The Forearm

Muscles of the forearm are described in Tables 12-16 to 12-18 and depicted in Figure 12-25.

TABLE 12-14 Elbow Extensor Muscles*

Muscles

Origin (Proximal Attachment)

Insertion (Distal Attachment)

Innervation Action

Triceps brachii

Anconeus

Long head: infraglenoid tubercle of scapula Lateral head: posterior surface of humerus, superior to radial groove Medial head: posterior surface of humerus, inferior to radial groove Lateral epicondyle of humerus

Proximal end of olecranon ulna and fascia of forearm

Radial nerve (C6-C8)

Lateral surface of olecranon and superior part of posterior surface of ulna

Extends forearm; long head stabilizes head of abducted humerus

Radial nerve (C7-T1)

Assists triceps in extending forearm; stabilizes elbow joint; abducts ulna during pronation

*See Figure 12-23.

Acromion

Trapezius Infraspinatus Teres minor Teres major

Latissimus dorsi

Acromion

Dorsal interossei

Anconeus

Extensor carpi ulnaris

Figure 12-23 Elbow extensor muscles.

Anconeus

Extensor carpi ulnaris

Triceps brachii

Brachioradialis

Extensor carpi radialis longus Extensor carpi radialis brevis Extensor digitorum

Dorsal interossei

Figure 12-23 Elbow extensor muscles.

TABLE 12-15 Elbow Supinator Muscle*

Muscles

Origin (Proximal

Insertion (Distal

Innervation

Action

Attachment)

Attachment)

Supinator

Lateral epicondyle of humerus,

Lateral, posterior, and

Deep branch of

Supinates forearm

radial collateral and annular

anterior surfaces of

radial nerve

(rotates radius

ligaments, supinator fossa,

proximal third of

(C5 and C6)

to turn palm

and crest of ulna

radius

anteriorly)

*See Figure 12-24.

*See Figure 12-24.

Humerus

Brachioradialis Biceps brachii Bicipitial aponeurosis

Radial collateral ligament Radial nerve, deep branch Biceps brachii, tendon Supinator Pronator teres Flexor carpi radialis

Radius

Pronator quadratus

Flexor carpi radialis, tendon

Humerus

Median nerve

Palmaris longus Ulna

Flexor carpi ulnaris, tendon

Figure 12-24 Supinator and pronator muscles

Median nerve

Palmaris longus Ulna

Flexor carpi ulnaris, tendon

Figure 12-24 Supinator and pronator muscles

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