Ch.41 Brachial Plexus

Branches of the ventral rami

-Dorsal scapular nerve -Long thoracic nerve

Branches of the cords

-Lateral pectoral nerve -Medial pectoral nerve -Medial brachial cutaneous nerve -Medial antebrachial cutaneous nerve (MAC) -Upper subscapular nerve -Thoracodorsal nerve -Lower subscapular nerve -Axillary nerve

Definition of the brachial plexus

Network of intermingling and intertwining nerves that supplies structures of the upper limb plexus = twining or braid

Is the brachial plexus made of ventral rami or dorsal rami?

Spinal nerves are derive only from ventral rami and never from dorsal rami. The brachial plexus is formed directly from the ventral rami of spinal nerves C5-T1

Where are cords found?

The axilla

Where are trunks found?

The neck

Nerves derived from cords (primary nerves)

-Musculocutaneous nerve -Ulnar nerve -Radial nerve -Median nerve

Branches of the trunks

-Nerve to subclavius -Suprascapular nerve

Upper trunk

C5 and C6

Middle trunk

C7

Lower trunk

C8 and T1

Musculocutaneous nerve

Continuation of the lateral cord of the brachial plexus, beginning after the lateral root to the median nerve is given off

Ulnar nerve

Continuation of the medial cord of the brachial plexus, beginning after the medial root to the median nerve is given off

Radial nerve

Continuation of the posterior cord of the brachial plexus, beginning after the axillary nerve is given off

Median nerve

Derived from the lateral root of the median nerve and the medial root of the median nerve

Lateral pectoral nerve

Originates from the lateral cord; courses through the fascia above pectoralis minor into the deep surface of the pectoralis major muscle, which it supplies

Medial antebrachial cutaneous nerve

Originates from the medial cord; descends below the middle of the forearm, where it pierces the antebrachial fascia and supplies the skin on the medial forearm

Medial brachial cutaneous nerve

Originates from the medial cord; pierces the fascia of the proximal arm and supplies the skin on the lower medial arm

Medial pectoral nerve

Originates from the medial cord; pierces the pectoralis minor muscle and passes through to the deep surface of the pectoralis major, supplying both muscles

Thoracodorsal nerve

Originates from the posterior cord; courses inferiorly and posteriorly to the deep surface of the latissimus dorsi muscle, which it innervates

Axillary nerve

Originates from the posterior cord; courses inferiorly through the quadrangular space of the shoulder, passes medial to the surgical neck of the humerus, and innervates the teres minor and deltoid muscles

Upper subscapular nerve

Originates from the posterior cord; courses into and supplies the subscapularis muscle

Lower subscapular nerve

Originates from the posterior cord; courses over the anterior surface of the subscapularis muscle and divides into 2 muscular branches, one supplying the subscapularis muscle and the other supplying the trees major muscle

Suprascapular nerve

Originates from the upper trunk; coursing laterally and posteriorly, this nerve passes through the suprascapular notch and enters the supraspinous fossa, innervating the supraspinous muscle; then courses around the spine of the scapula and enters the infraspinous fossa, innervating the infraspinous muscle

Nerve to subclavius

Originates from the upper trunk; descends posterior to the clavicle, ending in and suppling the subclavius muscle

Long thoracic nerve

Originates from the ventral rami of C5, C6, and C7; courses posterior to the axillary artery and courses on the external surface of the serratus anterior muscles, which it supplies

Dorsal scapular nerve

Originates from the ventral ramus of C5; courses deep to levator scapula and enters the deep surface of the rhomboids, supplying rhomboid major and rhomboid minor muscles

What is the order of parts of the brachial plexus from proximal to distal?

Roots, trunks, divisions, cords, branches

What forms the posterior cord?

The 3 posterior divisions of the upper, middle, and lower trunks all join to form the posterior cord

What forms the medial cord?

The anterior division of the lower trunk continues as the medial cord

What forms the lateral cord?

The anterior divisions of the upper and middle trunks joint to form the lateral cord

How many nerves are given off by the cords?

The cords give off a total of 8 nerves and then continue distally as the four major nerves of the upper limb

Where do the cords get their names from?

The names of lateral, posterior, and medical indicate their location in relation to the axillary artery