I meant to spend tonight going through several of the forearm plates in Richer’s Anatomy book, and also drawing them mirror-image since I seem to get hung up on left-right issues when studying the limbs. Seemed like a good plan, but as I started on the first diagram I realized how poorly I understood the flexors, and so spent several hours just going over them, talking them through, trying to make sense of them. Forget the whole forearm. Just take one small bite out of it. The flexor group is plenty complicated for a night’s study.
Basically it boils down to this: there are six flexor muscles, five of which are visible or affect the surface; they all originate from a common tendon at the medial epicondyle of the humerus. ALL FLEXORS ORIGINATE FROM THIS POINT. Going from the thumb side of the inner wrist to the little finger, there are four: flexor carpi radialis on the thumb side, and flexor carpi ulnaris on the little finger side (which is actually very large and wraps around to the back as well). Next to the radialis is the palmeris longus (which apparently about 1 in 11 people lack, and a few people have two), and then the flexor digitorum superficialis, which inserts to all four fingers, but the visible tendon is the ring finger one; the others are below or under the palmeris longus. Although it’s the smallest of the four on the surface, it is massive underneath, and also accounts for the “in between” space of the other subcutaneous flexors. The fifth flexor is the pronator teres, up high by the inner elbow and crossing strongly over the flexor carpi radialis and disappearing under the brachioradialis, which is in the ridge group and we’ll get to it later.
The sixth flexor is the flexor digitorum profundus, which is the biggest muscle of the forearm and pretty much unseen, except for along the back of the ulna in some cases (though it’s still thinly covered by the flexor carpi ulnaris). It’s the main “gripping muscle”, and although it’s not seen directly, it’s under all of the others and so it affects the surface form in that way.
Six flexors. The flexor digitorum profundus is largely invisible; the pronator teres goes its own way up high by the elbow; the other four are, from thumb side to little finger side: flexor carpi radialis (the largest on the surface), palmeris longus, flexor digitorum superficialis, and flexor carpi ulnaris (which wraps around to the back as well).
That, just that, is plenty of study for one night. I will try to recall this through the workday tomorrow. Once I feel like I’ve got it, and can see them on people, THEN it’s time to move on to the extensors, and then to the ridge group. One small section at a time, learned thoroughly, rather than all 15 forearm muscles crammed on and memorized but poorly understood. Slow down. This shit is complicated.