Brachial nerve plexus


The brachial nerve plexus is created by the anterior rami of the cervical nerve #5 through the thoracic nerve # 1. Additional contributions of various fibers are give out by Cervical 4 and thoracic 2. The brachial plexus can be located just off of the final four cervical vertebrates and the first thoracic vertebrate. The brachial plexus emerges, and then heads off in the lateral but downward direction skirting the first rib behind the clavicle where it finds the axilla. The shoulder and neck muscles, as well as the entire limb of the corresponding side, receive their innervation in this manner.


The brachial plexus is divided into various elements, including roots, division, cords, and trunks. The anterior rami that initially belong to the cervical nerves continue on to create the roots of the brachial plexus. The anterior rami of the cervical nerves # 5 and 6 then conjoin to create the superior trunk. The middle trunk is nothing more than cervical nerve rami #7, and then ventral rami associated with cervical nerve #8 and thoracic nerve #1 join together as they make up the inferior trunk. These three trunks don’t stay together long, as they soon branch off to create the anterior and posterior division.


The three cords are comprised of the unification of the three cords. The upper, middle, and lower trunks come together to make up the posterior cord with their posterior divisions. This means that technically, it is created by fibers that originated within cervical nerve # 5 through cervical nerve #8. The medial cord, which ultimately contains fibers that originate from the cervical nerve #5 through the cervical nerve #7, is the result of the converging anterior fibers of the upper and middle trunk. Obviously, nerve fibers from the anterior branches of the cervical nerves # 5 through the thoracic nerve # 1 end up creating the brachial plexus. Nerve fibers from thoracic 2 and cervical 4 occasionally help out.


Brachial Plexus
Image: Brachial Plexus

The anterior rami continue on to create the roots. The roots then come together to form the basis for trunks and trunks eventually turn into branched divisions. The branched divisions lead to cords and then the cords yield the nerve fibers that are necessary for innervating the upper extremities. It is simply long fibers that go through stages to reach their final destination.

The 3 cords which create the brachial plexus in turn create the five major nerves which serve the coetaneous and muscle requirements of the upper extremities. These five nerve include the radial nerve, the ulna nerve, the median nerve, the axillary nerve, and the musculo-coetaneous nerve.

The posterior cord yields the axillary nerve, which grants the shoulder joint and the skin of the shoulder sensory innervation. It also innervates the teres minor and deltoid muscles with motor sensory capacities. The posterior cord also yields the radial nerve. This nerve is responsible for innervation of the radial portion of the forearm, after extending along the posterior aspect of the brachial region.

The skin of the posterior later surface of the appropriate upper extremity receives sensory impulses while motor fibers innervate the extensor muscles of the elbow joint, the muscle responsible for flexing the elbow joint ( brachioradialis,) and the supinator muscle which is responsible for supinating the forearm and the hand. All innervation of this joint extends into the hand.


The lateral cord yields the musculo-coetaneous nerve. The posterior lateral surface of the arm receives sensory fibers and the anterior muscles of the brachium receive motor fibers. The ulna nerve, which is derived from the medial cord, innervates the skin along the medial 1/3 of the hand. The two main muscles of the forearm and the hand’s intrinsic muscles receive their motor innervation from this nerve. The thumb, however, receives its own motor fibers. The medial cord yields the median nerve. The skin along the radial section of the hand’s palm receives its innervation regarding sensory relations from this nerve. The thumb muscles ( thenar muscles) and the hand muscles are innervated along with the vast majority of the flexor muscles of the forearm by this nerve.
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