Ferret antebrachium
Text and photos: Catherine Lenox and Victoria Clayton
superficial, lateral muscles of the ferret antebrachium, anterior (craniad) to left of photo
superficial, medial muscles of the ferret antebrachium
| Muscle | Origin | Insertion | Action |
| Extensor carpi ulnaris | lateral epicondyle of the humerus | digit V | extends the carpus (wrist) |
| Extensor digitorum lateralis | lateral surface of the humerus proximal to the lateral epicondyle | digit IV and V | extends digits |
| Extensor digitorum communis | lateral surface of the humerus proximal to the lateral epicondyle | Splits to insert on digits II, III, IV, and V | entends digits |
| Brachioradialis (supinator longus) | humerus proximal to the lateral epicondylar ridge | styloid porcess of the radius | extends forearm |
| Extensor carpi radialis longus | lateral surface of the humerus proximal to the lateral epicondyle | metacarpal of digit II | extends forepaw |
| Extensor carpi radialis brevis | Lateral surface of the humerus proximal to the lateral epicondyle | Metacarpal of digit III | extends forepaw |
| Abductor pollicis longus | Radius and ulna | Radial side of thumb (digit I) | Extends and abducts thumb |
| Pronator teres | Medial epicondyle of the humerus | Radius | Pronates forepaw |
| Flexor carpi radialis | Medial epicondyle of the humerus | Metacarpals of digits II and III | Flexes wrist |
| Palmaris longus | Medial epicondyle of the humerus | Skin of the paw | Flexes digits |
| Flexor digitorum superficialis | Medial epicondyle of the humerus | Distal phalanx of digits I through V | Flexes digits |
| Flexor digitorum profundus | Medial epicondyle of the humerus | Distal phalanx of digits I through V | Flexes digits |
| Flexor carpi ulnaris | Multiple heads from humerus and olecranon process of ulna | Accessory carpal bone | Flexes forearm |
Adapted from Klingener (1979)
The ferret is a plantigrade quadruped with five digits on each paw. They have thick footpads to aid in locomotion. They have the ability to pronate their forearms, but this is not a specialized feature in the ferret.
The forearm of the animal had been skinned during a previous lab but the forepaw had not. This was a difficult task that required the footpads be removed. Once the skin was removed, the forearm muscles were easily separated. A tough retinaculum at the wrist was removed to observe the underlying tendons and their insertions. The retinaculum is a band of thick connective tissue that runs transversely across the wrist [2]. It braces the tendons of the muscles that flex and extend the digits. The retinaculum was removed by making a cut parallel to the tendons to avoid damaging them. Once this was completed, the muscles were easily identified.
The muscles of the forearm can be divided into a dorsal extensor group and a ventral flexor group. The dorsal extensor group was comprised of six muscles: the brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum communis, extensor digitorum lateralis, and the extensor carpi ulnaris. All of these muscles were approximately the same length, although the brachioradialis was slightly shorter than the other five muscles. Despite their similar lengths, these muscles were different widths. The brachioradialis was the thickest muscle, while the extensor carpi radialis brevis was the narrowest. The remaining four muscles were approximately the same width. All extensor muscles originated at or just proximal to the lateral epicondyle of the humerus, though they inserted into different digits. The extensor digitorum communis was especially interesting. This muscle inserted in all four fingers while others inserted into only one or two digits. Once the extensor retinaculum was severed, all of the superficial tendons of the dorsal side of the hand were connected to this muscle. The abductor pollicis longus, also on the dorsal side of the forearm, was deeper than all other extensor muscles. This muscle extends the thumb, while the other extensor muscles extend the fingers.
The ventral flexor group includes five muscles. They are the pronator teres, flexor carpi radialis, flexor digitorum profundus, palmaris longus, and the flexor carpi ulnaris. The extensor carpi radialis could be seen on the medial side of the forearm, deep to the flexor muscles. The flexor carpi ulnaris was on the lateral edge of the ulnar side of the forearm, which made it more visible in the lateral view than the medial view. This muscle was also of special note because it originates from multiple heads on the humerus and the olecranon process. The pronator teres runs between the humerus and the radius and is involved in pronation of the forearm. This was the only pronator or suppinator found in the dissection. The pronator teres was approximately the same size as the other flexor muscles. The ferret is able to pronate the forearm to some extent, though not to the same degree as the cat. The degree of pronation found in the ferret explains the medium size of the pronator teres. The flexor digitorum profundus and superficialis inserted on all five digits. The tendons of the flexor digitorum superficialis split at the first joint of the phalanges and inserted into both sides of the digit. At this point, the tendons of the flexor digitorum profundus became visible as they emerged from beneath the flexor digitorum superficialis tendons. These tendons continued to the distal end of the phalanges. The flexors were of approximately equal size, and were also about the same size as the extensors.
The dorsal side of the manus did not have intrinsic musculature. The palm of the hand does have two muscles, the palmaris brevis and the abductor pollicis brevis. However, it was difficult to identify these muscles due to their small size.
1. Fox, J.G. 1998. Biology and Diseases of the Ferret (2nd Ed.). Williams & Wilkins, Baltimore.
2. Klingener, D. 1980. Laboratory Anatomy of the Mink (2nd Ed.). William C. Brown, Dubuque, Iowa.