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  5. Muscles of the pectoral girdle

11.5 Muscles of the pectoral girdle and upper limbs  (Page 3/76)

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Muscles that move the forearm

This multipart figure shows the different muscles that move the forearm. The major muscle groups are labeled.
The muscles originating in the upper arm flex, extend, pronate, and supinate the forearm. The muscles originating in the forearm move the wrists, hands, and fingers.

Muscles that move the forearm

This table describes the muscles that move the forearm. The biceps brachii are anterior muscles that perform a bicep curl; they also allow the palm of the hand to point toward the body while flexing. They originate in the coracoid process and the tubercle above the glenoid cavity. The brachialis originates in the front of the distal humerus. The brachioradialis is an anterior muscle that assists and stablizes the elbow during bicep-curl motion. It originates in the lateral supracondylar ridge at the distal end of the humerus. The triceps brachii are posterior muscles that extend the forearm, as during a punch. They originate in the infraglenoid tubercle of the scapula, the posterior shaft of the humerus, and the posterior humeral shaft distal to the radial groove. The aconeus is a posterior muscle that assists in extending the forearm; it also allows the forearm to extend away from the body. It originates in the lateral epicondyle of the humerus. The pronator teres is an anterior muscle that turns the hand palm-down. It originates in the medial epicondyle of the humerus and the coronoid process of the ulna. The pronator quadratus is an anterior muscle that assists in turning the hand palm-down. It originates in the distal portion of the anterior ulnar shaft. The supinator is a posterior muscle that turns the hand palm-down. It originates in the lateral epicondyle of the humerus and the proximal ulna.

Muscles that move the wrist, hand, and fingers

Wrist, hand, and finger movements are facilitated by two groups of muscles. The forearm is the origin of the extrinsic muscles of the hand    . The palm is the origin of the intrinsic muscles of the hand.

Muscles of the arm that move the wrists, hands, and fingers

The muscles in the anterior compartment of the forearm    (anterior flexor compartment of the forearm) originate on the humerus and insert onto different parts of the hand. These make up the bulk of the forearm. From lateral to medial, the superficial anterior compartment of the forearm    includes the flexor carpi radialis    , palmaris longus    , flexor carpi ulnaris    , and flexor digitorum superficialis    . The flexor digitorum superficialis flexes the hand as well as the digits at the knuckles, which allows for rapid finger movements, as in typing or playing a musical instrument (see [link] and [link] ). However, poor ergonomics can irritate the tendons of these muscles as they slide back and forth with the carpal tunnel of the anterior wrist and pinch the median nerve, which also travels through the tunnel, causing Carpal Tunnel Syndrome. The deep anterior compartment    produces flexion and bends fingers to make a fist. These are the flexor pollicis longus    and the flexor digitorum profundus    .

The muscles in the superficial posterior compartment of the forearm    (superficial posterior extensor compartment of the forearm) originate on the humerus. These are the extensor radialis longus    , extensor carpi radialis brevis    , extensor digitorum    , extensor digiti minimi    , and the extensor carpi ulnaris    .

The muscles of the deep posterior compartment of the forearm    (deep posterior extensor compartment of the forearm) originate on the radius and ulna. These include the abductor pollicis longus    , extensor pollicis brevis    , extensor pollicis longus    , and extensor indicis    (see [link] ).

Muscles that move the wrist, hands, and forearm

This table describes the muscles that move the wrist, hands, and forearm. These muscles make up the superficial anterior compartment of the forearm. The flexor carpi radialis bends the wrist toward the body; it also tilts the hand to the side away from the body. It originates in the medial epicondyle of the humerus. The palmaris longus assists in bending the hand up toward the shoulder. It originates in the medial epicondyle of the humerus. The flexor carpi ulnaris assists in bending the hand up toward the shoulder; it also tilts the hand to the side away from the body and stabilizes the wrist. It originates in the medial epicondyle of the humerus, the olecranon process, and the posterior surface of the ulna. The flexor digitorum superficialis bends the fingers to make a fist. It originates in the medial epicondyle of the humerus, the coronoid process of the ulna, and the shaft of the radius. These muscles make up the deep anterior compartment of the forearm. The flexor pollicis longus bends the tip of the thumb. It originates in the anterior surface of the radius and the interosseous membrane. The flexor digitorum profundus bends the fingers to make a fist; it also bends the wrist toward the body. It originates in the coronoid process, the anteromedial surface of the ulna, and the interosseous membrane. These muscles make up the superficial posterior compartment of the forearm. The extensor radialis longus straightens the wrist away from the body; it also tilts the hand to the side away from the body. It originates in the lateral supracondylar ridge of the humerus. The extensor carpi radialis brevis assists the extensor radialis longus in extending and abducting the wrist; it also stabilizes the hand during finger flexion. It originates in the lateral epicondyle of the humerus. The extensor digitorum opens the fingers and moves them sideways away from the body. It originates in the lateral epicondyle of the humerus. The extensor digiti minimi extends the little finger. It originates in the lateral epicondyle of the humerus. The extensor carpi ulnaris straightens the wrist away from the body; it also tilts the hand to the side toward the body. It originates in the lateral epicondyle of the humerus and the posterior of the ulna. These muscles make up the deep posterior compartment of the forearm. The abductor pollicis longus moves the thumb sideways toward the body; it also extends the thumb and moves the hand sideways toward the body. It originates in the posterior surface of the radius and ulna and in the interosseous membrane. The extensor pollicis brevis extends the thumb. It originates in the dorsal shaft of the radius and ulna and in the interosseous membrane. The extensor pollicis longus extends the thumb. It originates in the dorsal shaft of the radius and ulna and in the interosseous membrane. The extensor indicis extends the index finger; it also straightens the wrist away from the body. It originates in the posterior surface of the distal ulna and in the interosseous membrane.

The tendons of the forearm muscles attach to the wrist and extend into the hand. Fibrous bands called retinacula    sheath the tendons at the wrist. The flexor retinaculum    extends over the palmar surface of the hand while the extensor retinaculum    extends over the dorsal surface of the hand.

Intrinsic muscles of the hand

The intrinsic muscles of the hand    both originate and insert within it ( [link] ). These muscles allow your fingers to also make precise movements for actions, such as typing or writing. These muscles are divided into three groups. The thenar    muscles are on the radial aspect of the palm. The hypothenar    muscles are on the medial aspect of the palm, and the intermediate    muscles are midpalmar.

The thenar muscles include the abductor pollicis brevis    , opponens pollicis    , flexor pollicis brevis    , and the adductor pollicis    . These muscles form the thenar eminence    , the rounded contour of the base of the thumb, and all act on the thumb. The movements of the thumb play an integral role in most precise movements of the hand.
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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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