The Innervation of the Upper Limb

I've decided to republish this article in a more humane form. Enjoy.
The Innervation of the Upper Limb

The Innervation of the Heart

The article I've written about the cardiac innervation was too long to fit in this blog, so I uploaded it to my GoogleDocs instead, and posted the link to it.

The Innervation of the Heart article

Innervation of the Upper Limb

I have written this short segment about the innervation of the upper extremity, just as a reference to the nerves, their origin, course and what they innervate.

The upper extremity receives neural branches from various spinal nerves. Mostly is innervated by Brachial plexus (C5-T1), but also from Cervical plexus (C3-C4) and intercostal nerve.

CUTANEOUS NERVES OF UE (Upper Extremity)

Supraclavicular nerves:

                The nerves originate from cervical plexus (C3-C4).

From segments C3, C4 (cervical plexus) passes Supraclavicular nerves to clavicle, than go immediately deep to platysma. Platysma is a platelike muscle in the neck extending to the lower face with origin from the subcutaneous layer and fascia covering the M.pectoralis major and M.deltoideus at the level of the first or second rib, with insertion to the mandibula sternae. Those nerves supply skin over clavicle and superolateral aspect of M.pectoralis major.

N.cutaneus brachii sup.lat.:

The nerve originates from terminal branches of N.axillaris (C5-C6)  and emerges from beneath posterior margin of M.deltoideus and supplies skin over lower part of this muscle and on lateral side of midarm.

N.cutaneus brachii inf.lat.:

The nerve originates form N.radialis (C5-C6) (or N.cutaneus post.) and perforates lateral head of triceps, passig close to V.cephalica to supply skin over inferolateral aspect of the arm.

N.cutaneus brachii post.:

The nerve originates from N.radialis (in axilla) (C5-C8) and crosses posterior to and communicates with N.intercostalis brachialis and supplies skin on posterior arm as far as olecranon.

N.cutaneus antebrachii post.:

The nerve originates from N.radialis (C5-C8) (with N.cutaneus inf.lat. of the arm) and perforates the lateral head of triceps, descends laterally in the arm, then runs along and supplies posterior forearm to wrist.

N.cutaneus antebrachii lat.:

The nerve originates form N.musculocutaneus (C6-C7) (terminal branch) and emerges lateral to biceps tendon deep to V.cephalica, supplying skin of anterolateral forearm to wrist.

N.cutaneus antebrachii med.:

The nerve originates from the Truncus medii of the brachial plexus (C8-T1) (in axilla) and descends medial to A.brachialis, pierces fascia profundis with V.basilica in midarm, dividing into anterior and posterior branches that enter forearm and supply the skin of anteromedial aspect to wrist.

N.cutaneus brachii med.:

The nerve originates from Truncus medii of the brachial plexus (C8-T2) (in axilla) amd communicates with N.intercostalis brachialis, continuing to supply the skin of medial aspect of distal arm.

N.intercostalis brachialis:

The nerve originates from second N.intercostalis (as its lateral cutaneous branch) (T2) and extends laterally, communicating with N. cutaneus post. and med. of the arm, supplying the skin of the axilla and medial aspect of proximal arm.

PLEXUS BRACHIALIS

N.dorsalis scapulae:

The nerve originates from posterior aspect of anterior ramus of C5 with frequent contribution form C4

N.dorsalis scapulae pierces the M.scaleneus med. and descends deep to M.levator scapulae and M.rhomboideus

N.dorsalis scapulae innervates M.rhomboideus and also occasionally supplies M.levator scapulae.

N.thoracicus longus:

                The nerve originates from  posterior aspect of anerior rami of C5, C6 and some C7.

N.thoracicus longus passes through cervico-axillary canal, descending posterior to C8 and T1 roots of plexus (anterior rami) and runs inferiorly on superficial surface of the M.serratus ant.

                N.thoracicus longus innervates M.serratus ant.

N.suprascapularis:

                The nerve originates from Truncus sup., receiving fibers from C5, C6 and often C4.

N.suprascapularis passes laterally across lateral cervical region (posterior triangle of neck), superior to brachial plexus and then through scapular notch inferior to superior Lig. transversarium scapularis.

                N.suprascapularis innervates M.supraspinatus and M.infraspinatus also glenohumeral joint.

N.subclavius:

                The nerve originates from Truncus sup., receiving fibers from C5, C6 and often C4.

N.subclavius descends prosterior to clavicle and anterior to brachial plexus and A.subclavia often giving an accessory root to N.phrenicus.

N.subclavius innervates M.subclavius and sternoclavicular joint (accessory phrenic root innervates diaphragm).

N.pectoralis lat.:

                The nerve originates from the side branch of the lateral cord, receiving fibers from C5, C6, C7.

N.pectoralis lat. piercers costocoracoid membrane to reach deep surface of pectoral muscles; a communicating branch to the medial pectoral nerve passes anterior to A. and V.axillaris.

