Axilla & Brachial Plexus PDF

Axilla & Brachial Plexus Dr. Shaima Abdelrahman Tagelsir MBBS U of K MSC Clinical Anatomy NUSU MRCS A Royal college of Edinburgh Intended learning outcome: At the end of this session, students will be able to: Outline general orientation & boundaries of the axilla Demonstrate its content Illustr...

Axilla & Brachial Plexus Dr. Shaima Abdelrahman Tagelsir MBBS U of K MSC Clinical Anatomy NUSU MRCS A Royal college of Edinburgh Intended learning outcome: At the end of this session, students will be able to: Outline general orientation & boundaries of the axilla Demonstrate its content Illustrate the major branches of the brachial plexus The Axilla: Or armpit, is a pyramid-shaped space between the upper part of the arm and the side of the chest.  It forms an important passage for nerves, blood, and lymph vessels as they travel from the root of the neck to the upper limb. Boundaries: apex, base & 4 walls: The upper end of the axilla, or apex, is directed into the root of the neck and is bounded in front by the clavicle, behind by the upper border of the scapula, and medially by the outer border of the first rib. The lower end, or base, is bounded in front by the anterior axillary fold (formed by the lower border of the pectoralis major muscle), behind by the posterior axillary fold (formed by the tendon of latissimus dorsi and the teres major muscle), and medially by the chest wall. The walls of the axilla are made up as follows: Anterior wall: By the pectoralis major, subclavius, and pectoralis minor muscles. Posterior wall: By the subscapularis, latissimus dorsi, and teres major muscles from above down Medial wall: By the upper four or five ribs and the intercostal spaces covered by the serratus anterior muscle Lateral wall: By the coracobrachialis and biceps muscles in the bicipital groove of the humerus The base is formed by the skin stretching between the anterior and posterior walls The clavipectoral fascia is a strong sheet of connective tissue that is attached above to the clavicle. Below, it splits to enclose the pectoralis minor muscle and then continues downward as the suspensory ligament of the axilla and joins the fascial floor of the armpit. Contents of the axilla: 1) The Axillary artery 2) The Axillary vein 3) The axillary lymph nodes 4) Brachial plexus 5) fats The axillary artery Begins at the lateral border of the 1st rib as a continuation of The subclavian and ends at the lower border of the teres major muscle, where it continues as the brachial artery. Throughout its course, the artery is closely related to the cords of the brachial plexus and their branches and is enclosed with them in a connective tissue sheath called the axillary sheath The pectoralis minor muscle crosses in front of the axillary artery and divides it into three parts First Bart: This extends from the lateral border of the 1st rib to the upper border of the pectoralis minor, its braches: 1. The highest thoracic artery Second part: This lies behind the pectoralis minor muscle, its branches: 1. The thoracoacromial artery 2. The lateral thoracic artery Third part: This extends from the lower border of the pectoralis minor to the lower border of the teres major, its branches: 1. The subscapular artery runs along the lower border of the subscapularis muscle. 2. The anterior and posterior circumflex humeral arteries wind around the front and the back of the surgical neck of the humerus, respectively The axillary vein: Is formed at the lower border of the teres major muscle by the union of the venae comitantes of the brachial artery and the basilic vein It runs upward on the medial side of the axillary artery and ends at the lateral border of the 1st rib by becoming the subclavian vein Receives tributaries, which correspond to the branches of the axillary artery, and the cephalic vein The axillary lymph nodes: The axillary lymph nodes (20 to 30 in number) 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 lymph nodes are arranged in six groups : All end in apical groups then drain into the subclavian lymph trunk. Groups Position Drained areas Anterior Lower border of Lateral quadrants of the breast and superficial vessels [pectoral] the pectoralis from the anterolateral abdominal wall above the level minor of the umbilicus Posterior In front of the The back, down as far as the level of the iliac crests. [subscapular] subscapularis muscle Lateral Medial side of the The upper limb (except those drained by infraclavicular axillary vein groups) Central Center of the axilla Above three groups. in the axillary fat Infraclavicular Groove between Lateral side of the hand, forearm, and arm. ** the deltoid and [deltopectoral pectoralis major ] muscles Apical Apex of the axilla All the other axillary nodes. at the lateral border of the 1st rib 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. Function: 1. Sensory innervation to the skin and deep structures, such as the joints 2. Motor innervation to the muscles; 3. Influence over the diameters of the blood vesselsby the sympathetic vasomotor nerves; and sympathetic secretomotor supply to the sweat glands. The plexus can be divided into roots, trunks, divisions, and cords Clinical notes: Erb’s palsy: upper root injery C5-6 [waiter’s tip deformity] Klumpke: lower root injery T1 [claw hand deformity] Quiz Which nerve has been highlited with green: The sum of anterior devisions of the superior and middle trunks give rise to: A. Medial cord B. Lateral cord C. Posterior cord D. Median nerve Which of the following nerves is branch of posterior cord: A. Muscolucutanious nerve B. Median nerve C. Axillary nerve D. Ulnar nerve References: Snell anatomy by regions 9th edition. Clinical oriented anatomy by K.moore Teach me anatomy website Netter atlas of anatomy