THE AXILLA OF THE UPPER LIMB AND ITS CONTENTS

gross anatomy of the axilla

1. THE AXILLA INTRODUCTION BORDERS CONTENTS CLINICAL RELEVANCE

2. Commonly known as the armpit or underarm Pyramidal space between the shoulder girdle and the thoracic wall Lies underneath the glenohumeral joint and superior to the axillary fascia at the junction of the arm and thorax Passageway by which neurovascular structures enters and leaves the upper limb. S hape and size of the axilla varies, depending on the position of the arm; it flattens when the arm is fully abducted INTRODUCTION

3. BORDERS OF THE AXILLA The borders or boundaries of the axilla are: Inlet known as the Apex Four (4) sides known as the walls: Anterior, Medial Lateral and Posterior Floor known as the Base N.B. The axillary inlet is continuous superiorly with the neck and the lateral part of the floor opens into the arm.

4. BORDERS OF THE AXILLA Apex: cervico -axillary canal passageway between the neck and axilla bounded by the 1st rib, clavicle, and superior border of the scapula arteries , veins, lymphatics , and nerves traverse the apex to pass to or from the arm

5. BORDERS OF THE AXILLA BASE: bounded by the skin of armpit (concave skin), sub- cuteneous tissue and axillary (deep) fascia spanning from the arm to the thoracic wall (approximately the 4th rib level) forming the axillary fossa (armpit ). N.B: The base of the axilla and axillary fossa are bounded by the anterior and posterior axillary folds , the thoracic wall, and the medial aspect of the arm

6. BORDERS OF THE AXILLA ANTERIOR WALL: has two layers which are formed by the pectoralis major and pectoralis minor with the pectoral and clavicopectoral fascia associated with them . The anterior axillary fold is the inferiormost part of the anterior wall that may be grasped between the fingers . It is formed by the pectoralis major, as it bridges from thoracic wall to humerus , and the overlying integument

7. BORDERS OF THE AXILLA POSTERIOR WALL: on its anterior surface, it is formed by the scapula and subscapularis inferiorly by the teres major and latissimus dorsi . The posterior axillary fold is the inferiormost part of the posterior wall that may be grasped. It extends farther inferiorly than the anterior wall and is formed by latissimus dorsi , teres major, and overlying integument.

8. BORDERS OF THE AXILLA MEDIAL WALL: f ormed by the thoracic wall (1st–4th ribs), intercostal muscles and the overlying serratus anterior muscle LATERAL WALL: is a narrow bony wall formed by the intertubercular sulcus/groove of the humerus

9. BORDERS OF THE AXILLA

10. CONTENTS OF THE AXILLA Axillary arteries and its branches Axillary veins and its tributaries Lymphatic vessels and groups of axillary lymph nodes Large nerves that make up the chords and branches of the brachial plexus N.B: Proximally, these structures are ensheathed in the axillary sheath (a sleeve-like extension). The first 3 contents are embedded in a matrix of axillary fat

11. CONTENTS OF THE AXILLA Axillary artery (and branches)  – the main artery supplying the upper limb. It is commonly referred as having three parts; one medial to the pectoralis minor, one posterior to pectoralis minor, and one lateral to pectoralis minor. The medial and posterior parts travel in the axilla.

12. CONTENTS OF THE AXILLA Axillary vein- is a large vein formed by the union of the brachial vein and basilic vein at the inferior border of teres major. Brachial plexus (and branches) – a major nerve collections that supplies the upper limb. Axillary lymph nodes  – they filter lymphatic fluid that has drained from the upper limb and pectoral region.

13. CLINICAL RELEVANCE Aneurysm of Axillary Artery: This is when the first part of the axillary artery enlarges and compresses the trunks of the brachial plexus, causing pain and anesthesia (loss of sensation) in the areas of the skin supplied by the affected nerves. It may occur in baseball pitchers because of their rapid and forceful arm movements . Lymphadenopathy: is a palpable enlargment of the lymph nodes i.e. the lymph nodes becomes swollen ( abnormal in size). Surgical Importance : the axillary region is commonly exposed during breast cancer surgeries to remove lymph nodes and also in brachial plexus blocks.

14. CLINICAL RELEVANCE