8.2 Posterior Shoulder and Arm

Question 1

Identify the deltoid muscle, its attachments, innervation, and function.

Answer 1

• Attaches from clavicle, acromion, and spine of scapula onto deltoid tuberosity.
• Innervated by Axillary Nerve (C5-C6).
• Function: abduct the arm. Also weak flex/extend and internal/external rotation.

Question 2

Identify the teres minor muscle, its attachments, innervation, and function.

Answer 2

• Proximal attachment at the middle part of lateral border of scapula, distal attachment at inferior facet of greater tubercle of humerus
• Innervated by the axillary nerve (C5-C6).
• Actions: lateral rotation and rotator cuff stabilization

Question 3

Identify the teres major muscle, its attachments, innervation, and function.

Answer 3

• Proximal attachment at the posterior surface of inferior angle of scapula, distal attachment at medial lip of the intertubercular groove of humerus
• Innervated by the lower sub scapular nerve (C6).
• Actions: adducts and medially rotates the arm (not a rotator cuff muscle)

Question 4

Identify the latissimus dorsi, its attachments, innervation, and function.

Answer 4

• Originates from transverse processes of vertebrae/iliac crest. Inserts into inter tubercular groove of humerus.
• Innervated by Throacodorsal n. (C6-C8).
• Actions: Adducts and internally rotates the arm.

Question 5

Identify the triceps brachii, its attachments, innervation, and function.

Answer 5

• Proximal attachment at the infraglenoid tubercle of scapula (long head), posterior surface of humerus superior to radial groove (lateral head), and posterior surface of humerus inferior to radial groove (medial head). Distal attachment to proximal end of olecranon of ulna
• Innervated by the radial nerve with possible contribution of axillary to long head (posterior compartment)
• Actions: extension of forearm. At glenohumeral joint extends arm and resists dislocation

Question 6

Identify and describe the Quadrangular space.

What are its borders and what passes thru this space?

Answer 6

Quadrangular space: contains axillary nerve and posterior humeral circumflex artery
Lateral border –humerus
Medial border –long head of triceps brachii
Superior border –teres minor
Inferiorly –teres major

Question 7

Identify and describe the Triceps hiatus (Triangular Interval).
What passes thru this space and what are its borders?

Answer 7

Triangular Interval contains the radial nerve and deep brachial artery
Lateral border –lateral head of the triceps
Medial border –long head of the triceps
Superior border –teres major

Question 8

Identify the Triangular space. What passes thru this space and what are its borders?

Answer 8

Triangular space: contains the scapular circumflex artery
Lateral border –long head of the triceps
Superior border –teres minor
Inferior border –teres major

Question 9

Identify the infraspinatus muscle, its attachments, innervation, and function.

Answer 9

• Proximal attachment in the infraspinatus fossa of the scapula, distal attachment on the middle facet of the great tubercle of the humerus
• Innervated by the supra scapular nerve (C5-C6).
• Actions: lateral rotation and rotator cuff stabilization

Question 10

Identify the supraspinatus muscle, its attachments, innervation, and function.

Answer 10

• Proximal attachment in the supraspinous fossa of scapula, distal attachment on the superior facet of the greater tubercle of the humerus
• Innervated by the supra scapular nerve (C5-C6).
• Actions: abduction and rotator cuff stabilization

Question 11

Describe the scapular notch.
Identify the relative locations of the supra scapular artery, superior transverse scapular ligament, and supra scapular nerve in this region.

Answer 11

The suprascapular notch (or scapular notch) is a notch in the superior border of the scapula, just medial to the base of the coracoid process.

• The suprascapular artery passes over the superior transverse scapular ligament, which spans the scapular notch.
• The suprascapular nerve passes under the superior transverse scapular ligament.

Question 12

Identify the subscapularis muscle, its attachment, innervation, and function.

Answer 12

• Proximal attachment in the subscapular fossa, distal attachment at the lesser tubercle of the humerus
• Innervated by the upper and lower sub scapular nerves (C5, C6).
• Actions: medial rotation, adduction, and rotator cuff stabilization

Question 13

Identify the anconeus muscle, its attachments, innervation, and function.

Answer 13

• Proximal attachment at lateral epicondyle of humerus, distal attachment to lateral surface of olecranon and superior part of posterior surface of ulna
• Innervated by the radial nerve (posterior compartment) (C5-C8).
• Actions: assists in extension of forearm, and stabilizes elbow joint.

Question 14

Identify the levator scapulae, its attachments, innervation, and function.

Answer 14

• Originates from transverse processes of C1-C4. Inserts Superior part of Medial border of scapula.
• Innervated by dorsal scapular n (C5).
• Actions: elevates and rotates scapula.