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– [Voiceover] Moving into the muscles that move the wrist, hands, and fingers. Now a few things about the
muscles of the forearm. When we start talking about
the muscles of the forearm, pretty much any of the muscles that start with the term flexor are to be found on the anterior side of the forearm. Pretty much any term that starts with the term extensor, is found back on the posterior side of the forearm. So keep that in mind as you start thinking about the muscles. Flexors of the forearm are
on the anterior surface. Extensors are on the posterior surface. The first muscle up,
flexor carpi radialis. Now, flexor carpi radialis, flexor tells us anterior side. Looking at radialis, means
on the radial, or thumb side. This muscle right here, with this tendon, is the flexor carpi radialis. For a little bit of orientation, this muscle is brachioradialis. This muscle is pronator teres, so this one right here is our flexor carpi radialis. Now the flexor carpi radialis
has two actions to know, or two primary actions at least. One action is going to
be flexion of the wrist. So flexor carpi radialis
causes flexion of the wrist. A second action is going
to be wrist abduction. So, A-B-duction. That means this one muscle can cause both flexion and abduction,
A-B-duction of the wrist. We move from the flexor
carpi radialis, over here. This next one down is going
to be palmaris longus. This is palmaris longus. Palmaris longus is going to cause a little bit of wrist flexion. It’s a weak flexor, but
primarily it’s going to tense the skin and the fascia of the hand. As your hand is moving,
the palmaris longus muscle is tensing the skin and the
fascia of the palm of you hands. Then we have the flexor carpi ulnaris. Here we have flexor carpi radialis. Palmaris longus. The one on the bottom, we
turn this a little bit. This one coming around is the flexor carpi ulnaris. Now, flexor carpi ulnaris will have again, flexion of the wrist,
but now it’s going to be antagonistic to the flexor carpi radialis. In that the flexor carpi
ulnaris can cause adduction. A-D-duction of the wrist. So the flexor carpi ulnaris can cause both flexion of the wrist
and adduction of the wrist. A-D-duction of the wrist. The flexor digitorum superficialis is a little bit deeper than
these superficial muscles. If you take this section off. So, we’re pulling off
flexor carpi radialis and palmaris longus, are all coming off. The muscle you see down
below that, right here. This muscle is going to be your flexor digitorum superficial. The flexor digitorum superficial is going to cause an
action of wrist flexion and also cause the middle phalanges of fingers two through five to flex. So we’re moving our wrist,
as in wrist flexion. But also, flexion of the middle phalanges of fingers two through five. Now if we go deep to the
flexor digitorum superficialis, we pull that off. We’re then going to see the
muscles the next layer down. The flexor digitorum profundus is this muscle you’re seeing under the yellow and the red here. Under the nerves and arteries. This is your flexor digitorum profundus. Now, the flexor digitorum profundus is going to allow for
flexion of the distal interphalangeal joints. The distal interphalangeal joints are basically the last
knuckle of your fingers. It’s right towards the end. So flexion of the distal
interphalangeal joints. Now, from there we can move on to the flexor pollicis longus. Same layer, but now
we’re on the thumb side. The flexor pollicis longus. The action of the flexor pollicis longus is flexes the distal phalanx of the thumb. Because pollicis, think pollex, thumb. The flexor pollicis longus flexes the distal interphalangeal joints. Turning the arm so we’re looking more at the posterior side here. We can start looking into the extensors of the forearm. For orientation, this muscle coming down around is the brachioradialis. To look at the extensor
carpi radialis longus, and extensor carpi radialis brevis. We’re looking at the two muscles that are right next to it. This one right here, right
next to the brachioradialis. This is the extensor
carpi radialis longus. It has a longer tendon. Well, this one is the extensor
carpi radialis brevis. A shorter tendon. Now both of these muscles, thankfully are sharing a similar action. The extensor carpi radialis longus, extensor carpi radialis brevis both can extend the wrist. They both also can help
out with abduction, A-B-duction of the wrist. That means the extensor
carpi radialis longus and extensor carpi radialis brevis both are causing abduction of the wrist. Just like flexor carpi radialis. So for that action,
abduction of the wrist. Those two are synergistic. But now, if we think about
the flexion extension. The extensor carpi
radialis longus and brevis are antagonistic to flexor carpi radialis. Now looking from a true posterior view, we have our extensor
