Lab3 - Module 2 - Anatomy of the Arm and Forearm: Page 5 of 11

Muscles of the Flexor Forearm

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The flexor pronator group arises by a common flexor tendon from the medial epicondyle. This is called the common flexor origin. The deeper flexors originate from the anterior aspects of the bodies of the ulna and radius.

• All flexors - are located on the anterior surface of the wrist and most are held in place by the flexor retinaculum.

• The eight muscles of the anterior aspect of the forearm are flexors - can be considered in three functional groups: muscles that rotate the radius on the ulna (pronator teres and pronator quadratus); muscles that flex the hand at the wrist joint (flexor carpi radialis, palmaris longus, flexor carpi ulnaris); muscles that flex the digits (flexor digitorum superficialis, flexor digitorum profundus, flexor pollicis, longus).

• The anterior forearm muscles - can be divided into three layers: a superficial layer (pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris – this is the flexor pronator group that arises from a common tendon attached to the medial epicondyle of the humerus); an intermediate layer (flexor digitorum superficialis); and a deep layer (flexor digitrum profundus, flexor pollicis longus, pronator quadratus).

Deep group:

Add the Pronator Quadratus muscle.

Origin - Distal 1/4th of the anterior surface of the ulna

Insertion - Distal 1/4th of the anterior surface of the radius

Innervation - Anterior Interosseous Nerve from Median Nerve

Action - Pronates the hand

Add the Flexor Pollicus Longus muscle has two heads of origin; Radial Head and Humeral Head.

Origin - Anterior surface of the radius; it also arises from the interosseous membrane.

Insertion - Base of the distal phalanx of the thumb

Innervation - Anterior Interosseous Nerve from Median Nerve

Action - Flexion of the distal phalanx of the thumb and aids in thumb flexion

Add the Flexor Digitorum Profundus muscle.

Origin - Proximal 3/4ths of the anterior and medial aspects of the ulna and the ulnar half of the interosseous membrane

Insertion - Four long tendons at the base of the distal phalanx’s of the 4 medial fingers

Innervation - Lateral Part from Anterior Interosseous Nerve form Median Nerve and Medial Part from Ulnar Nerve

Action - Finger flexion at the distal interphalangeal joints, also aids in hand flexion at the wrist