The Shoulder

Label the Shoulder  The shoulder is made up of three bones Humerus Scapula Clavicle  Humerus – upper arm bone  Scapula – shoulder blade  Clavicle – collar bone

Anatomy of the Shoulder  The head of the humerus fits into a rounded socket in the scapula  A combination of muscles and tendons keeps the humerus centered in the socket

The Shoulder Girdle  The muscles of the shoulder girdle act on the scapula, primarily to stabilize it.  There are six major muscles that anchor the scapula. –Four posterior muscles (Trapezius, Rhomboid Major, Rhomboid Minor, Levator Scapulae) –Two anterior muscles (Pectoralis Minor, Serratus Anterior)

The Shoulder Girdle Since the scapula has no bony articulations with the rib cage it essentially floats The main function of the shoulder girdle muscles is to fixate the scapula When the scapula is immobilized it serves as a point of origin for the muscles of the humerus (upper arm bone)

Posterior Muscles of the Shoulder Girdle

Anterior Muscles of the Shoulder Girdle

Major Muscles That Act at the Shoulder Girdle

The Shoulder  The shoulder joint is the most mobile joint in the body.  There are a total of nine muscles that cross the shoulder joint (inserting on the humerus). –Seven muscles originate from each scapula. Supraspinatus, infraspinatus, subscapularis, teres minor, deltoid, teres major, and coracobrachialis) –Two muscles originate from the axial skeleton (no attachment on the scapula). Pectoralis major, latissiumus dorsi

The Shoulder Anterior Deltoid and Pectoralis Major

The Shoulder- Latissiumus Dorsi, Pectoralis Major and Deltoid, Lateral View

The Shoulder – Posterior Muscle of the Shoulder Joint

The Rotator Cuff  Four of the muscles that act at the shoulder are commonly called the rotator cuff.  The rotator cuff’s primary stabilizing function is to hold the humeral head in the glenoid fossa to prevent subluxation (dislocation).  The muscles of the rotator cuff can be remembered using the acronym SITS: –Supraspinatus –Infraspinatus –Teres minor –Subscapularis

The Rotator Cuff – Anterior View

The Rotator Cuff – Posterior View

Coracobrachialis

Major Muscles That Act at the Shoulder