Muscle Chart: Posterior Shoulder Girdle

Question 1

Deltoid (posterior fibers)

Origin, Insertion, Innervation, Blood Supply

Answer 1

• Origin: Distal acromion and spine of scapula
• Insertion: Deltoid tuberosity of the humerus
• Innervation: Axillary nerve (C5, 6)
• Blood Supply: Deltoid artery from thoracoacromial trunk, circumflex humeral artery

Question 2

Teres Major

Origin, Insertion, Innervation, Blood Supply

Answer 2

• Origin: Inferior angle and lower 1/3 of scapula
• Insertion: Crest of lesser tubercle of humerus
• Innervation: Lower subscapular nerve (C5, 6, 7)
• Blood Supply: Thoracodorsal artery

Question 3

Infraspinatus (part of rotator cuff)

Origin, Insertion, Innervation, Blood Supply

Answer 3

• Origin: Infraspinous fossa
• Insertion: Greater tubercle of the humerus
• Innervation: Suprascapular nerve (C4, 5, 6)
• Blood Supply: Suprascapular artery

Question 4

Teres Minor Movements

Answer 4

• Laterally rotates and adducts the shoulder
• Stabilizes the head of the humerus in glenoid

Question 5

Teres Minor (part of rotator cuff)

Origin, Insertion, Innervation, Blood Supply

Answer 5

• Origin: Proximal upper 2/3 of the lateral scapula
• Insertion: Greater tubercle of the humerus
• Innervation: Axillary nerve (C5, 6)
• Blood Supply: Circumflex scapular artery

Question 6

Teres Major Movements

Answer 6

• Extends
• Adducts
• Medially rotation of shoulder

Question 7

Deltoid Movements

Answer 7

• Abducts the shoulder (along with the middle and anterior portions)
• Posterior Fibers: extend, laterally rotate and horizontally abduct the shoulder

Question 8

Infraspinatus Movements

Answer 8

• Laterally rotates and adducts the shoulder
• Stabilizes the head of humerus in glenoid (same as teres minor)