5 Muscles (Scapulohumeral - Intrinsic)

Question 1

What are the 6 muscles of the scapulohumeral (intrinsic) compartment?

Answer 1

The 4 rotator cuff muscles:
supraspinatus
infraspinatus
teres minor
subscapularis

Deltoid
Teres Major

Question 2

Practice an oral presentation of the supraspinatus muscle.

Answer 2

Location: part of the rotator cuff muscle group. Runs along the posterior surface of the scapula inferior to the scapula spine, through the subacromial space, and attaches tot he humerus.

Function:
initiates shoulder abduction (first 15 degrees)
assists deltoid in shoulder abduction beyond 15 degrees
stabilises the humeral head and resists superior displacement of the humerus

PA: supraspinous fossa on the posterior surface of the scapula, superior to spine of the scapula

DA: greater tubercle of the humerus (superior facet)

NS: suprascapular nerve (C5-C6)

Question 3

Practice an oral presentation of the infraspinatus muscle.

Answer 3

Location: part of the scapulohumeral muscle compartment, and one of the 4 rotator cuff muscles. Runs from the posterior surface of the scapula inferiorly to the spine of the scapula, and attaches to the humerus.

Function:
external rotation of the humerus
stabilises the GH joint

PA:
infraspinous fossa of the scapula, inferiorly to the spine of the scapula on the posterior surface

DA: greater tubercle of the humerus (middle facet)

NS: suprascapular nerve (C5-6)

Question 4

Practice an oral presentation of the teres minor muscle.

Answer 4

Location: part of the scapulohumeral (intrinsic) muscle compartment. One of the 4 rotator cuff muscles. Runs between the lateral border of the scapula to the humerus. Often blends with the infraspinatus

Function:
external rotation of the humerus
stabilizes the GH joint

PA:
lateral border of the scapula, middle component

DA: greater tubercle of the humerus (inferior facet)

NS: axillary nerve (C5-6)

Question 5

Practice an oral presentation of the subscapularis muscle

Answer 5

Location: part of the scapulohumeral muscle compartment, one of the 4 rotator cuff muscles. The only internal rotator muscle in the rotator cuff muscle group, produces an equal force to the other 3 rotator cuff muscle groups combined.

Function: internal rotation of the humerus, stabilizes the GH joint

PA: subscapular fossa, anterior surface of the scapula

DA: lesser tubercle of the humerus

NS: upper and lower subscapular nerve (C5-7)

Question 6

Practice an oral presentation of the deltoid muscle

Answer 6

Location: part of the scapulohumeral (intrinsic) muscle compartment, located on the superolateral surface of the shoulder.

Structure: multipennate muscle. three components to deltoid: anterior, middle and posterior deltoids. components can act independently or together

Function:

anterior: flexes and internally rotates humerus
middle: abducts humerus (supraspinatus initiates abduction and performs the first 15 degrees of abduction), posterior: extends and externally rotates humerus

PA: clavicle, acromion process, and spine of scapula

DA: deltoid tuberosity on lateral component of humerus

NS: axillary nerve (C5-6)

Question 7

Practice an oral presentation of the teres major muscle

Answer 7

Location: part of the scapulohumeral (intrinsic) muscle compartment.

Function: internal rotation of the humerus, adduction of the humerus. Forms part of the posterior wall of the axilla.

PA: lateral border of the scapula, inferior aspect.

DA: bicipital groove of humerus

NS: lower subscapular nerve (C5-6)