Muscle Origins, Insertions, and Actions

Muscle Anatomy and Functions

Major Muscles of the Upper Body

Coracobrachialis

• Origin: Coracoid process of scapula

• Insertion: Medial surface of humerus

• Action:

  • Flexes upper arm

  • Adducts upper arm

  • Rotates upper arm medially

Deltoid

• Origin: Acromion process and spine of scapula

• Insertion: Deltoid tuberosity of humerus

• Action:

  • Abducts upper arm

  • Flexes upper arm

  • Extends upper arm

Infraspinatus

• Origin: Infraspinous fossa

• Insertion: Greater tubercle of humerus

• Action:

  • Extends upper arm

  • Rotates upper arm laterally

Latissimus Dorsi

• Origin: Spinous processes of lower 6 thoracic (T) vertebrae, all lumbar (L) and sacral (S) vertebrae, iliac crest, ribs

• Insertion: Intertubercular sulcus of humerus

• Action:

  • Adducts upper arm

  • Rotates arm medially

Levator Scapulae

• Origin: Transverse processes of cervical (C) vertebrae C1-C4

• Insertion: Superior medial border of scapula

• Action:

  • Elevates scapula

Pectoralis Major

• Origin: Clavicle, sternum, and ribs 2-6

• Insertion: Intertubercular sulcus of humerus

• Action:

  • Flexes shoulder

  • Adducts upper arm

  • Rotates upper arm medially

Pectoralis Minor

• Origin: Sternal end of ribs 3-5

• Insertion: Coracoid process of scapula

• Action:

  • Depresses and protracts scapula

  • Elevates ribs during forceful breathing

Rhomboideus (Group)

• Origin: Spinous processes of C7 and T1-T5 vertebrae

• Insertion: Medial border of scapula

• Action:

  • Retracts and elevates scalpula

Serratus Anterior

• Origin: Outer surface of first 8 or 9 ribs

• Insertion: Ventral surface of scapula

• Action:

  • Protracts scapula

  • Rotates scapula

Supraspinatus

• Origin: Supraspinous fossa

• Insertion: Greater tubercle of humerus

• Action:

  • Abducts upper arm

Subscapularis

• Origin: Subscapular fossa

• Insertion: Lesser tubercle of humerus

• Action:

  • Extends upper arm

  • Rotates upper arm medially

Teres Major

• Origin: Lateral and medial borders of scapula

• Insertion: Intertubercular sulcus and lesser tubercle of humerus

• Action:

  • Extends shoulder

  • Adducts upper arm

  • Rotates upper arm medially

Teres Minor

• Origin: Lateral and medial borders of scapula

• Insertion: Greater tubercle of humerus

• Action:

  • Rotates upper arm laterally

Trapezius

• Origin: Occipital bone, spinous processes of cervical (C) and thoracic (T) vertebrae

• Insertion: Spine, acromion process of scapula; acromial end of clavicle

• Action:

  • Elevates, depresses, retracts, and rotates scapula

Abbreviations for Vertebrae

• C = cervical vertebrae

• L = lumbar vertebrae

• T = thoracic vertebrae

• S = sacral vertebrae

  • Example: C1-C4 represents cervical vertebrae 1-4.