1.7 Intrinsic Muscles of the Thoracic Limb: Craniolateral Muscles of the Forearm

Craniolateral Muscles of the Forearm

Extensor carpi radialis

Common digital extensor

Lateral digital extensor

Ulnaris lateralis/extensor carpi ulnaris

Supinator

Extensor carpi obliquus

Brachioradialis

name the craniolateral muscles of the forearm (7)

Extensor carpi radialis

• the most medial member of the group

• situated cranially into the subcutaneous border of the radius. It inserts on the proximal extremity of the 3rd metacarpal bone (sometimes in 2nd MC bone)

• Origin: lateral supracondylar crest

• Insertion: proximal extremity of the 3rd metacarpal bone

• Action: to extend the carpal joint

• Innervation: Radial nerve

Common digital extensor

• long muscle inserting on the extensor process of the distal phalanges of each functional digits

• Origin: lateral epicondyle of the humerus

• Insertion: extensor process of the distal phalanges of each functional digits

• Action: to extend the joints of the 4 principal digits

• Innervation: Radial nerve

Lateral digital extensor

• originates from the proximal end of the radius and inserting on the lateral digits.

• Origin: lateral epicondyle of the humerus

• Insertion: proximal ends of the phalanges digits 3 to 5

• Action: to extend the carpus and joints of the digits

• Innervation: Radial nerve

Ulnaris lateralis/extensor carpi ulnaris

• the most caudal extensor muscle

• Origin: lateral epicondyle of the humerus

• Insertion: it inserts on the proximal part of metacarpal bone and accessory carpal bone

• Action: to abduct and rotate the carpal joint laterally

• Innervation: Radial nerve

Supinator

• small, fusiform muscle placed deep to the extensor muscles and passing obliquely over the flexor aspect of the elbow from the lateral epicondyle to the upper quarter of the medial border of the radius.

• Origin: lateral epicondyle of the humerus

• Insertion: cranial surface of the proximal 4th of the radius

• Action: to rotate the forearm laterally

• Innervation: Radial nerve

Extensor carpi obliquus

• also known as abductor pollicis longus, originates from the cranial surface of the radius and by the oblique medio-distal course pursued by its tendon, which attaches to the most medial metacarpal bone present.

• It functions as the extensor of the carpus; in dogs and cats, for medial deviation of the paw.

• Origin: cranial surface of the ulna

• Insertion: proximal end of metacarpal 1

• Action: To extend the digit 1

• Innervation: Radial nerve

Brachioradialis

• Also known as long supinator is a thin fleshy ribbon that extends from the lateral epicondyle of humerus to the distal medial part of the forearm within the superficial fascia.

• Origin: lateral epicondylar crest of the humerus

• Insertion: periosteum of the radius

• Action: to rotate the radius craniolaterally

• Innervation: Radial nerve