Muscles of the Upper Limb

The **deltoid**is a thick, rounded muscle that forms the contours of the shoulder and serves as the primary abductor of the arm. Besides abduction, it aids in arm flexion, medial rotation, extension, and lateral rotation. Muscles that cross the shoulder joint and move the humerus involve both axial and scapular muscles, similar to the muscles that stabilize the **pectoral girdle**. The two axial muscles are the **pectoralis** major and the **latissimus dorsi**. The pectoralis major is a thick, fan-shaped muscle covering much of the upper portion of the **anterior thorax**. he broad, triangular latissimus dorsi is located on the lower back and inserts into a strong connective tissue sheath called an **aponeurosis**. The forearm, composed of the **radius** and **ulna bones**, performs four primary movements at the elbow joint: flexion, extension, pronation and supination. The **biceps brachii**, a two-headed muscle, crosses both the shoulder and elbow joints, allowing it to flex the forearm, aid in forearm supination at the **radioulnar joints**, contribute to flexing the arm at the shoulder joint. The **intrinsic muscles** of the hand both originate and insert entirely within the hand structure, enabling fine, precise movements necessary 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*