Extrinsic muscles of the shoulder

Question 1

What are the extrinsic muscles of the shoulder (in general)?

Answer 1

The extrinsic muscles of the shoulder originate from the trunk, and attach to the bones of the shoulder – the clavicle, scapula or humerus. They are located in the back, and are also known as the superficial back muscles.
The muscles are organised into two layers – a superficial layer and a deep layer.

Question 2

Name all the Extrinsic muscles of the shoulder.

Answer 2

Trapezius, Latissimus Dorsi, Levator Scapulae, Rhomboid Major & Minor .

Question 3

Which muscles make up the superficial Extrinsic muscles?

Answer 3

Trapezius and Latissimus Dorsi.

Question 4

Where does the Trapezius muscle originate from?

Answer 4

Skull, Nuchal ligament and the Spinous process of C7-T12.

Question 5

Where does the Trapezius muscle attach to?

Answer 5

The clavicle, Acromion and Scapula spine.

Question 6

What innervates the Trapezius muscle?

Answer 6

Motor innervation is from the accessory nerve.

It also receives proprioception fibres from the C3&4 spinal nerves.

Question 7

What is the action of the Trapezius muscle?

Upper middle and lower fibres

Answer 7

Upper fibres of the trapezius elevate and rotate the scapula during abduction of the arm.
Middle fibres retract the scapula.
Lower fibres pull the scapula inferiorly.

Question 8

How can you test if the accessory nerve is damaged?

Answer 8

To test the accessory nerve, trapezius function can be assessed. This can be done by asking the patient to shrug his/her shoulders. Other clinical features of accessory nerve damage include muscle wasting, partial paralysis of the sternocleidomastoid, and an asymmetrical neckline.

Question 9

Where does Latissimus Dorsi originate from?

Answer 9

as a broad origin – arising from the spinous processes of T7-T12, iliac crest, thoracolumbar fascia and the inferior three ribs.

Question 10

Where does Latissimus Dorsi attach onto?

Answer 10

The fibres converge into a tendon that attaches to the intertubercular sulcus of the humerus.

Question 11

What innervates Latissimus Dorsi>

Answer 11

Thoracodorsal nerve.

Question 12

What are the actions of Latissimus Dorsi?

Answer 12

Extends, adducts and medially rotates the upper limb.

Question 13

Which muscles make up the deep extrinsic muscles of the shoulder?

Answer 13

Levator Scapulae, Rhomboid Major and Rhomboid Minor.

Question 14

Where does the Levator Scapulae muscle originate from?

Answer 14

Originates from the transverse processes of the C1-C4 vertebrae.

Question 15

Where does the Levator Scapulae muscle insert?

Answer 15

The medial border of the scapula.

Question 16

What innervates Levator Scapulae?

Answer 16

Dorsal scapular nerve.

Question 17

What is the action of Levator Scapulae?

Answer 17

Elevates the scapular.

Question 18

Where does the Rhomboid Major muscle originate from?

Answer 18

The spinous process pf T2-T5 vertebrae.

Question 19

Where does Rhomboid Major insert onto?

Answer 19

Medial border of the scapula, between the scapula spine and inferior angle.

Question 20

What innervates Rhomboid Major?

Answer 20

Dorsal scapula nerve.

Question 21

What are the actions of Rhomboid Major?

Answer 21

Retracts and rotates the scapula.

Question 22

Where does Rhomboid Minor originate from?

Answer 22

Originates from the transverse processes of the C1-C4 vertebrae

Question 23

Where does Rhomboid Minor insert?

Answer 23

The medial border of the scapula, at the level of the spine of scapula.

Question 24

What innervates Rhomboid Minor?

Answer 24

Dorsal scapular nerve.

Question 25

What are the actions of Rhomboid minor?

Answer 25

Retracts and rotates the scapula.