The Axilla

Contents of the Axilla: The axillary artery and its branches, which supply blood to the upper limb. The axillary vein and its tributaries, which drain blood from the upper limb. The lymph vessels and lymph nodes, which drain lymph from the upper limb and the breast and from the skin of the trunk, down as far as the level of the umbilicus. The brachial plexus, is an important nerve plexus, which innervates the upper limb.

The axillary lymph nodes Lymph Nodes of the Axilla The axillary lymph nodes The axillary lymph nodes (20 to 30 in number) embedded in connective tissue and fat. They drain lymph vessels from the lateral quadrants of the breast, the superficial lymph vessels from the thoracoabdominal walls above the level of the umbilicus, and the vessels from the upper limb.

The axillary lymph nodes The lymph nodes are arranged in six groups.

The axillary lymph nodes ■ Anterior (pectoral) group: Lying along the lower border of the pectoralis minor behind the pectoralis major.

Lymph Nodes of the Axilla ■ Posterior (subscapular) group: Lying in front of the subscapularis muscle.

Lymph Nodes of the Axilla ■ Lateral group: Lying along the medial side of the axillary vein, these nodes receive most of the lymph vessels of the upper limb.

Lymph Nodes of the Axilla ■ Central group: Lying in the center of the axilla in the axillary fat, these nodes receive lymph from the above three groups.

Lymph Nodes of the Axilla ■ Infraclavicular (deltopectoral) group: they are located outside the axilla. They lie in the groove between the deltoid and pectoralis major muscles.

Lymph Nodes of the Axilla ■ Apical group: Lying at the apex of the axilla at the lateral border of the 1st rib, these nodes receive the efferent lymph vessels from all the other axillary nodes. The apical nodes drain into the subclavian lymph trunk.

Contents of the Axilla Brachial Plexus

Brachial Plexus The nerves entering the upper limb at the root of the neck, and form a complicated plexus called the Brachial plexus. This allows the nerve fibers derived from different segments of the spinal cord to be arranged and distributed in different nerve trunks to the various parts of the upper limb.

Brachial Plexus The brachial plexus is formed in the posterior triangle of the neck by the union of the anterior rami of the 5th, 6th, 7th, and 8th cervical and the 1st thoracic spinal nerves.

Brachial Plexus The brachial plexus is divided into roots, trunks, divisions, and cords. The roots of C5 and 6 unite to form the upper trunk, the root of C7 continues as the middle trunk, and the roots of C8 and T1 unite to form the lower trunk.

Brachial Plexus Each trunk then 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, and the posterior divisions of all three trunks join to form the posterior cord.

Brachial Plexus The roots, trunks, and divisions of the brachial plexus reside in the lower part of the posterior triangle of the neck. The cords become arranged around the axillary artery in the axilla. Here, the brachial plexus and the axillary artery and vein are enclosed in the axillary sheath.

Brachial Plexus Cords of the Brachial Plexus: All three cords of the brachial plexus lie above and lateral to the first part of the axillary artery. The medial cord crosses behind the artery to reach the medial side of the second part of the artery. The posterior cord lies behind the second part of the artery, and the lateral cord lies on the lateral side of the second part of the artery.

Brachial Plexus Cords of the Brachial Plexus: All the cords of the plexus have the relationship to the second part of the axillary artery that is indicated by their names. Most branches of the cords that form the main nerve trunks of the upper limb continue this relationship to the artery in its third part.

Brachial Plexus The branches of the different parts of the brachial plexus: Roots: 1. Dorsal scapular nerve (C5) 2. Long thoracic nerve (C5, 6, and 7) Upper trunk: Nerve to subclavius (C5 and 6) 2. Suprascapular nerve (supplies the supraspinatus and infraspinatus muscles)

Brachial Plexus The branches of the different parts of the brachial plexus: Lateral cord: 1. Lateral pectoral nerve 2. Musculocutaneous nerve 3. Lateral root of median nerve Medial cord: 1. Medial pectoral nerve 2. Medial cutaneous nerve of arm. 3. Medial Cutaneous nerve of forearm 4. Ulnar nerve 5. Medial root of median nerve

Brachial Plexus The branches of the different parts of the brachial plexus: Posterior cord: 1. Upper and lower subscapular nerves 2. Thoracodorsal nerve 3. Axillary nerve 4. Radial nerve

Brachial Plexus Injuries

Brachial Plexus Injuries The roots, trunks, and divisions of the brachial plexus present in posterior triangle of the neck, whereas the cords and most of the branches of the plexus lie in the axilla. Complete lesions involving all the roots of the plexus are rare. Incomplete injuries are common and are usually caused by traction or pressure. It may occurs in infants during a difficult delivery. Individual nerves can be divided by stab wounds.

Brachial Plexus Injuries 1. Upper Brachial Plexus injury (C5 and C6 roots): this lead to loss of functions of all nerves arise from these roots as axillary nerve, musculocutaneous nerve, etc and this will lead to paralysis of the muscles supplied by these affected nerves as supraspinatous, infraspinatous, deltoid, biceps brachii muscles, etc. This will lead to deformity of the upper limb called waiter tip deformity. In addition there will be loss of sensation down the lateral side of the arm. Erb–Duchenne palsy (waiter’s tip)

Brachial Plexus Injuries 2. Lower Brachial Plexus injury (C7, C8, and T1 roots): this will affects the ulnar and median nerve fibers that supply all the small muscles of the hand. This will to a hand deformity called Claw hand. In addition, there will be loss of sensation along the medial side of the arm. Lower Brachial Plexus injury (Klumpke Palsy)