Fundamentals of Anatomy and Physiology

The Muscular System

Muscles Moving the Hand

Supination of the hand so that the palm is facing upward is
caused by the supinator (soo-pin-NAY-tohr) muscle. The
two muscles that pronate the hand so that the palm faces
downward are the pronator teres (pro-NAY-tohr TAYR-
eez) and the pronator quadratus (pro-NAY-tohr kwod-
RAH-tus). These muscles are found beneath the superficial
muscles deep in the arm. Table 9-6 lists

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the muscles that move the hand, thumb, and fingers and the

functions they perform.

Muscles Moving the Thumb

The thumb is capable of movement in many directions,

giving the hand a unique capability that separates hu-mans

from all other animals. We can grasp and use tools because

of our thumb. The two flexor pollicis (FLEKS-ohr

Table 9- 6 Muscles Moving the Hand, Thumb, and Fingers

Muscles Moving the Hand

Muscle Function

Supinator^ Supinates forearm^

Pronator teres^ Pronates forearm^

Pronator quadratus Pronates forearm

Muscles Moving the Thumb

Muscle Function

Flexor pollicis longus^ Flexes 2nd phalanx of thumb^

Flexor pollicis brevis^ Flexes thumb^

Extensor pollicis longus^ Extends terminal phalanx^

Extensor pollicis brevis^ Extends thumb^

Adductor pollicis^ Adducts thumb^

Abductor^ pollicis longus^ Abducts, extends thumb^

Abductor pollicis brevis^ Abducts thumb^

Opponens pollicis Flexes and opposes thumb

Muscles Moving the Fingers

Muscle Function

Flexor digitorum profundus^ Flexes terminal phalanx^

Flexor digiti minimi brevis^ Flexes little finger^

Interossei dorsalis^ Abduct, flex proximal phalanges^

Flexor digitorum superficialis^ Flexes middle phalanges^

Extensor indicis^ Extends index finger^

Interossei palmaris^ Adduct, flex proximal phalanges^

Abductor digiti minimi^ Abducts little finger^

Opponens digiti minimi^ Rotates, abducts 5th metacarpal^

Extensor digitorum communis Extends the fingers