The medial antebrachial cutaneous nerve forms as a branch of the medial cord from nerve roots C8-T1. This article will focus on the branches of the brachial plexus that deal specifically with the forearm. The brachial plexus is divided into five sections as it courses distally five nerve roots, three trunks, six divisions, three cords, and finally into five branches. The brachial plexus derives from the ventral rami of spinal nerves C5 through T1. The brachial plexus carries the majority of the innervation to the forearm however, a small amount of sensory innervation comes from the medial antebrachial cutaneous nerve. The drainage from the upper limb mainly travels to the lateral nodes, also known as the brachial and humeral nodes.

There are five groups of axillary lymph nodes central, lateral, posterior, anterior, and apical nodes. The majority of lymphatic drainage from the upper limb drains into the axillary lymph nodes.

The blood supply to the nerves in the forearm comes from the vessels that course nearest each nerve. The basilic vein drains into the axillary vein. The radial and ulnar veins drain into the basilic vein. The cephalic vein meets the axillary vein forming the subclavian vein. The cephalic vein gives the median cubital vein branch, which unites with the basilic vein. The venous drainage of the forearm is via the cephalic, basilic, radial, and ulnar veins. The ulnar artery branches into the anterior ulnar recurrent, posterior ulnar recurrent, common interosseous, and muscular branches. After the ulnar artery branches off the brachial artery, it travels under the ulnar head of the pronator teres lateral to the adjacent ulnar nerve. The radial artery gives off the radial recurrent and muscular branches distally. After the radial artery branches from the brachial artery, it travels over the pronator teres muscle lateral to the flexor carpi radialis. The radial artery is lateral, and the ulnar artery is medial. These two arteries branch from the brachial artery just below the antebrachial fossa. The radial and ulnar arteries supply most of the blood to the forearm. The branches from these four main nerves are the anterior interosseus, posterior interosseus, lateral cutaneous nerve of the forearm, deep branch of radial nerve, superficial branch of radial nerve, dorsal cutaneous branches of the ulnar and median nerves, and palmar cutaneous branches of the median and ulnar nerves. All contribute to the innervation of the forearm except the axillary nerve. The five branches of the brachial plexus are the musculocutaneous, axillary, median, ulnar, and radial nerves. The nerves in the forearm derive from branches of the brachial plexus and the medial antebrachial cutaneous nerve. Muscular components in the posterior compartment of the forearm are the brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extensor indicis, and supinator. Muscular components in the anterior compartment of the forearm are the pronator teres, flexor carpi radialis, flexor carpi ulnaris, palmaris longus, flexor digitorum superficialis, flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. A fibrous syndesmosis joint connects the radius and ulna and divides the forearm into anterior flexor and posterior extensor compartments. The four main joints of the forearm are the humeroulnar, humeroradial, and proximal and distal radioulnar joints. The forearm is composed of the radius bone laterally and the ulna bone medially. The nerves of the forearm are complex due to the various nerve branches and the muscles that reside in the upper extremities.

Forearm compartments