Superficial Posterior Muscles - Latissimus dorsi, teres major
Lateral Muscles - deltoid
Rotator Cuff - deep stabilising group
Pectoralis Major (Superficial Anterior Muscles)
Large powerful muscle covering the anterior chest wall
Arises from 2 heads
Clavicular head – anterior border of medial ½ of clavicle
Sternal head – body of sternum, costal cartilages of upper 6 ribs, aponeurosis of the external abdominal oblique (rectus sheath)
2 lamina cross to form flat tendon which inserts into the lateral lip of intertubercular sulcus
A: Adduction and medial rotation of glenohumeral joint. Clavicular head will produce flexionof the shoulder. Sternal head will extend form a flexed position
NS: Medial & lateral pectoral nerves (C5-T1)
Latissimus Dorsi (Superficial Posterior Muscles)
Large powerful muscle that unites the pelvic and pectoral girdles
From thoracolumbar fascia, spinous processes of T6-L5, outer lip of posterior 1/3 of iliac crest
To floor of intertubercular sulcus (may attach to lower 3 or 4 ribs and occasionally to inferior angle of the scapula)
A: Extension, adduction and medial rotation of shoulder – often termed the climbing muscle due to its action
NS: Thoracodorsal nerve (C6, 7 & 8)
Teres Major
Short powerful muscle on posterior aspect of shoulder
Arises from the posterior aspect of the inferior angle and lower part of lateral border
Passes though the axilla forming the posterior wall to insert onto the medial lip of the intertubercular sulcus
A: medial rotation, extension and adduction
NS: Lower subscapular nerve (C6,7)
Deltoid
Thick powerful muscle forming the contour of the shoulder
Divided into 3 sections
Anterior fibres – from anterior order of lateral 1/3 of clavicle
Middle fibres from lateral border of acromion process
Posterior fibres from the inferior border of the spine of the scapula and fascia covering infraspinatus
All 3 heads converge to form a common tendon which inserts into the deltoid tuberosity on the humerus
Actions
Ant – flexion/medial rotation
Middle – abduction
Posterior – extension/lateral rotation
NS: Axillary nerve (C5, 6)
The Rotator Cuff
Group of 4 muscles that acts as ‘musculotendinous ligaments’ of the shoulder
Act as fingers gripping the head of humerus holding it into the glenoid fossa during movements
Key stabilisers of the glenohumeral joint
1. Supraspinatus
Most superior of rotator cuff - provides superior support to GHJ
Arises from the medial 2/3s of the supraspinous fossa
Passes laterally under the acromion process (separated by subacromial burse) to insert into the superior facet on the greater tubercle
A: Abduction of the GHJ
NS: Suprascapular nerve (C4,5 & 6)
2. Infraspinatus
Forms posterior element of cuff with teres minor
Arises from medial 2/3s of infraspinous fossa
Passes under posterior acromial angle to insert into the middle facet on the greater tubercle – separated from scapula neck by infraspinatus bursa
A: Lateral rotation of GHJ
NS: Suprascapular nerve (C4,5 & 6)
3. Teres Minor
Assists infraspinatus in providing posterior stability to GHJ
Arises from the upper 2/3s of lateral border of the scapular
Inserts into the lower facet of the greater tubercle
A: Adduction and lateral rotation - prevents upward subluxation of humerus
NS: Axillary nerve (C(4),5,6)
4. Subscapularis
Stabilises the anterior aspect of the GHJ
Lies between the scapula and thoracic cage
Arises from the medial 2/3s of the subscapular fossa
Inserts into the lesser tubercle - separated fthe the anterior GHJ by the subscapualr bursa
