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Muscles of the Shoulder Joint Conor McCollamLearning Objectives • Describe the origin, insertion, innervation and actions of the pectoralis major muscle and identify this muscle • Describe the innervation and action(s) of the pectoralis minor and serratus anterior muscles and identify these muscles • Describe the origin, insertion, innervation and action of the deltoid muscle and identify this muscle • Describe the innervation and action(s) of the trapezius, latissimus dorsi, rhomboid major, rhomboid minor and levator scapulae muscles- and identify these muscles • Describe the origin, insertion, innervation and action(s) of the rotator cuff group of muscles: supraspinatus, infraspinatus, teres minor, and subscapularis muscles – and identify these muscles • Describe the origin, insertion, innervation and actions of the teres major muscle – identify this muscle• Describe the origin, insertion, innervation and actions of the pectoralis major muscle and identify this muscle • Origin • Clavicular head anterior surface of Pectoralis Major medial half of clavicle • Sternocostal head: Anterior surface of sternum, superior six costal cartilages, aponeurosis of external oblique muscle • Insertion • Lateral lip of intertubercle sulcus of humerus • Innervation • Lateral and Medial pectoral nerves • Clavicular head (C5, C6) • Sternocostal head (C7, C8, T1) • Function • Adduct and medially rotate upper limb • Draw the scapula anteroinferiorly • Clavicular head also acts individually to flex the upper limbPectoralisMinor • Origin rd th • 3 – 5 ribs • Insertion • Medial border and superior surface of coracoid process of scapula • Innervation • Medial pectoral nerve (C8, T1) • Function • Stabilises the scapula by drawing it inferiorly and anteriorly against thoracic wallSerratus Anterior • Origin • External surfaces of lateral parts of 1st – 8 ribs Boxer’s muscle • Insertion • Anterior surface of medial border of scapula • Innervation • Long thoracic nerve (C5, C6, C7) • Function • Protract scapula and hold it against thoracic wall • Rotate the scapulaClinical Context • Damage to the long thoracic nerve • Paralyseserratus anterior • Protrudes out the back • Giving “winged appearance” • Commonly in injuries where upper limb is violently stretched• Describe the origin, insertion, innervation and action of the deltoid muscle and identify this muscleDeltoid • Origin • Lateral third of the clavicle • Acromion and spine of scapula • Insertion • Deltoid tuberosity of humerus • Innervation • Axillary nerve (C5, C6) • Function • Clavicular part: Flexes and medially rotates arm • Acrominal part: abducts arm (>15 degrees where it takes over from supraspinatus) • Spinal part: extends and laterally roatesthe arm• Describe the innervation and action(s) of the trapezius, latissimus dorsi, rhomboid major, rhomboid minor and levator scapulae muscles- and identify these muscles • Origin Trapezius • Medial third of superior Nuchal line • External occipital protuberance of skull • Nuchal ligament • Spinous processes of C7-T12 vertebrae • Insertion • Lateral third of clavicle • Acromion and spine of scapula • Innervation • Spinal accessory nerve (CNXI) • Function • Descending part: Elevates scapula • Ascending part: Depresses • Middle part: Retracts scapula • Ascending and descending act together to rotate glenoid cavity superiorlyLatissimus dorsi • Origin • Spinous processes of inferior 6 thoracic vertebrae (T6-T12) • Thoracic-lumbar fascia • Iliac crest Pectoralis Major • Inferior 3-4 ribs (rib 8-12) • Insertion Latissimus Dorsi • Floor of intertubercular sulcus of humerus Teres Major • Innervation • Thoracodorsal nerve (C6, C7, C8) • Function • Extend, adducts, and medially rotate humerus • Raises body towards arms during climbing Lady Between Two Majors Major Rhomboid Major and Minor • Origin • Spinous processes of T2-T5 vertebrae • Insertion • Medial Border of of scapula from level of spine to inferior angle Minor • Origin • Nuchal Ligment, spinous processes of C7- T1 vertebrae • Insertion • Smooth triangle area of medial end of scapular spine Both • Innervation • Dorsal scapula nerve (C4, C5) • Function • Retract scapula and rotate the glenoid cavity inferiorly • Fix scapula to thoracic wallLevator Scapulae • Origin • Posterior tubercle of transverse processes of C1-C4 vertebrae • Insertion • Medial border of scapular superior to root of scapular spine • Innervation • Dorsal scapular (C4, C5) • Cervical nerves (C3, C4) • Function • Elevate scapula and rotate its glenoid cavity inferiorly• Describe the origin, insertion, innervation and action(s) of the rotator cuff group of muscles: supraspinatus, infraspinatus, teres minor, and subscapularis muscles – and identify these musclesSupraspinatus • Origin • Supraspinous fossa of scapula • Insertion • Superior facet of greater tubercle of humerus • Innervation • Suprascapular nerve (C4, C5, C6) • Function • Imitates and assists deltoid in abduction of arm and acts with rotator cuff muscles (015 )Infraspinatus • Origin • Infraspinous fossa of scapula • Insertion • Middle facet of greater tubercle of humerus • Innervation • Suprascapular nerve (C5, C6) • Function • Laterally rotates armTeres Minor • Origin • Middle part of Lateral border of scapula • Insertion • humerusr facet of greater tubercle of • Innervation • Axillary nerve (C5, C6) • Function • Laterally rotates armSubscapularis • Origin • Subscapular fossa • Insertion • Lesser tubercle of humerus • Innervation • Upper and lower subscapular nerve (C5, C6, C7) • Function • Medially rotates armRotator Cuff Muscles SITS Help hold the humeral head in glenoid cavity• Describe the origin, insertion, innervation and actions of the teres major muscle – identify this muscleTeres Major • Origin • Posterior surface of inferior angle of scapula • Insertion • Medial lip of intertubercular sulcus of humerus • Innervation • Lower subscapular nerve (C5, C6) • Function • Adducts and medially rotates the arm Teres Major What nerve is damaged that leads to “winged scapula” appearance? A. Axillary nerve B. Short thoracic nerve MCQ C. Dorsal Scapular nerve D. Long Thoracic nerve E. Suprascapular nerve What muscle is paralysed as a result of this nerve damage A. Deltoid B. Levator Scapulae MCQ C. Supraspinatus D. Latissimus Dorsi E. Serratus Anterior What muscle attaches to the medial lip of the intertubercle sulcus of the humerus A. PectoralisMajor B. PectoralisMinor MCQ C. TeresMajor D. Latissimus Dorsi E. Serratus Anterior