Anatomy: Shoulder and Axilla

• The lecture covers the shoulder and the axilla.

Objectives

• Explain the skeletal framework of the shoulder joint
• Describes the axilla's boundaries and contents
• Lists the scapula's landmarks and attached muscles
• Describes how the scapula moves via attached muscles
• Recognizes the pectoral muscles' function, supply, and innervation
• Names humerus-inserting scapula muscles that move the shoulder
• Describes brachial plexus formation and the major branches from the 3 cords
• Describes the branches from the trunks and divisions that innervate shoulder muscles and their functions
• Delineates the extent, distribution areas, and branches of the axillary artery
• Describes lymphatic drainage of the posterior shoulder, chest, and upper limb, including final destination

Shoulder

• The bones that form the shoulder joint include the scapula, clavicle, and humerus

Movements at Shoulder

• Flexion
• Extension
• Abduction
• Adduction
• Internal/medial rotation
• External/lateral rotation
• Protraction
• Retraction

Parts of the Scapula

• Glenoid labrum

• Glenoid cavity

• Head of humerus

• Tendon of long head of biceps brachii muscle

• Transverse humeral ligament

• Key landmarks to identify include the Coracoid process, Spine of scapula, Acromion, Supraspinous/Infraspinous/Subscapular Fossas, Suprascapular notch, Greater scapular notch, Glenoid cavity, Supra & infra glenoid tubercles and Angles & borders

The Upper and Mid Humerus

• Head of the humerus
• Greater tubercle
• Lesser tubercle
• Intertubercular sulcus
• Anatomical neck
• Surgical neck

Mid Humerus

• Deltoid tuberosity of humerus
• The spiral groove of the mid humerus

Movements Associated with Muscles Attached to the Scapula

• Elevation of shoulder is brought about by the trapezius and levator scapulae
• Depression of shoulder is brought about by the lower fibers of trapezius
• Retraction of shoulder is brought about by the rhomboid minor and major
• Protraction of shoulder is brought about by the serratus anterior
• Lateral rotation of the arm is brought about by the infraspinatus and teres minor
• Medial rotation of the arm is brought about by the subscapularis
• Adduction and medial rotation is brought about by the teres major
• Initiation of abduction – 15 degrees- supraspinatus
• Abduction- 15-90 degrees – deltoid
• Biceps (long head) causes flexion of the forearm
• Coracobrachialis causes adduction & flexion of arm
• Triceps (long head) extends and adducts the arm, also extends the forearm

Axilla

• The axilla is outlined with a series of boundaries
• The anterior wall consists of the Pectoralis major and minor muscles, Subclavius muscle and the Clavipectoral fascia
• The lateral wall consists of the Intertubercular sulcus
• The posterior wall consists of Subscapularis, teres major, latissimus dorsi and long head of triceps brachii muscles
• Contents include the anterior wall, lateral wall, and posterior wall

Axillary Artery and the Branches

• The axillary artery has been broken down into 3 parts and some branches that include the:
• Lateral margin of rib 1
• Subclavius
• Subclavian artery
• Superior thoracic artery
• Pectoralis minor Subclavius
• Thoracoacromial artery
• Subscapularis
• Subscapular artery
• Posterior circumflex humeral artery
• Lower border of teres major
• Brachial artery
• Anterior circumflex humeral artery
• Latissimus dorsi
• Circumflex scapular branch
• Lateral thoracic artery
• Profunda brachii artery

Innervation & Vascular Supply

• Nerves associated with the shoulder area include the spinal accessory that innervates the trapezius, the suprascapular which innervates the supraspinatus & infraspinatus
• Dorsal scapular innervates the levator scapulae, rhomboid major and minor. The axillary nerve innervates deltoid & teres minor
• The lower scapular nerve innervates subscapularis and teres major and long thoracic nerve which innervates serratus anterior
• Arteries that contribute to scapular anastomosis include Dorsal scapular, Suprascapular, Branches of axillary artery and Branches of thyrocervical trunk

Brachial Plexus and the main supply to shoulder

• The flexor compartment of the arm musculocutaneous, forearm which is the median nerve
• Extensor compartment arm-radial nerve, forearm is the radial nerve again
• Shoulder Suprascapular,Subscapular (upper & lower) and Axillary
• Other areas Thoracodorsal, Phrenic and Long thoracic

Lymphatic Drainage

• Groups of Lymph Nodes
• Subscapular (posterior): drains posterior shoulder region
• Humeral (lateral): drains the upper limb
• Pectoral (anterior): drain anterior chest/breast region
• Central nodes: posterior, lateral and anterior drains into central
• Apical nodes: central drains into apical group
• Right or left subclavian trunk