Brachial Plexus PDF

Axilla BRACHIAL PLEXUS - Formation (Stages) (Figs. 55, 56): it is a collection of nerves, which lie partly in the neck and partly in the axilla. It consists of roots, trunks, divisions and cords. A. Roots: is formed by the ventral (anterior) primary rami of th...

Axilla BRACHIAL PLEXUS - Formation (Stages) (Figs. 55, 56): it is a collection of nerves, which lie partly in the neck and partly in the axilla. It consists of roots, trunks, divisions and cords. A. Roots: is formed by the ventral (anterior) primary rami of the 5, 6, 7 and 8 cervical and 1st thoracic nerves. 25 6 7 Tr.. B. Trunks: 1. Upper trunk is formed by union of 5th and 6th cervical roots. 2. Middle trunk is formed by ih cervical root only. 3. Lower trunk is formed by union of sth cervical and 1st thoracic roots. The three trunks lie above the clavicle, in the neck C. Divisions: each trunk divides, behind the clavicle, into anterior (ventral) and posterior (dorsal) divisions, D. Cords: the plexus consists of three cords which lie in the axilla. 1. Medial cord is formed by the anterior division of the lower trunk. 2. Lateral cord is formed by fusion of the anterior divisions of the upper and middle trunks. 3. Posterior cord is formed by fusion of the posterior divisions of the three trunks. N.B. All branches of both lateral and medial cords supply the flexor side/ while all branches of the posterior cord supply the extensor side of the upper limb. - Site (Fig. 56): A. Roots and trunks lie in the neck: the roots lie in the neck B. Divisions: lie in the apex of axilla behind the clavicle. C. Cords and its branches: lie in the axilla Branches of the brachial plexus (Fig. 55): arise from the roots, the upper trunk and the three cords. A- Branches of the Roots: 1. Nerve to rhomboids (dorsal scapular Nerve): Arises from the root of C5. Descends along medial border of scapula deep to levator scapulae and rhomboid muscles and supplies them 2. Nerve to serratus anterior (long thoracic Nerve): It arises from the roots of C5, 6 and 7. It descends vertically, in the midaxillary line, on the outer surface of serratus anterior muscle supplying it.  Axilla B- Branches of the Trunks (only from the upper trunk): 1. Nerve to Subclavius (CS and 6): It arises from the upper trunk and descends in front of the brachial plexus to reach the subclavius muscle. 2. Suprascapular Nerve (CS and 6): It arises from the upper trunk and runs downwards and laterally in neck to reach the suprascapular notch. It passes through the supra-scapular foramen (below the supra- scapular ligament) to reach the supra-spinous fossa where it runs deep to supraspinatus muscle and supplies it. Then it descends through the spino-glenoid notch to reach the infra- spinous fossa where it ends by supplying infra-spinatus muscle. It gives also articular branches to supply the acromioclavicular and shoulder joints. Cords Divisions ', Trun k s '1 Roots C5 · Dorsoal scapul;ar nerw - - \_ _ __ l \ '\ \ Suprascapular nerVI!! \ C6 Nerve to subcl.avius - -- ,- , \ C7 lAteral pectoral nerv C8 Tl AJoillary nerw Upper subscapular ner"" Thoraco dorsal nerve Lower subscapul.;or ne""" Uln.;or nerve Medial cutaneous nerW! ofthe arm Medial cutaneous ner'IM ofthe forearm Fig. 55: Formation and branches of brachial plexus  Axilla C- Branches of the Cords (Fig. 56): : Branches of Lateral Cord: 25 6 7 , , 1. Musculocutaneous nerve (CS, 6 & 7): is the largest branch. 2. Lateral root of median nerve (CS, 6 &7) 3. Lateral pectoral nerve {CS, 6 and 7): is larger than the medial pectoral nerve. It pierces clavi-pectoral fascia and ends by supplying the pectoralis major muscle. : Branches of Medial Cord: 18 51 außer 1 , 1. Ulnar nerve (C7, 8 and Tl): is the largest branch. 2. Medial root of median nerve (C8 and Tl). 3. Medial pectoral nerve (C8 and Tl): it pierces and supplies pectoralis minor and ends by supplying pectoralis major. 4. Medial cutaneous nerve of the arm (C8 and Tl): supplies the skin on the medial side of the lower half of the arm. 5. Medial cutaneous nerve of the forearm (C8 and Tl): Descends medial to the third part of axillary artery and upper half of the brachial artery. Supplies the skin of the medial side of the forearm to the wrist. Lateral Medial Posterior \ \ \ \ \ \ \ \.. \ \ Axillary nerve (posterior cord) \ \ \ Musculocutaneous nerve (lateral cord) \ \ \ Radial nerve (posterior cord) \ ' Mooian nerve (medial and lateral cords) \ Ulnar nerve (medial cord) Fig. 56: Formation of brachial plexus & location (Anterior view)  Axilla ! Branches of the Posterior Cord (Fig. 57): 1. Radial nerve (C5, 6, 7, 8 and Tl): is the larger of the two terminal branches of the posterior cord (will be discussed later). 2. Axillary {circumflex) nerve (C5, 6) (Figs. 57, 58): - Origin: is the smaller of the two terminal branches of the cord. -Course: It passes downwards and laterally on the subscapularis muscle behind the third part of axillary artery. On reaching the lower border of subscapularis, it passes backwards through the quadrangular space (accompanied by posterior circumflex humeral artery) where they lie below the capsule of the shoulder joint. It turns around the back of the surgical neck of the humerus where it gives an articular branch to the shoulder joint. - It ends by dividing into: Anterior branch: it continues its course round the surgical neck to end near the anterior border of deltoid muscle, supplying it. Posterior branch: it gives a branch to the teres minor and then curves around the posterior border of deltoid to become the upper lateral cutaneous nerve of the arm which supplies the skin over the lower half of the deltoid. 3. Upper subscapular nerve (C5 and 6): supplies the upper part of the subscapularis muscle. 4. Lower subscapular nerve (C 5 and 6): supplies the lower part of subscapularis muscle and teres major muscle. 5. Nerve to Latissimus Dorsi (Thoraco-dorsal nerve): (C6, 7 & 8) It arises from the posterior cord. It supplies the latissimus dorsi muscle.