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 Muscles of the Superficial Layer Muscles of the Deep Layer Trapezius Levator scapulae Rhomboideus minor Rhomboideus major Latissimus dorsi There are 5 muscles that...

 Muscles of the Superficial Layer Muscles of the Deep Layer Trapezius Levator scapulae Rhomboideus minor Rhomboideus major Latissimus dorsi There are 5 muscles that connect the upper limb to the vertebral column. They are arranged in 2 layers; superficial and deep.  It is a large triangular muscle covering the upper ½ of the back.  The right and left muscles together form the outline of a trapezium. Origin of Trapezius The muscle has a wide origin from: 1) Back of the skull 2) Back of the neck 3) Back of the thorax Origin of Trapezius from Back of the Skull It arises from the external occipital protuberance and the medial 1/3 of the superior nuchal line External occipital protuberance Medial 1/3 of superior nuchal line Origin of Trapezius from Back of the Skull  Origin of Trapezius from Back of the Neck It arises from the ligamentum nuchae and the spine of the 7th cervical vertebra Ligamentum nuchae Spine of 7th cervical vertebra Ligamentum nuchae Spine of 7th cervical vertebra Origin of Trapezius from Back of the Thorax It arises from the spines of all thoracic vertebrae and their supraspinous ligaments Spines of all thoracic vertebrae and Their supraspinous ligaments  The upper fibers run downwards and Insertion of Trapezius laterally to insert into the posterior border of the lateral 1/3 of the clavicle The middle fibers run horizontally to insert into the medial border of the acromion process and upper lip of crest of spine of scapula The lower fibers run upwards and laterally to insert into the rough tubercle on the crest of the spine of scapula near the root of the spine  The upper fibers run downwards and laterally to insert into the posterior border of the lateral 1/3 of the clavicle V-shaped insertion embraced by the V- shaped origin of deltoid Trapezius M. Deltoid M.  Nerve Supply of Trapezius Motor; spinal root of accessory nerve Sensory; proprioceptive fibers from C3 and C4 Spinal root of accessory nerve  Spinal root of accessory nerve Vagus nerve Cranial root of accessory nerve Spinal root of accessory nerve  Action of Trapezius Remember: 1 The upper fibers pull the lateral 1/3 of the clavicle upwards towards the back of the skull 2 The middle fibers pull the acromion process and spine of scapula backwards towards the vertebral column 3 The lower fibers pull the medial part of the spine of scapula downwards towards the lower thoracic spines  Acting with the other muscles inserted into the scapula, it acts as a fixator that maintains the level of the shoulder during movements of the arm. If trapezius and other shoulder muscles are fatigued, they let the shoulder to drop.  The upper fibers elevate the shoulder girdle (shrugging of shoulder) [N.B.] These fibers have agonistic action with levator scapulae muscle  The middle fibers retract the scapula and brace back the shoulder [N.B.] These fibers have agonistic action with rhomboideus muscles  The upper and lower fibers acting together rotate the scapula so that glenoid cavity looks upwards, helping in raising arm above the head in abduction from 90-180° [N.B.] These fibers have agonistic action with the lower digitations of serratus anterior Applied Anatomy Paralysis of trapezius leads to shoulder drop Latissimus Dorsi M.  It is a broad flat triangular muscle that covers It has a very wide origin and a narrow insertion, the lower part of the back, extending from the and is the only back muscle that inserts into the iliac crest to the inferior angle of the scapula. arm (the others insert into shoulder girdle) Origin of latissimus dorsi Fleshy origin: 3) Dorsal aspect of inferior angle of scapula Tendinous (aponeurotic) origin: 1) Spines of lower 6 thoracic vertebrae (under cover of trapezius) 2) Outer surfaces of the lower 4 ribs 2) Thoracolumbar fascia (attaches the muscle to lumbar and sacral spines) 1) Posterior 1/3 of outer lip of iliac crest  Origin of latissimus dorsi muscle from the outer surfaces of the lower 4 ribs Origin of latissimus dorsi muscle from the thoraco- lumbar fascia  Latissimus dorsi M. External abdominal oblique M.  