Brachial Plexus

Brachial plexus

Innervates most of the muscles moving the upper limb. Intermingling of nerve fibers from the ventral rami of spinal nerves C5 to T1.

Dorsal scapular nerve

Arises from C5 (with a frequent contribution from C4). Innervates the inferior slips of levator scapulae and the rhomboid major and minor muscles.

Divisions

No nerves arise directly from the anterior and posterior divisions

Suprascapular nerve

Arises from C5 and C6 (and sometimes C4). Innervates the supraspinatus and infraspinatus muscles and gives an articular (sensory) branch to the shoulder joint.

Long thoracic nerve

Arises from ventral rami of C5, C6, and C7. Supplies serratus anterior muscle.

M formation

Arrangement of musculocutaneous, median (with its two roots), and ulnar nerves anterior to the axillary artery.

Nerve to subclavius

C5, C6. Innervates the subclavius muscle.

Upper subscapular nerve

C5-C6. Innervates part of the subscapularis muscle.

Lower subscapular nerve

C5-C6. Innervates teres major and subscapularis muscles

Axillary nerve

C5-C6. Innervates the deltoid and teres minor muscles. Supplies the shoulder joint and skin over the inferior half of the deltoid and adjacent arm. One of two terminal branches of the posterior cord

Lateral cord

C5-C7. Formed from the anterior divisions of the superior and middle trunks. Gives rise to lateral pectoral nerve, musculocutaneous nerve, lateral root of the median nerve

Lateral pectoral nerve

C5-C7. Innervates pectoralis major muscle (clavicular head).

Musculocutaneous nerve

C5-C7. Innervates the three flexor muscles in the arm and supplies the elbow joint and skin on the lateral side of the forearm. One of two terminal branches of the lateral cord.

Lateral root of the median nerve

C5-C7. The other terminal branch of the lateral cord. Joined by a contribution from the medial cord to form the median nerve.

Posterior cord

C5-T1. Formed from the posterior divisions of all three trunks. Five nerves arise directly from the posterior cord: upper subscapular nerve, thoracodorsal nerve, lower subscapular nerve, axillary nerve, radial nerve.

Median nerve

C5-T1. Innervates 6&1/2 muscles of the flexor forearm and five intrinsic muscles of the hand. Supplies the elbow and wrist joints and the skin of most of the palmar surface of the hand.

Radial nerve

C5-T1. The other terminal branch of the posterior cord. Innervates all the extensor muscles of the arm and forearm. Supplies elbow and wrist joints and the skin of the posterior arm, some of the posterior forearm, and some of the dorsal of the hand.

Thoracodorsal nerve

C6-C8. Innervates latissimus dorsi muscle

Medial cord

C8-T1. Continuation of the anterior division of the inferior trunk. Five nerves arise directly from the medial cord: medial pectoral nerve, medial brachial cutaneous nerve, medial antebrachial cutaneous nerve, ulnar nerve, medial root of the median nerve.

Ulnar nerve

C8-T1. Innervates 1&1/2 muscles of the flexor forearm and most of the intrinsic muscles of the hand. Supplies the elbow and wrist joints and skin on the medial palmar and dorsal surfaces of the hand. One of two terminal branches of the medial cord

Medial pectoral nerve

C8-T1. Innervates pectoralis minor and part of pectoralis major (sternocostal head).

Medial brachial cutaneous nerve

C8-T1. Provides cutaneous innervation to the medial side of the arm.

Medial antebrachial cutaneous nerve

C8-T1. Provides cutaneous innervation to the medial side of the forearm

Medial root of median nerve

C8-T1. The other terminal branch of the medial cord. Joined by the lateral root of the median nerve to form the median nerve

Winged scapula

Damage to the long thoracic nerve resulting in paralysis to serratus anterior. Medial border of scapula becomes unusually prominent.

Trunks

Divide into anterior and posterior divisions that reflect the embryology of the upper limb because anterior divisions supply preaxial muscles and posterior divisions supply postaxial muscles. Three trunks of the brachial plexus are located in the posterior triangle of the neck: superior (upper) trunk, middle trunk, and inferior (lower) trunk.

Rami

Form nerve structures called trunks. The ventral rami are the most proximal portion of the brachial plexus. Two nerves arise directly from the rami: Dorsal scapular nerve and long thoracic nerve.

Cords

Formed by anastomoses in anterior and posterior divisions. Three cords of the brachial plexus are located in the axilla. Each are named with respect to the part of the axillary artery deep to the pectoralis minor muscle. Each cord of the brachial plexus divides into two terminal branches.

Superior (upper) trunk

Formed by the rami of C5 and C6. Gives rise to suprascapular nerve and nerve to subclavius.

Inferior (lower) trunk

Formed by the rami of C8 and T1. Does not give rise to nerves.

Postganglionic sympathetic fibers

Join ventral rami via gray rami communicantes and distribute with the branches of the brachial plexus. There are no parasympathetic fibers in these branches to structures in the upper limb

Injuries to upper part of brachial plexus

Usually result from excessive separation of the neck and shoulder (motorcycle accident, person thrown and hits tree shoulder-first). Rami of spinal nerves C5-C6 may be pulled out of the spinal cord or the superior trunk may be torn. Err-Duchenne paralysis, causes upper limb to hang in a "waiter's tip" position.

Injuries to the lower part of the brachial plexus

Can result if upper limb is suddenly pulled superiorly (forceful pull during baby delivery). Involve injury to C8-T1 - most of the intrinsic hand muscles are paralyzed. Klumpke's paralysis - claw hand.

Middle Trunk

Continuation of C7 ramus. Does not give rise to nerves.

Cervical rib syndrome

Damage to the inferior trunk (C8-T1) by stretching an accessory rib