Week VI Muscles

Question 1

Deltoid

Answer 1

O: Anterior fibers- lateral (one third of the) clavicle
Middle fibers- lateral acromion process of the scapula
Posterior fibers- spine of the scapula

I: deltoid tuberosity of the humerus

A: All fibers- abduct the shoulder at the glenohumeral joint

Anterior fibers- flex the shoulder at the glenohumeral joint
internally rotate the shoulder at the glenohumeral joint
horizontally adduct the shoulder at the glenohumeral joint

Posterior fibers- extend the shoulder at the glenohumeral joint
externally rotate the shoulder at the glenohumeral joint
horizontally abduct the shoulder at the glenohumeral joint

Question 2

Coracobrachialis

Answer 2

O: coracoid process of the scapula

I: medial surface of the mid-humeral shaft

A: flexes the shoulder at the glenohumeral joint
adducts the shoulder at the glenohumeral joint
horizontally adducts the shoulder at the glenohumeral joint

Question 3

Pectoralis Major

Answer 3

O: clavicular fibers- anteromedial (one half of the) clavicle Middle
sternal fibers- sternum and costal cartilage of ribs 1-6

I: crest of the greater tubercle of the humerus

A: All fibers- adduct the shoulder at the glenohumeral joint
internally rotate the shoulder at the glenohumeral joint

Clavicular fibers- flex the shoulder at the glenohumeral joint
horizontally adduct the shoulder at the glenohumeral joint

Sternal fibers- extend the shoulder at the glenohumeral joint

Question 4

Latissimus dorsi

Answer 4

O: spinous processes (SPs) of T7-L5, posterior sacrum, posterior iliac crest and posterior ribs 10-12 all via the thoracolumbar fascia

I: intertubercular (bicipital) groove (just on the inside of the lesser tubercle) of the humerus

A: internally rotates the shoulder at the glenohumeral joint
adducts the shoulder at the glenohumeral joint
extends the shoulder at the glenohumeral joint

Question 5

Teres Major

Answer 5

O: inferior angle and inferior (one third of the) lateral border of the scapula

I: crest of the lesser tubercle of the humerus

A: internally rotates the shoulder at the glenohumeral joint
adducts the shoulder at the glenohumeral joint
extends the shoulder at the glenohumeral joint