Insertion of latissimus dorsi Finally the muscle inserts 3 into the floor of the bicipital groove of the humerus Upper border of the muscle crosses over the Then the muscle forms a inferior angle of the trible relation with teres scapula major muscle; first behind it, then below it and finally in front of it 1 2 Nerve supply of latissimus dorsi Thoracodorsal nerve (nerve to latissimus dorsi) This nerve arises from the posterior cord of the brachial plexus  Action of latissimus dorsi 1) Adduction, extension and medial rotation of arm as in swimming and rowing 2) Acting from its insertion, it pulls the trunk upwards as in climbing and chin up training (this action is agonistic with sternocostal head of pectoralis major muscle) 3) It assists in violent expiration as in coughing and sneezing by compression of the lower ribs Triangles related to latissimus dorsi  Triangle of Auscultation Location; medial to lower part of scapula Boundaries; Medially; lateral border of Triangle of trapezius auscultation Laterally; medial border of scapula 6th rib Below; upper border of 7th rib latissimus dorsi Floor; rhomboideus major muscle, 6th and 7th ribs Rhomboideus and the space between major muscle them Importance; breath sounds are clearly heard (auscultated) over this triangle  Lumbar triangle of Petit Location; above the junction of the posterior 1/3 and anterior 2/3 of iliac crest Boundaries; Laterally; posterior border of external abdominal oblique muscle Medially; lateral border of latissimus dorsi muscle Below; iliac crest Lumbar hernia Floor; internal abdominal of Petit oblique and transversus abdominis muscles Importance; it might be the site of a hernia (lumbar hernia) Lumbar triangle of Petit Origin; from transverse processes of the upper 4 cervical vertebrae Levator Scapulae M. Insertion; into dorsal surface of medial border of scapula, from the superior angle to the root of the spine Nerve supply; Motor; from the dorsal scapular nerve (nerve to rhomboides, C5) Sensory; proprioceptive fibers from C3 and C4 Action; 1) Elevation of shoulder girdle (with upper fibers of trapezius) 2) Downward rotation of scapula 3) Retraction of scapula (with rhomboides) Origin; Rhomboideus minor; from spines of 7th cervical and 1st thoracic vertebrae, and their supraspinous ligament Rhomboideus minor M. Rhomboideus major; from spines of 2nd, 3rd, 4th and 5th thoracic vertebrae, and Rhomboideus their supraspinous ligament major M. Insertion; Rhomboideus minor; into dorsal surface of medial border of scapula, opposite the root of the spine Rhomboideus major; into dorsal surface of medial border of scapula, from the root of the spine to the inferior angle Nerve supply; from the dorsal scapular nerve (nerve to rhomboides, C5) Action; Dorsal scapular 1) Downward rotation of scapula (with levator nerve scapulae) 2) Retraction of scapula (with middle fibers of trapezius)  Suprasinatus There is a group of 6 muscles muscle surrounding the shoulder joint, extending from the scapula to the humerus: Infrasinatus muscle 1) Deltoid Teres minor 2) Supraspinatus muscle 3) Infraspinatus Teres major 4) Teres minor muscle Deltoid muscle 5) Teres major 6) Subscapularis Subscapularis muscle  Subscapularis It fills subscapular fossa of the scapula. muscle It forms the major part of posterior wall of axilla Origin: Medial 2/3 of subscapular fossa of scapula Insertion: Lesser tuberosity of humerus Origin of Insertion of subscapularis subscapularis muscle from medial muscle into lesser 2/3 of subscapular tuberosity of fossa humerus Insertion: Lesser tuberosity of humerus Origin: Medial 2/3 of subscapular fossa Nerve supply: Upper & lower subscapular nerves (C5, 6 – posterior cord of brachial plexus) Action: 1) Adduction & medial rotation of arm 2) Stabilization of anterior aspect of shoulder joint (through the rotator cuff) Line of pull of subscapularis muscle Why it is called subscapularis although it lies in front of the scapula? It was first described in tetrapod animals, where the ventral surface of the scapula faces downwards Origin: Medial 2/3 of supraspinous fossa Supraspinatus muscle Insertion: Highest impression on the greater tuberosity of humerus Nerve supply: Suprascapular nerve Suprascapular nerve (C5, 6 – upper trunk of brachial plexus) Supraspinatus muscle Action: 1) Initiates abduction of arm from 0-15° 2) Stabilization of head of humerus in the glenoid cavity during abduction Origin: Medial 2/3 of infraspinous fossa Infraspinatus muscle Insertion: Middle impression on the greater tuberosity of humerus Nerve supply: Suprascapular nerve Suprascapular nerve (C5, 6 – upper trunk of brachial plexus) Infraspinatus muscle Action: 1) Adduction and lateral rotation of arm 2) Stabilization of head of humerus in the glenoid cavity during abduction Origin: Upper 2/3 of dorsal surface of lateral border of scapula Insertion: Lowest impression on the greater tuberosity of humerus Teres minor muscle Nerve supply: Axillary (circumflex) nerve Axillary (circumflex) nerve (C5, 6 – posterior cord of