Axilla Anatomy and Embryology PDF 2024/2025

MSK(101-1) Academic year: 2024/2025 Anatomy & Embryology Department Axilla Prof. Dr. Hayam Elsaady Farhoud  AXILLA Definition: It is a pyramidal space between the arm and the chest wall, or at the junction of the upper limb and the thorax. Importance o...

MSK(101-1) Academic year: 2024/2025 Anatomy & Embryology Department Axilla Prof. Dr. Hayam Elsaady Farhoud  AXILLA Definition: It is a pyramidal space between the arm and the chest wall, or at the junction of the upper limb and the thorax. Importance of the axilla: It is a way by which neurovascular and muscular structures can enter and leave the upper limb. Boundaries of the axilla: It has 4 walls (anterior, posterior, medial and lateral),an apex directed upwards, and a base directed downwards.  BOUNDARIES OF THE AXILLA Anterior Wall: Superficial layer : pectoralis major muscle. Deep layer: (from above downwards) -subclavius muscle, -clavipectoral fascia, -pectoralis minor and -suspensory ligament of the axilla Posterior Wall: Subscapularis, Teres major Latissimus dorsi. N.B: -The lower margin of the anterior wall is called the anterior fold. -It is formed by the pectoralis major only. -The lower margin of the posterior wall is called the posterior fold. - It is formed by the teres major and latissimus dorsi. The posterior fold extends downwards more than the anterior fold. Medial Wall: -Upper 5 ribs and related intercostal spaces -upper digitations of the serratus anterior which arise from the upper 5 ribs. Lateral Wall: Upper part of the shaft of the humerus (Bicipital groove of the humerus) Coracobrachialis muscle and short head of biceps (where it joins the coracobrachialis) N.B: - the lateral wall of the axilla is narrow as compared with the medial wall. Thus, the anterior and posterior walls converge on the lateral wall. Base: Is formed by thickened deep fascia, called axillary fascia and skin. This fascia forms the floor of the axilla and connect the anterior and posterior walls. It extends from the pectoralis major in front to the latissimus dorsi behind. Boundaries of Base : 1. Anteriorly: The anterior axillary fold which formed by the lower border of pectoralis major muscle. 2. Posteriorly: The posterior axillary fold which formed by the tendons of latissimus dorsi and teres major muscles. It becomes tense when the arm is abducted or raised above the head. Apex: (Cervicoaxillary canal) -Is directed upwards and communicates with the neck through a triangular gap. -This gap transmits the axillary vessels and the cords of the brachial plexus from the neck to the arm. - Boundaries of the apex : Anteriorly: the clavicle. Posteriorly: upper border of the scapula. Medially: outer border of the 1st rib. CONTENTS OF THE AXILLA -Axillary artery and its branches. -Axillary vein and its tributaries. They cross the axilla from medial to lateral, ( the vein medial to the artery all through). -Cords of the brachial plexus and their branches. -the lateral, medial and posterior cords, surround the 1st and 2nd parts of the axillary artery. - their branches around the 3rd part of the axillary artery -Long thoracic nerve (nerve to serratus anterior) Intercostobrachial nerve. -Lateral cutaneous branches of the 3rd to the 6th intercostal nerves. -Terminal part of cephalic vein. -Axillary lymph nodes: arranged in groups , Contents of the axilla  AXILLARY ARTERY It begins at the outer border of the 1st rib as the continuation of the subclavian artery. It ends at the lower border of teres major where it becomes the brachial artery. Course: It descends downwards and laterally through the axilla from its apex (at the outer border of the 1st rib) to reach its base (at the lower border of the teres major muscle) to continue in the arm as brachial artery. The axillary artery is divided into 3 parts by the pectoralis minor The axillary artery is divided into 3 parts by the pectoralis minor which crosses over it: 1.1st part: above the level of the pectoralis minor. 2.2nd part: under cover of the pectoralis minor. 3.3rd part: below or distal to the pectoralis minor. Lateral Medial Lateral Medial Posterior A) RELATIONS OF 1st PART: Anteriorly: 1.Skin, superficial fascia (containing platysma muscle and supraclavicular nerves) and deep fascia. 2. Clavicular head of Pectoralis major muscle. 3. Subclavius muscle 4. Clavipectoral fascia 5. Cephalic vein Lateral Medial 1.1st part Posterior Posteriorly: 1-1st digitation of serratus anterior. 2- Nerve to serratus anterior 3-Medial cord of brachial plexus, separating the artery from the serratus anterior. Medially:- Axillary vein, ♦ Above and lateral: -The lateral cord (above) -The posterior cord (lateral). Branches:- Superior thoracic artery.  Lateral Medial Posterior RELATIONS OF 2nd PART: lies behind the pectoralis minor muscle. Anterior: -Skin, superficial fascia and deep fascia. -Pectoralis major muscle. -Clavipectoral fascia. -Pectoralis minor muscle. Lateral Medial 2nd part Posterior Posterior:-posterior cord, separating the artery from the subscapularis muscle.. Medial: The medial cord, separating the artery from the axillary vein. Medial pectoral nerve. Lateral: The lateral cord, separating the artery from the coracobrachialis. The arrangement of the 3 cords around the 2nd part of the artery according to their names, i.e. the lateral cord is lateral, the medial cord is medial and the posterior cord is posterior to the artery.  Lateral Medial Posterior RELATIONS OF 3rd PART: - It extends from the lower border of pectoralis minor to the lower border of teres major muscle. It is superficial and its lower 1/2 can be felt pulsating under the skin. It is surrounded by the branches of the 3 cords. Anterior: Upper 1/2: Skin, superficial fascia,  Lateral Medial 3rd PART Posterior Posterior: -Axillary nerve: separating the artery from the subscapularis. -Radial nerve: separating the artery from the insertions of latissimus dorsi and teres major. Medial: -Axillary vein, -ulnar nerve -Medial cutaneous nerve of the arm (separating OF BRANCHES the 3rd artery from(3 PART: the axillary vein). branches). -Medial cutaneous nerve of the forearm. -Subscapular artery Lateral:. Coracobrachialis muscle. -Posterior circumflex humeral. Lateral root of median nerve  3rd 2nd 1st