Muscles of the Upper Limb

The **deltoid**, the thick muscle that creates the rounded lines of the shoulder is the major abductor of the arm, but it also facilitates flexing and medial rotation, as well as extension and lateral rotation. Similar to the muscles that position the **pectoral girdle**, muscles that cross the shoulder joint and move the humerus bone of the arm include both axial and scapular muscles. The two axial muscles are the **pectoralis** major and the **latissimus dorsi**. The pectoralis major is thick and fan-shaped, covering much of the superior portion of the **anterior thorax**. The broad, triangular latissimus dorsi is located on the inferior part of the back, where it inserts into a thick connective tissue shealth called an **aponeurosis**. The forearm, made of the **radius** and **ulna bones**, has four main types of action at the hinge of the elbow joint: flexion, extension, pronation, and supination. The **two-headed biceps** brachii crosses the shoulder and elbow joints to flex the forearm, also taking part in supinating the forearm at the **radioulnar joints** and flexing the arm at the shoulder joint. The **intrinsic muscles** of the hand both originate and insert within it. These muscles allow your fingers to also make precise movements for actions, such as typing or writing.



*LICENSES AND ATTRIBUTIONS

CC licensed content, Shared previously, Appendicular Muscles of the Pelvic Girdle and Lower Limbs, Authored by: OpenStax College. License: CC BY: Attribution. License Terms: Download for free at http://cnx.org/contents/y9_gDy74@3/Appendicular-Muscles-of-the-Pe*