Muscles of the Forearm

[Up] [extrinsicmm.] [intrinsicmm.] [arteries] [nerves] [Equine digit]

[joints]  [shoulder]  [brachium]  [image 1]  [image 2]  [image 3]  [image 4]

Often the best way to learn the muscles of the forearm is to start with the most cranial muscle on the lateral aspect of the forearm, work your way caudally on the lateral side, then back around cranially on the medial side.

The first muscle (A) lies against the radius and acts to extend the carpus, so why not call it the extensor carpi radialis muscle? The next muscle (B) extends all the digits and is, therefore, the common digital extensor muscle. Muscle C acts to extend only the lateral digits (III,IV,V), and so it is called the lateral digital extensor muscle. The next muscle, the ulnaris lateralis muscle (D), attaches to the accessory carpal bone and metacarpal IV and, therefore, flexes the carpus. In humans and some other species, however, the ulnaris lateralis muscle is an extensor of the carpus and is known as the extensor carpi ulnaris muscle. This explains why the ulnaris lateralis is innervated by the radial nerve, just like the extensor muscles of the carpus and digits. The most caudal muscle (E) is the flexor carpi ulnaris muscle. A larger head of the flexor carpi ulnaris muscle is found deep to this head and the adjacent superficial digital flexor muscle.

REMEMBER: If it doesn't have digital in the name, it doesn't act upon the digits!