Intrinsic muscles of the shoulder

Question 1

Name all the intrinsic muscles of the shoulder.

Answer 1

Deltoid, Teres major, Supraspinatus, infraspinatus, subscapularis and teres minor.

Question 2

Name all the rotator cuff muscles.

Answer 2

Supraspinatus, Infraspinatus, Subscapularis and Teres minor.

Question 3

What are rotator cuff muscles?

Collective function ETC

Answer 3

They are a group of 4 muscles, that originate from the scapular and attach to the humeral head.
Their collective function is to pull the humeral head into the glenoid fossa. Thus providing additional stability to the joint.

Question 4

Where does the Deltoid originate from, and where does it insert?

Answer 4

Origin: Lateral third of the clavicle, the acromion and the spine of the scapular..

Insertion: Deltoid tuberosity on the lateral aspect of the humerus.

Question 5

What innervates the Deltoid?

Answer 5

Axillary nerve.

Question 6

What is the action of the Deltoid?

Anterior, Posterior and middle fibres

Answer 6

Anterior fibres: Flexion and medial rotation.
Posterior fibres : Extension and lateral rotation
Middle fibres: Major abductor of the arm. (Takes over from supraspinatus, which abducts the first 15 degrees.

Question 7

Where does Teres Major originate and where does it insert?

Answer 7

Origin: Posterior surface of the inferior angle of the scapular.
Insertion: Medial lip of the intertubercular groove of the humerus.

Question 8

What innervates Teres Major?

Answer 8

Lower subscapular nerve.

Question 9

What is the action of Teres Major?

Answer 9

Adducts the shoulder and medially rotates the arm.

Question 10

Where does Supraspinatus originate from, and where does it insert?

Answer 10

Origin: Supraspinous fossa of the scapular.

Insertion: Attaches to the greater tubercle of the humerus.

Question 11

What innervates the Supraspinatus?

Answer 11

Suprascapular nerve.

Question 12

What is the action of Supraspinatus?

Answer 12

Abducts the arm 0-15 degrees and assists the deltoid from 15-90 degrees.

Question 13

Where does Infraspinatus originate from and where does it insert?

Answer 13

Origin: Infraspinatus fossa of the scapular.

Insertion: Attaches to the greater tubercle of the humerus.

Question 14

What innervates Infraspinatus?

Answer 14

Suprascapular nerve.

Question 15

What is the action of Infraspinatus?

Answer 15

Laterally rotates the arm.

Question 16

Where does Subscapularis originate from and where does it insert?

Answer 16

Origin: Subscapular fossa on the costal surface of the scapular.

Insertion: Lesser tubercle
of the humerus.

Question 17

What innervates Subscapularis?

Answer 17

Upper & Lower Subscapular nerve.

Question 18

What is the action of Subscapularis?

Answer 18

Medially rotates the arm.

Question 19

Where does Teres minor originate from and where does it insert?

Answer 19

Origin: Posterior surface of the scapular, adjacent to the lateral border.

Insertion: Greater tubercle of the humerus.

Question 20

What innervates Teres minor?

Answer 20

Axillary nerve.

Question 21

What is the action of Teres minor?

Answer 21

Laterally rotates the arm.

Question 22

What links the intrinsic muscles of the shoulder / what do they have in common to be considered a group.

Answer 22

They all originate from the scapula and/or clavicle, and attach to the humerus.