carpi radialis longus. Extensor carpi radialis brevis. But then the next muscle
over is extensor digitorum. Now this muscle, extensor digitorum, is going to have an origin of the lateral epicondyle of the humerus. We’re coming up with the origin being up in here at
the lateral epicondyle. Its insertion go down
into the distal phalanges of fingers two through five. You can follow this down, follow the tendons, start to branch off into the fingers. The action of extensor digitorum is going to be extension of fingers two through five. With the innervation being the posterior interosseus nerve. The posterior interosseus nerve. It’s actually a branch
from the radial nerve. Now, if we continue on, right here. This is our extensor carpi ulnaris. You can see the extensor carpi ulnaris comes right down the posterior side. If I turn this just a
little bit, you can see the flexor carpi ulnaris. But this extensor carpi ulnaris is going to allow for
extension of the wrist. But it’s also allowing for ad,
A-D, adduction of the wrist. That means, if we’re
talking about the action of adduction of the wrist,
the flexor carpi ulnaris and as well as the extensor carpi ulnaris. So the flexor and extensor carpi ulnaris are going to be synergistic
for the adduction of the wrist. But then, because one’s a
flexor, one’s an extensor, they’re antagonistic
for flexion, extension. Our next muscle is going
to be a deeper muscle. Now, because it is on the deeper side, we cannot see it in the
model we’ve been using. So we’re moving into this figure here. This muscle right here
is the extensor indicis. Now the extensor indicis, you can see how the tendon is going to
run right up through here. So, just like the name sounds and implies, the extensor indicis will
extend the index finger. So extensor indicis extends index finger. The extensor pollicis longus
muscle is a deeper muscle. We can at least see the tendon right here. Coming out and running to the thumb. The tendon, all the way back to there, then it runs underneath. The tendon of the
extensor pollicis longus. While we were able to see the tendon of the extensor pollicis
longus, we couldn’t really see the entire muscle belly. So, by looking into this diagram, which has a deeper view, you can see this muscle right here, is your extensor pollicis longus. We saw this tendon on the model. But now we can see the
entire muscle belly. Extensor pollicis longus. And to give a little orientation, this muscle right next to it is the extensor indicis. This is your extensor pollicis longus. The action of extensor pollicis longus. The action is going to
be, extends the thumb. Makes sense, extensor pollicis longus. Extends the thumb. Next muscle up is the
abductor, A-B-ductor, abductor pollicis longus. The abductor pollicis longus
is this muscle right here. These are two muscles, this is the brevis. This is the longus. Abductor pollicis longus. Again, the tendon comes right up and runs right into the thumb. The abductor, so
A-B-ductor pollicis longus, is going to abduct, or A-B-duct the thumb. But can also help to extend the thumb. The abductor pollicis longus. Now that we’ve turned the
model around a little bit, we’re looking at the
anterior side of the hand. The palm side. We have our thenar muscles group. This is our thenar muscles group. Pretty much the muscles
in the ball of the thumb. Now there are several
different muscles there. And they all have their
own individual actions. But as a whole the thenar muscle group really controls quite a bit
of movement for the thumb. The next group of muscles
is the hypothenar muscles. This group of muscles is the muscles that are around the fifth digit, or the little finger. Their actions are going to help with movement of the fifth digit. The fifth phalange. And the third group is going to be the muscles that are in
the palm of the hand. Again, there are several
different muscles in here. But their main action is to help with movement of the fingers. The midpalmar muscles, midpalmar. Right in the middle of the palm. So our three groups
are the thenar muscles, the midpalmar muscles and
the hypothenar muscles.

14 thoughts on “Muscles That Move the Wrist Hand Fingers

  1. You are great! Thanks for the good work. I really appreciate how slow you explain it, it's very didatic. Regards from Brazil.

  2. thank you soo much, the explanation was very clear and not too fast, as a radiology resident i find it very helpful!

  3. Out of curiosity, how would turning the wrist so that if you were holding a stick it went from being upright to horizontally aligned (a 90 degree turn to the left when looking at the arm in this video) affect the alignment of these muscles in the forearm and and the upper arm? I would think that the vertical position aligns muscles so that the tricep is dominant and the other for the bicep.

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