Muscles of the Shoulder Joint

Muscles of the Shoulder Joint

• Teres major: origin from the lower 1/3 of the dorsum of the lateral border of the scapula, insertion into the medial lip of the bicipital groove, nerve supply from the lower subscapular nerve (C5,6), and action includes extension, adduction, and medial rotation of the arm.

Inter-muscular Spaces

• Quadrangular space: boundaries include superiorly - subscapularis, inferiorly - teres major, medially - long head of triceps, and laterally - shaft of the humerus; contents include axillary (circumflex) nerve and posterior circumflex humeral vessels.
• Upper triangular space: boundaries include superiorly - teres minor, inferiorly - teres major, and laterally - long head of triceps; contents include radial nerve and profunda brachii artery.
• Lower triangular space: boundaries include superiorly - teres major, inferiorly - teres major, and laterally - surgical neck of the humerus; contents include radial nerve and profunda brachii artery.

The Axilla

• Definition: a pyramidal space between the upper part of the chest and the upper part of the arm.
• Shape: apex, base, and 4 walls.
• Walls: anterior wall formed by pectoralis major, subclavius, and pectoralis minor; posterior wall formed by scapula overlaid by subscapularis, teres major, and latissimus dorsi.

Shoulder Girdle

• Bones forming it: clavicle and scapula.
• Joints: acromioclavicular and sternoclavicular.
• Ligaments: superior and inferior acromioclavicular, coracoclavicular, anterior and posterior sternoclavicular, costoclavicular, and interclavicular.

Movements of the Scapula

• Elevation: levator scapulae, upper trapezius, and serratus anterior.
• Depression: pectoralis minor, lower trapezius, and rhomboids.
• Protraction: serratus anterior and pectoralis minor.
• Retraction: rhomboids and middle trapezius.
• Upward rotation: upper trapezius, serratus anterior, and levator scapulae.
• Downward rotation: rhomboids, levator scapulae, and pectoralis minor.

Brachial Plexus

• Definition: formed by the anterior rami of the lower 4 cervical and the 1st thoracic nerves.
• Formation: 5 stages - roots, trunks, divisions, cords, and branches.
• Roots: ventral rami of the 5th, 6th, 7th, and 8th cervical and the 1st thoracic nerves.
• Trunks: 3 in the neck - upper, middle, and lower trunks.
• Divisions: 6 behind the clavicle - anterior and posterior divisions of each trunk.
• Cords: 3 in the axilla - lateral, medial, and posterior cords.
• Branches: dorsal scapular nerve, long thoracic nerve, nerve to subclavius, suprascapular nerve, lateral pectoral nerve, musculocutaneous nerve, lateral root of median nerve, medial pectoral nerve, medial cutaneous nerve of the forearm, medial cutaneous nerve of the arm, medial root of median nerve, ulnar nerve, upper subscapular nerve, lower subscapular nerve, thoracodorsal nerve, axillary nerve, and radial nerve.

Axillary Lymph Nodes

• Arranged in 5 groups.

This quiz covers the anatomy of the shoulder joint, including the teres major muscle, its origin, insertion, nerve supply, and action, as well as the intermuscular spaces.