brachial plexus) Teres minor muscle Action: 1) Abduction and lateral rotation of arm 2) Stabilization of head of humerus in the glenoid cavity during abduction Origin: Lower 1/3 of dorsal surface of lateral border of scapula Teres major muscle Insertion: Medial lip of bicipital groove of humerus  Insertion of pectoralis major into the lateral Note: teres major arises from the lip of the bicipital groove of humerus back of the scapula, but is Insertion of latissimus dorsi into the floor inserted into the front of the of the bicipital groove of humerus humerus, so it draws humerus backwards (i.e. extension) and Insertion of teres major into the medial lip of the bicipital groove of humerus rotates it towards the midline (i.e. medial rotation) Latissimus dorsi M. Nerve supply: Lower subscapular nerve (C5, 6 – posterior cord of brachial plexus) Lower subscapular nerve Teres major muscle Action: 1) Abduction and medial rotation of arm 2) Stabilization of head of humerus in the glenoid cavity during abduction Capsule of shoulder joint is weak and lax, so shoulder joint is liable for dislocation Tendons of subscapularis, supraspinatus, infraspinatus and teres minor help to steady head of humerus in the glenoid cavity during movements of the arm. The tendons of these 4 muscles also blend with capsule of shoulder joint to strengthen it, forming the “Musculo- tendinous Cuff” or “Rotator Cuff”.  Supraspinatus M. Subscapularis M. Infraspinatus M. Teres minor M. Subscapularis M. The triangular thick muscle that forms the rounded contour of the shoulder. Origin: V-shaped origin Anterior fibers; from Middle fibers; from Posterior fibers; from anterior border of lateral border of lower lip of crest of lateral 1/3 of clavicle acromion process spine of scapula Origin of deltoid and Insertion of Trapezius V-shaped origin of deltoid embraces the V-shaped insertion of trapezius Trapezius M. Deltoid M.  Insertion: Into the deltoid tuberosity at the middle of the lateral surface of the shaft of the humerus The middle fibers are multipennate, while the anterior and posterior fibers are nearly parallel. Deltoid tuberosity of humerus  Thoraco-acromial artery Deltopectoral groove: Cephalic vein It is the groove between the adjacent Deltoid muscle borders of deltoid and pectoralis major muscles. Its upper end just below the clavicle is referred to as the “infraclavicular fossa”. Deltopectoral lymph nodes It lodges the following structures: Cephalic 1. Uppermost part of cephalic vein vein 2. Deltoid branch of the thoraco- acromial artery Pectoralis major 3. Deltopectoral lymph nodes muscle  Infraclavicular fossa Deltopectoral groove Deltoid branch of Cephalic acromiothoracic vein artery Nerve supply: Axillary (circumflex) nerve (C5, 6 – posterior cord of brachial plexus)  Antero-posterior axis of Anterior adduction/abduction (clavicular) fibers Middle (acromial) fibers Posterior (spinal) fibers Antero-posterior axis of adduction/abduction Action: 1) Anterior fibers; flexion and medial rotation of arm 2) Middle fibers; abduction of arm from 15-90° 3) Posterior fibers; extension and lateral rotation of arm Action of anterior fibers of deltoid: flexion and medial rotation of arm Action of middle fibers of deltoid: abduction of arm from 15-90° Action of posterior fibers of deltoid: extension and lateral rotation of arm Combined action of middle and posterior fibers of deltoid Clinical importance: injury of axillary (circumflex) nerve causes paralysis of deltoid muscle, resulting in loss of abduction of shoulder joint from 15-90° with flat shoulder deformity  Long head of triceps M. Surgical neck of humerus Subscapularis M. Quadrangular space Upper triangular space Lower triangular space Teres major M.  Quadrangular space Lower triangular space Upper triangular space  Quadrangular Space Boundaries: Above; subscapularis (seen from in front), teres minor (seen from behind) and capsule of shoulder joint Below; teres major Medially; long head of triceps Laterally; surgical neck of humerus Contents: 1. Axillary (circumflex) nerve 2. Posterior circumflex humeral vessels Posterior circumflex humeral artery Axillary (circumflex) nerve  Upper (Medial) Boundaries: Triangular Space Above; subscapularis (seen from in front), teres minor (seen from behind) Below; teres major Laterally; long head of triceps Contents: Subscapularis M. Circumflex scapular artery Long head of triceps M. Teres major M. Circumflex scapular artery  Lower (Lateral) Triangular Space Boundaries: Above; teres major Medially; long head of triceps Profunda brachii artery Laterally; shaft of humerus Contents: 1. Radial nerve 2. Profunda brachii vessels Radial nerve