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AXILLA BRACHIAL PLEXUS By: Dr. Musaed Al-Fayez Functions of the Nerves Entering The Upper Limb 1. Sensory innervation to the skin and joints 2. Motor innervation to the muscles 3. Influence over the diameter of blood vessels via sympathetic vasomotor nerves 4. Sympathetic secretomotor supply to the sweat glands What is a Brachial Plexus ? Brachial Plexus are complicated plexus of nerves present at the root of the neck to enter the upper limb This allows the nerve fibers derived from different segments of the spinal cord to be arranged and distributed efficiently in different nerve trunks to the various parts of the upper limb Location & Formation Brachial Plexus is present in the lower part of the posterior triangle of the neck & Axilla It is formed by the union of the anterior rami of the 5th, 6th, 7th and 8th cervical and the 1st thoracic spinal nerves Formation The Plexus can be divided into: • Roots • Trunks • Divisions • cords The roots of C5 & 6 unite to form upper trunk The root of C7 continues as the middle trunk The roots of C8 & T1 unite to form lower trunk Divisions Each trunk divides into anterior and Posterior divisions • • • The anterior divisions of the upper and middle trunks unite to form the lateral cord The anterior division of the lower trunk continues as the medial cord The posterior divisions of all three trunks join to form the posterior trunk Axillary Sheath The cords become arranged around the axillary artery in the axilla Brachial Plexus, the axillary artery and vein are enclosed by a sheath of fascia called AXILLARY SHEATH Relation of Cords All three cords of the brachial plexus lie above and lateral to the first part of axillary artery Relation of Cords Medial cord crosses behind the artery to reach the medial side of the second part of the axillary artery Posterior cord lies behind the second part of the artery Lateral cord lies on the lateral side of the second part of the artery Branches The branches of the different parts of the brachial plexus are: Roots: • Dorsal scapular nerve (C5) • Long thoracic nerve (C5, 6 and 7) Upper Trunk: • • Nerve to subclavius (C5 and 6) Suprascapular nerve (supplies the supraspinatus and infraspinatus muscles) Lateral Cord: • Lateral pectoral nerve • Musculocutaneous nerve • Lateral root of median nerve Medial Cord: • • Medial pectoral nerve Medial cutaneous nerve of arm and medial cutaneous nerve of forearm • Ulnar nerve • Medial root of median nerve Posterior Cord: • Upper and lower subscapular nerves • Thoracodorsal nerve • Axillary nerve • Radial nerve Branches in Axilla Nerve to Subclavius: Supplies the subclavian muscle May give contribution (C5) to the phrenic nerve Long Thoracic Nerve: Arises from the root Enters the axilla by passing down over the lateral border of the 1st rib behind the axillary vessels and brachial plexus Supplies the serratus anterior muscle Lateral Pectoral Nerve: Arises from the lateral cord Supplies the pectoralis major muscle Musculocutaneous Nerve: Arises from the lateral cord Supplies the coracobrachialis muscle Leaves the axilla by piercing this muscle Lateral Root of the Median Nerve: Is a direct continuation of the lateral cord Is joined by the medial root to form the median nerve trunk Gives no branch in the axilla Medial Pectoral Nerve: Arises from the medial cord Supplies and pierces the pectoralis minor Muscle Supplies the pectoralis major muscle Medial Cutaneous Nerve of the Arm Arises from the medial cord Is joined by intercostobrachial nerve Supplies the skin on the medial side of the arm Medial Cutaneous Nerve of the Forearm: Arises from the medial cord Descends in front of the axillary artery Ulnar Nerve: Arises from the medial cord Descends between axillary artery and vein Gives no branches in the axilla Medial Root of the Median Nerve: Arises from the medial cord Crosses in front of the 3rd part of axillary artery Joins the lateral root of the median nerve Upper and Lower Subscapular Nerve: Arise from the posterior cord Supply the upper and lower part of the suscapularis muscle and teres muscle (only lower subscapular nerve) Thoracodorsal Nerve: Arises from the posterior cord Runs downward to supply the latissimus dorsi muscle Axillary Nerve: Is one of the terminal branches of posterior cord Gives branch to the shoulder joint Divides into anterior and posterior branches Radial Nerve: Largest branch of brachial plexus Lies behind the axillary artery Supplies the long and medial heads of Triceps muscle and the posterior cutaneous nerve of the arm