Scapulohumeral Muscles (Intrinsic Muscles) MA

Question 1

Teres Minor (Rotator Cuff Muscle)
(origin, insertion, innervation, main action)

Answer 1

Origin: Superior 2/3rds of the lateral border of the scapula

Insertion: inferior facet of the greater tubercle of the humerus

Innervation: Axillary nerve

Main Action: laterally (externally) rotates the glenohumetal joint; helps to hold the humoral head in the glenoid cavity of the scapula.

Question 2

Subscapularis Muscle (Rotator Cuff Muscle) (Origin, insertion, innervation, main action)

Answer 2

Origin: Subscapular fossa (costal surface) of scapula

Insertion: Lesser tubercle of the humerus and medial lip of the intertubercular sulcus of the humerus

Innervation: upper and lower subscapular nerves (C5-C7)

Main Actions: medially rotates the glenohumeral joint cavity

Question 3

Teres Major (Origin, insertion, innervation, main action)

Answer 3

Origin: inferior part of the lateral and dorsal surface of the inferior angle of the scapula

Insertion: medial lip of the intertubercular sulcus of the humerus

Innervation: lower subscapular nerve (C5-C7)

Main action: adducts and medially rotates the glenohumeral joint.

Question 4

Deltoid (Origin, insertion, innervation, main action)

Answer 4

Origin: lateral 1/3 of the clavicle, acromion and spine of the scapula

Insertion: Deltoid tuberosity of the humerus

Innervation: axillary nerve

Main action: anterior portion: flexes and medially rotates the glenohumeral joint
Middle portion: abducts the glenohumeral joint.
Posterior portion: extends and laterally rotates the glenohumeral joint

Question 5

Infraspinatus muscle (Rotator Cuff Muscle) (Origin, insertion, innervation, main action)

Answer 5

Origin: infraspinous fossa of the scapula

Insertion: middle facet of the greater tubercle of the humerus

Innervation: Suprascapular nerve

Main action: laterally (externally) rotates the glenohumeral joint; help to hold the humeral head in the glenoid cavity of the scapula.

Question 6

Supraspinatus (Rotator Cuff Muscle) (Origin, insertion, innervation, main action)

Answer 6

Origin: Supraspinous fossa of the scapula

Insertion: Superior facet of the greater tubercle of the humerus

Innervation: Suprascapular nerve

Main action: Initiates and assists the deltoid in abduction glenohumeral joint and acts with other rotator cuff muscles to stabilize the shoulder joint.