N.pectoralis lat. primarily innervates M.pectoralis major, but some lateral pectoral nerve fibers pass to M.pectoralis minor via branch to medial pectoral nerve.

N.musculocutaneus:

                The nerve originates from the terminal branch of lateral cord, receiving fibers from C5, C6, C7.

N.musculocutaneus exits axilla by piercing M.coracobrachialis, then descends between M.biceps brachii and M.brachialis, supplying both and then continues as N.cutaneus lat. of forearm.

M.musculocutaneus innervates muscles of anterior compartment of arm (M.coracobrachialis, M.biceps brachii and M.brachialis) and skin of lateral aspect of the forearm.

N.medianus:

The lateral root of N.medianus is a terminal branch of lateral cord (C6, C7), medial root of N.medianus is a terminal branch of medial cord (C8, T1).

The lateral and medial root merge to form N.medianus lateral to A.axillaris; N.medianus descends through arm adjacent to A.brachialis, with nerve gradually crossing anterior to artery to lie medial to artery in the cubital fossa.

N.medianus innervates muscles of anterior compartment (except for M.flexor carpi ulnaris and the ulnar half of the M.flexor digitorum profundus), five intrinsic muscles in thenar half of palm and palmar skin.

N.pectoralis med.:

                The nerve originates from side branches of medial cord, receiving fibers from C8, T1.

N.pectoralis med. passes between A. and V.axillaris, then pierces M.pectoralis minor and enters deep surface of M.pectoralis major; although it is called medial for its origin from medial cord, it lies lateral to N.pectoralis lat.

N.pectoralis med. innervates M.pectoralis minor and sternocostal part of M.pectoralis major.

N.cutaneus brachii med.:

                The nerve originates from side branches of medial cord, receiving fibers from C8, T1.

N.cutaneus brachii med. is the smallest nerve of plexus and runs along medial side of V.axillaris and brachialis; the nerve communicates with N.intercostalis brachialis.

N.cutaneus brachii med. innervates the skin of medial side of arm, as far distal as epicondylus medialis humeri and olecranon.

N.cutaneus antebrachii med.:

                The nerve originates from side branches of medial cord, receiving fibers from C8, T1.

N.cutaneus antebrachii med. initially runs with N.ulnaris but pierces deep fascia with V.basilica and enters subcutaneus tissue, dividing into anterior and posterior branches.

N.cutaneus antebrachii med. innervates the skin of medial side of forearm, as far distal as wrist.

N.ulnaris:

                The nerve originates from larger terminal branch of medial cord, receiving fibers from C8, T1.

N.ulnaris descends in medial arm, passes posterior to epicondylus medialis humeri, then descends ulnar aspect of forearm to hand.

N.ulnaris innervates M.flexor carpi ulnaris and the ulnar half of M.flexor digitorum profundus, most M.interossei and M.lumbricales, skin of hand medial to axial line of digit 4.

N.subscapularis sup.:

                The nerve originates from the side branch of posterior cord, receiving fibers from C5.

                N.subscapularis sup. passes posteriorly, entering subscapularis directly.

                N.subscapularis sup. innervates the superior portion of M.subscapularis.

N.subscapularis inf.:

                The nerve originates from the side branch of posterior cord, receiving fibers from C6.

                N.subscapularis inf. passes inferolaterally, deep to A. and V.subscapularis.

                N.subscapularis inf. innervates inferior portion of M.subscapularis and M.teres major.

N.thoracodorsalis:

The nerve originates from the side branch of the posterior cord, receiving fibers from C6, C7, C8.

N.thoracodorsalis arises between N.subscapularis sup. and inf. and runs inferolaterally along posterior axillary wall to apical part of M.latisimus dorsi.

                N.thoracodorsalis innervates M.latisimus dorsi.

N.axillaris:

                The nerve originates from terminal branch of posterior cord, receiving fibers from C5, C6.

N.axillaris exits axillary fossa posteriorly, passing through quadrangular space (bounded superiorly by M.subscapularis, caput humeri and M.teres minor; inferiorly by the M.teres major; medialy by the M.triceps caput longum; laterally by the M.coracobrachialis and collum chirurgicum humeri) with A.circumflexa humeri post., and then winds around collum chirurgicum humeri deep to M.deltoideus.

N.axillaris innervates glenohumeral joint, M.teres minor and M.deltoideus, and skin of superolateral arm (over inferior part of M.deltoideus).

N.radialis:

The nerve originates from larger terminal branch of posterior cord (largest branch of plexus), receiving fibers from C5, C6, C7, C8, T1.

N.radialis exits axillary fossa posterior to A.axillaris, passes posterior to humerus in radial groove with deep A.brachialis, between caput mediale and laterale musculi tricepitis brachii; perforates septum intermusculare brachii laterale, enters fossa cubiti, dividing into N.radialis profundus and superficialis.

N.radialis innervates all muscles of posteriot compartments of arm and forearm, skin of posterior and inferolateral arm, posterior forearm, and dorsum of hand lateral to axial line of digit 4.