All of these fibers insert on the lateral third of the clavicle, acromion process and spine of the scapula.ДЄs a whole, the trapezius upwardly rotates the scapula.

The trapezius as a whole originates from the external occipital protuberance, ligamentum nuchae (the ligament of the back of the neck), and spinous processes of the last cervical and all thoracic vertebrae. Because of the many origins of the trapezius, each of these areas of fibers performs a different action. The trapezius is the easily distinguishable muscle superior muscle of the neck/back, is divided into three different groups: the superior fibers, middle fibers, and inferior fibers. Of even greater concern is the subscapularis' job of preventing anterior dislocation of the head of the humerus. The subscapularis originates from the subscapular fossa of the scapula and inserts on the lesser tubercle of the humerus. The only anterior muscle of the rotator cuff is the subscapularis. The teres major assist the latissimus dorsi in extension, adduction, and medial rotation of the arm, but only when there is resistance against these movements, such as during weight training. The teres major originates from the inferior angle of the scapula and inserts on the medial lip of the intertubercular groove of the humerus. Though the teres major originates near the teres minor, its function is more closely paired with latissimus dorsi due to its insertion. They also maintain the position of the head of the humerus during other arm movements. The infraspinatus and teres minor on the other hand, work together as lateral rotators of the arms. The supraspinatus acts alone and assists in shoulder abduction. All three muscles insert on the greater tubercle of the humerus. Finally, the teres minor originates from the lateral border of the scapula. The infraspinatus originates from the infraspinous fossa of the scapula. It originates from the supraspinous fossa of the scapula. The most superior of the three posterior rotator cuff muscles is the supraspinatus. Posterior Muscles-Supraspinatus, Infraspinatus, and Teres Minor

Three of the four muscles originate posteriorly, with only one originating anteriorly.

It is made up of four muscles, all of which assist in the movements of the deltoid. The rotator cuff aids in stabilizes the shoulder joint by holding the head of the humerus in the glenoid fossa of the scapula. Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis The anterior fibers flex and medially rotate the arm, the middle fibers abduction the arm, and the posterior fibers extend and laterally rotate the arm. All three portions of the deltoid muscle insert on the deltoid tuberosity of the humerus.Д«ecause the three portions of the deltoid each pass over a different part of the glenohumeral joint (shoulder), they each have a distinct action. The anterior deltoid originates from the lateral third of the clavicle, the middle deltoid from the acromion process, and the posterior deltoid from the spine of the scapula. Like many other muscles in the body, the deltoid is divided into distinct fiber portions. Nothing Stands Out Like A Nice Pair Of Deltoids.

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