Week 7 Muscles Breakdown

Question 1

Deltoid Origin

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

Question 2

Deltoid Insertion

Answer 2

I: deltoid tuberosity of the humerus

Question 3

Deltoid Action

Answer 3

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 4

Coracobrachialis Origin

Answer 4

O: coracoid process of the scapula

Question 5

Coracobrachialis Insertion

Answer 5

I: medial surface of the mid-humeral shaft

Question 6

Coracobrachialis Action

Answer 6

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

Question 7

Pectoralis Major Origin

Answer 7

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

Question 8

Pectoralis Major Insertion

Answer 8

I: crest of the greater tubercle of the humerus

Question 9

Pectoralis Major Action

Answer 9

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 10

Latissimus dorsi origin

Answer 10

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

Question 11

Latissimus dorsi insertion

Answer 11

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

Question 12

Latissimus dorsi action

Answer 12

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

Question 13

Teres Major (lats little helper) origin

Answer 13

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

Question 14

Teres Major (lats little helper) insertion

Answer 14

I: Crest of the lesser tubercle of the humerus

Question 15

Teres Major action

Answer 15

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