided by the brachial plexus, which is a network of nerve fibers that supplies the skin and musculature of the upper limb. The brachial plexus begins in the root of the neck, passes through the axilla, and runs through the entire upper extremity. It is formed by the anterior rami (divisions) of cervical spinal nerves C5 to T1. The brachial plexus has five major branches: axillary, musculocutaneous, median, radial, and ulnar nerves.

1. Brachial Plexus: The brachial plexus is a collection of nerve fibers that supply motor and sensory innervation to the upper limb. It originates from nerve roots C5 to T1 and, as it passes through the axilla, merges the nerve fibers from these roots into different nerve branches.

2. Musculocutaneous Nerve (C5-C7): The musculocutaneous nerve is formed by contributions from the lateral cord and provides motor innervation to the biceps brachii, coracobrachialis, and brachialis muscles. Once it gives off its motor fibers in the anterior compartment, the musculocutaneous nerve becomes the lateral antebrachial cutaneous nerve and provides cutaneous innervation to the lateral aspect of the forearm.

3. Median Nerve (C6-T1): The median nerve is formed by contributions from the medial and lateral cords and provides the majority of motor innervation to the musculature in the anterior forearm as well as cutaneous innervation to the lateral 3 1/2 fingers of the palmar hand. The main trunk of the median nerve innervates the pronator teres, flexor carpi radialis, palmaris longus, and flexor digitorum superficialis muscles. The anterior interosseous nerve innervates the flexor pollicis longus, pronator quadratus, and the lateral half of the flexor digitorum profundus.

4. Ulnar Nerve: The ulnar nerve is formed by contributions from the medial cord and provides motor innervation to the muscles of the anterior compartment of the forearm, as well as the thenar muscles and lateral two lumbricals of the hand. For sensory coverage, the ulnar nerve supplies the medial aspect of the hand and the ulnar side of the forearm.

5. Radial Nerve: The radial nerve is formed from nerve fibers from all the roots of the brachial plexus and provides motor innervation to the muscles of the posterior compartment of the forearm and the extensor muscles of the hand. The deep branch of the radial nerve innervates the supinator and extensor carpi radialis brevis.

Injury to the brachial plexus can result in motor and sensory palsies affecting the innervated muscles and skin. Upper brachial plexus (Erb's Palsy) and lower brachial plexus (Klumpke's Palsy) are two common variants of brachial plexus damage. The brachial plexus is responsible for the motor innervation of all of the muscles of the upper extremity, with the exception of the trapezius and levator scapula. It also supplies all of the cutaneous innervation of the upper limb, except for the area of the axilla (which is supplied by the supraclavicular nerve) and the dorsal aspect of the hand. The radial nerve is derived from the posterior cord and serves as motor innervation to the deltoid and teres minor muscles. The axillary nerve leaves the brachial plexus at the lower border of the subscapularis muscle and serves as motor innervation to the deltoid and teres minor muscles. The radial nerve continues along the posterior and inferior surface of the axillary artery and wrist. The median nerve is formed by contributions from the medial and lateral cords and provides the majority of motor innervation to the musculature in the anterior forearm as well as cutaneous innervation to the lateral 3 1/2 fingers of the palmar hand. The ulnar nerve is formed by contributions from the medial cord and provides motor innervation to the muscles of the anterior compartment of the forearm, as well as the thenar muscles and lateral two lumbricals of the hand. The radial nerve is formed from nerve fibers from all the roots of the brachial plexus and provides motor innervation to the muscles of the posterior compartment of the forearm and the extensor muscles of the hand. The deep branch of the radial nerve innervates the supinator and extensor carpi radialis brevis. The musculocutaneous nerve is formed by contributions from the lateral cord and provides motor innervation to the biceps brachii, coracobrachialis, and brachialis muscles. Once it gives off its motor fibers in the anterior compartment, the musculocutaneous nerve becomes the lateral antebrachial cutaneous nerve and provides cutaneous innervation to the lateral aspect of the forearm. The median nerve is formed by contributions from the medial and lateral cords and provides the majority of motor innervation to the musculature in the anterior forearm as well as cutaneous innervation to the lateral 3 1/2 fingers of the palmar hand. The ulnar nerve is formed by contributions from the medial cord and provides motor innervation to the muscles of the anterior compartment of the forearm, as well as the thenar muscles and lateral two lumbricals of the hand. The radial nerve is formed from nerve fibers from all the roots of the brachial plexus and provides motor innervation to the muscles of the posterior compartment of the forearm and the extensor muscles of the hand. The deep branch of the radial nerve innervates the supinator and extensor carpi radialis brevis. The musculocutaneous nerve is formed by contributions from the lateral cord and provides motor innervation to the biceps brachii, coracobrachialis, and brachialis muscles. Once it gives off its motor fibers in the anterior compartment, the musculocutaneous nerve becomes the lateral antebrachial cutaneous nerve and provides cutaneous innervation to the lateral aspect of the forearm. The median nerve is formed by contributions from the medial and lateral cords and provides the majority of motor innervation to the musculature in the anterior forearm as well as cutaneous innervation to the lateral 3 1/2 fingers of the palmar hand. The ulnar nerve is formed by contributions from the medial cord and provides motor innervation to the muscles of the anterior compartment of the forearm, as well as the thenar muscles and lateral two lumbricals of the hand. The radial nerve is formed from nerve fibers from all the roots of the brachial plexus and provides motor innervation to the muscles of the posterior compartment of the forearm and the extensor muscles of the hand. The deep branch of the radial nerve innervates the supinator and extensor carpi radialis brevis. The musculocutaneous nerve is formed by contributions from the lateral cord and provides motor innervation to the biceps brachii, coracobrachialis, and brachialis muscles. Once it gives off its motor fibers in the anterior compartment, the musculocutaneous nerve becomes the lateral antebrachial cutaneous nerve and provides cutaneous innervation to the lateral aspect of the forearm. The median nerve is formed by contributions from the medial and lateral cords and provides the majority of motor innervation to the musculature in the anterior forearm as well as cutaneous innervation to the lateral 3 1/2 fingers of the palmar hand. The ulnar nerve is formed by contributions from the medial cord and provides motor innervation to the muscles of the anterior compartment of the forearm, as well as the thenar muscles and lateral two lumbricals of the hand. The radial nerve is formed from nerve fibers from all the roots of the brachial plexus and provides motor innervation to the muscles of the posterior compartment of the forearm and the extensor muscles of the hand. The deep branch of the radial nerve innervates the supinator and extensor carpi radialis brevis. The musculocutaneous nerve is formed by contributions from the lateral cord and provides motor innervation to the biceps brachii, coracobrachialis, and brachialis

This quiz covers the anatomy and function of the brachial plexus, including its nerve branches and their motor and sensory innervations of the upper limb. It also discusses common variants of brachial plexus damage and details the functions of each major nerve branch.