PCL 4 - MUSCLES OF THE SHOULDER

ANTERIOR AXIOAPPENDICULAR MUSCLES

PECTORALIS MAJOR

1. Proximal Attachment
Clavicular head: anterior surface of medial half of clavicle Sternocostal head: anterior surface of sternum, superior six costal cartilages, aponeurosis of external oblique muscle

2. Distal Attachment
Lateral lip of intertubercular sulcus of humerus

3. Innervation
Lateral and medial pectoral nerves; clavicular head (C5, C6), sternocostal head (C7, C8, T1)

4. Main Action
Adducts and medially rotates humerus; draws scapula anteriorly and inferiorly
Acting alone, clavicular head flexes humerus and sternocostal head extends it from the flexed position


PECTORALIS MINOR

1. Proximal Attachment
3rd-5th ribs near their costal cartilages

2. Distal Attachment
Medial border and superior surface of coracoid process of scapula

3. Innervation
Medial pectoral nerve (C8, T1)

4. Main Action
Stabilizes scapula by drawing it inferiorly and anteriorly against thoracic wall


SUBCLAVIUS

1. Proximal Attachment
Junction of 1st rib and its costal cartilage

2. Distal Attachment
Inferior surface of middle third of clavicle

3. Innervation
Nerve to subclavius (C5, C6)

4. Main Action
Anchors and depresses clavicle


SERRATUS ANTERIOR

1. Proximal Attachment
External surfaces of lateral parts of 1st-8th ribs

2. Distal Attachment
Anterior surface of medial border of scapula

3. Innervation
Long thoracic nerve (C5, C6, C7)

4. Main Action
Protracts scapula and holds it against thoracic wall; rotates scapula




POSTERIOR AXIOAPPENDICULAR MUSCLES

i.Superficial posterior axioappendicular (extrinsic shoulder) muscles

TRAPEZIUS

1. Proximal Attachment
Medial third of superior nuchal line; external occipital protuberance; nuchal ligament; spinous processes of C7-T12 vertebrae

2. Distal Attachment
Lateral third of clavicle; acromion and spine of scapula

3. Innervation
Spinal accessory nerve (CN XI) (motor fibers) and C3, C4 spinal nerves (pain and proprioceptive fibers)

4. Main Action
Descending part elevates; ascending part depresses; and middle part (or all parts together) retracts scapula; descending and ascending parts act together to rotate glenoid cavity superiorly


LATISSIMUS DORSI

1. Proximal Attachment
Spinous processes of inferior 6 thoracic vertebrae, thoracolumbar fascia, iliac crest, and inferior 3 or 4 ribs

2. Distal Attachment
Floor of intertubercular sulcus of humerus

3. Innervation
Thoracodorsal nerve (C6, C7, C8)

4. Main Action
Extends, adducts, and medially rotates humerus; raises body toward arms during climbing


ii. Deep posterior axioappendicular (extrinsic shoulder) muscles

LEVATOR SCAPULAE

1. Proximal Attachment
Posterior tubercles of transverse processes of C1-C4 vertebrae

2. Distal Attachment
Medial border of scapula superior to root of scapular spine

3. Innervation
Dorsal scapular (C5) and cervical (C3, C4) nerves

4. Main Action
Elevates scapula and tilts its glenoid cavity inferiorly by rotating scapula


RHOMBOID MINOR AND MAJOR

1. Proximal Attachment
Minor: nuchal ligament; spinous processes of C7 and T1 vertebrae
Major: spinous processes of T2-T5 vertebrae

2. Distal Attachment
Minor: smooth triangular area at medial end of scapular spine
Major: medial border of scapula from level of spine to inferior angle

3. Innervation
Dorsal scapular nerve (C4, C5)

4. Main Action
Retract scapula and rotate it to depress glenoid cavity; fix scapula to thoracic wall






SCAPULOHUMERAL (INTRINSIC SHOULDER) MUSCLES

DELTOID

1. Proximal Attachment
Lateral third of clavicle; acromion and spine of scapula

2. Distal Attachment
Deltoid tuberosity of humerus

3. Innervation
Axillary nerve (C5, C6)

4. Main Action
Clavicular (anterior) part: flexes and medially rotates arm
Acromial (middle) part: abducts arm
Spinal (posterior) part: extends and laterally rotates arm


SUPRASPINATUS

1. Proximal Attachment
Supraspinous fossa of scapula

2. Distal Attachment
Superior facet of greater tubercle of humerus

3. Innervation
Suprascapular nerve (C4, C5, C6)

4. Main Action
Initiates and assists deltoid in abduction of arm and acts with rotator cuff musclesb


INFRASPINATUS

1. Proximal Attachment
Infraspinous fossa of scapula

2. Distal Attachment
Middle facet of greater tubercle of humerus

3. Innervation
Suprascapular nerve (C5, C6)

4. Main Action
Laterally rotates arm; and acts with rotator cuff musclesb


TERES MINOR

1. Proximal Attachment
Middle part of lateral border of scapula

2. Distal Attachment
Inferior facet of greater tubercle of humerus

3. Ineervation
Axillary nerve (C5, C6)

4. Main Action
Laterally rotates arm; and acts with rotator cuff musclesb


TERES MAJOR

1. Proximal Attachment
Posterior surface of inferior angle of scapula

2. Distal Attachment
Medial lip of intertubercular sulcus of humerus

3. Innervation
Lower subscapular nerve (C5, C6)

4. Main Action
Adducts and medially rotates arm


SUBSCAPULARIS

1. Proximal Attachment
Subscapular fossa (most of anterior surface of scapula)

2. Distal Attachment
Lesser tubercle of humerus

3. Innervation
Upper and lower subscapular nerves (C5, C6, C7)

4. Main Action
Medially rotates arm; as part of rotator cuff, helps hold head of humerus in glenoid cavity



SOURCE : Moore K., Dalley A., Agur A., Clinically Oriented Anatomy, 6th ed. Baltimore, Lippincot Williams and Wilkin, 2010