from the muscles of the forelimb. It is "up in the air". The brachioradialis is a synergistic muscle to the biceps brachii, because it flexes the forelimb. Running along this muscle is the radial nerve.
The five muscles on the surface of the forearm from lateral to medial are: extensor carpi radialis, pronator teres, flexor carpi radialis, palmaris longus, and the barely visible flexor carpi ulnaris.
The "carpi" muscle flex and extend the carpus. The palmaris longus flexes the wrist, and the pronator teres pronates the limb.
Examine the pronator teres to note that its fibers extend from the ulna to the radius in such a way that contraction of the muscle will draw the radius across the ulna: pronation!
On the lateral/posterior surface you will again see six muscles and the radial nerve. The muscle next to the nerve is the brachioradialis which can be seen on the cat from both sides.
The five other muscles from lateral to medial are: extensor carpi radialis (it too is visible from both sides), extensor digitorum communis, extensor digitorum lateralis, extensor carpi ulnaris, and again the barely visible flexor carpi ulnaris.
The "digitorum" muscles extend the digits (phalanges) and the "carpi" muscles extend and flex the wrist.
Once you have mastered these muscles on the cat you should have no major problems learning them on a human. However, note the following differences between the cat and the human:
1. The extensor carpi radialis may be hidden on the anterior surface by the brachioradialis of the human.
2. The deep flexor digitorum superficialis is visible in the distal anterior forearm.
3. In the posterior view the brachioradialis is not as easily visible.
4. There are two extensor carpi radialis muscles in the human: extensor carpi radialis longus and extensor carpi radialis brevis.
5. The extensor muscles for the digits have different names in the human. They are the lateral extensor digitorum and the medial extensor digiti minimi.
Examine the model of the human arm and locate all of the muscles discussed in this chapter.
Label the drawings in Figure 18.1.
Figure 18.1 Muscles of the Arm
Biceps brachii Brachioradialis Deltoid (X2) Extensor carpi radialis brevis Extensor carpi radialis longus
Extensor carpi ulnaris Extensor digit! minimi Extensor digitorum Flexor carpi radialis Flexor carpi ulnaris (X2)
Flexor digitorum superficialis Palmaris longus Pronator teres Triceps brachii
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